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8 pages, 182 KiB

Open AccessEditorial

Oil and Gas Well Engineering Measurement and Control

by Tianshou Ma and Yuqiang Xu

Processes 2024, 12(5), 1034; https://doi.org/10.3390/pr12051034 - 20 May 2024

Viewed by 1837

Abstract

Oil and gas wells represent a unique channel in regard to oil and gas exploration and production [...] Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

Research

Jump to: Editorial

25 pages, 12052 KiB

Open AccessArticle

Fluid-Loss Control Technology: From Laboratory to Well Field

by Shamil Islamov, Ravil Islamov, Grigory Shelukhov, Anar Sharifov, Radel Sultanbekov, Rustem Ismakov, Akhtyam Agliullin and Radmir Ganiev

Processes 2024, 12(1), 114; https://doi.org/10.3390/pr12010114 - 2 Jan 2024

Cited by 14 | Viewed by 1730

Abstract

Effective fluid-loss control in oil wells is a critical concern for the oil industry, particularly given the substantial reserves situated in carbonate reservoirs globally. The prevalence of such reservoirs is expected to rise with the slow depletion of hydrocarbons, intensifying the need to [...] Read more.

Effective fluid-loss control in oil wells is a critical concern for the oil industry, particularly given the substantial reserves situated in carbonate reservoirs globally. The prevalence of such reservoirs is expected to rise with the slow depletion of hydrocarbons, intensifying the need to address challenges related to deteriorating reservoir properties post well-killing operations. This deterioration results in significant annual losses in hydrocarbon production at major oil enterprises, impacting key performance indicators. To tackle this issue, this study focuses on enhancing well-killing technology efficiency in carbonate reservoirs with abnormally low formation pressures. To address this issue, the authors propose the development of new blocking compositions that prevent the fluid loss of treatment fluids by the productive reservoir. The research tasks include a comprehensive analysis of global experience in well-killing technology; the development of blocking compositions; an investigation of their physico-chemical, rheological, and filtration properties; and an evaluation of their effectiveness in complicated conditions. The technology’s application in the oil and gas condensate fields of the Volga-Ural province showcases its practical implementation. This study provides valuable insights and solutions for improved fluid-loss control in carbonate reservoirs, ultimately enhancing well performance and hydrocarbon recovery. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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19 pages, 3993 KiB

Open AccessArticle

Experimental Tests on In Situ Combustion Using Dynamic Ignition Simulation System in High-Temperature and High-Pressure Conditions

by Yuchuan Yin, Xinyuan Chen, Xiaocong Yu, Deji Liu, Chao Chen, Xiaosong Zhou, Xiaohui Li, Lidong Zhang and Changbin Kan

Processes 2024, 12(1), 52; https://doi.org/10.3390/pr12010052 - 25 Dec 2023

Cited by 1 | Viewed by 914

Abstract

The study of crude oil oxidation characteristics is fundamental to the design of ignition in situ combustion. Experimentation is the most crucial method for studying the oxidation characteristics of crude oil. Aiming to address the challenges posed by high temperature, high pressure, and [...] Read more.

The study of crude oil oxidation characteristics is fundamental to the design of ignition in situ combustion. Experimentation is the most crucial method for studying the oxidation characteristics of crude oil. Aiming to address the challenges posed by high temperature, high pressure, and rapid temperature changes during the combustion of crude oil, a dynamic simulation system for high-temperature and high-pressure ignition is designed. In order to study the oxidation characteristics of the crude oil ignition process, we conducted experiments using a high-temperature and high-pressure dynamic ignition simulation device. The experiments focused on determining the ignition point of crude oil under different pressure conditions, oil–water ratios, heating rates, gas injection rates, and other relevant characteristics. The kinetic model for the oxidation process of crude oil ignition was established. The kinetic parameters were calculated for different ignition conditions and the apparent activation energy for each oxidation stage was determined. Additionally, the stability of in situ combustion was evaluated under various ignition parameters. The results show that the Arrhenius curves for crude oil exhibit noticeable differences in the HTO (high-temperature oxidation) and LTO (low-temperature oxidation) regions. The curves demonstrate good linearity in the HTO region, with correlation coefficients exceeding 0.9. Moreover, the apparent activation energies in the HTO region range from 8.01 to 26.7 kJ/mol. The apparent activation energies and finger front factors were calculated for the HTO stage under different pressure conditions. The results showed that, as the pressure increased, the autoignition point, inflection point temperature, and apparent activation energy of the crude oil decreased. This suggests that increasing the pressure can enhance the HTO of the crude oil. The spontaneous ignition point of the crude oil exhibited an upward trend as the heating rate increased. Additionally, the maximum temperature during the combustion process generally increased with the heating rate, reaching a maximum temperature of 453.1 °C. The tests demonstrated that the simulation system is capable of real-time monitoring and recording of oxidation parameters during the combustion process of crude oil. This system can provide essential data for project implementation and numerical simulation. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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17 pages, 6270 KiB

Open AccessArticle

A New Experimental Method for Acid Pretreatment in Perforated Horizontal Wells: A Case Study of Mahu Conglomerate Reservoir

by Wenting Jia, Jianye Mou, Guifu Wang, Xiaowei Li, Xinliang Wang and Xinfang Ma

Processes 2023, 11(12), 3353; https://doi.org/10.3390/pr11123353 - 2 Dec 2023

Cited by 1 | Viewed by 1303

Abstract

The Mahu Oilfield in Xinjiang, China, is the world’s largest conglomerate oilfield, with a daily output of more than 8000 tons. In the fracturing of perforated horizontal wells, the breakdown pressure is high, resulting in difficulties in their treatment. Acid pretreatment has been [...] Read more.

The Mahu Oilfield in Xinjiang, China, is the world’s largest conglomerate oilfield, with a daily output of more than 8000 tons. In the fracturing of perforated horizontal wells, the breakdown pressure is high, resulting in difficulties in their treatment. Acid pretreatment has been applied to reduce the breakdown pressure in the field, but with poor performance. Few studies have been conducted on how acid pretreatment affects the breakdown pressure under perforation conditions in the Mahu conglomerate reservoir. Also, existing fracturing or acid pretreatment experiments cannot simulate perforation well. Therefore, a new method was developed to make perforations by hydro jetting the fracturing specimens (300 mm × 300 mm × 300 mm) first. It can achieve specified perforation parameters, including the perforation angle, position, and length. Subsequently, true triaxial hydraulic fracturing experiments were conducted on the conglomerate specimens obtained from the Mahu area. The effects of the acid pretreatment on the fracture initiation and breakdown pressure were investigated by injecting the perforation section of the conglomerate using various acid systems. The study results showed that the perforation made by the new apparatus was extremely close to the perforation on-site. The acid pretreatment effectively dissolved minerals and could decrease the breakdown pressure down to 7.7 MPa. A combination of 6%HF + 10%HCl was recommended for the acid pretreatment in the Mahu conglomerate reservoir. A total of 60 min acid–rock contact time is necessary for sufficient rock dissolution. The mechanism of the acid pretreatment to decrease the breakdown pressure is that the rock dissolution by the acid reduces the rock tensile strength and increases the permeability. The raised permeability increases the fluid pressure of the reservoir near the wellbore so as to reduce the breakdown pressure of the formation. The research results provide technical support for reducing construction difficulty and optimizing parameters in the Mahu Oilfield. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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27 pages, 7520 KiB

Open AccessArticle

Numerical Simulation Analysis of Wellbore Integrity and Casing Damage in High-Temperature Injection and Production of Shale Oil

by Xiaocong Yu, Xueqi Cen, Changbin Kan, Yilin Hu, Yanxing Yang, Shilin Tao, Xinyuan Chen, Xiupeng Chen and Zhiqiang Hu

Processes 2023, 11(11), 3053; https://doi.org/10.3390/pr11113053 - 24 Oct 2023

Viewed by 1994

Abstract

Shale oil represents a relatively new form of unconventional oil and gas resource, and the extensive exploration and development of shale oil resources carry significant implications for China’s oil and gas supply and demand dynamics. At present, within the realm of low-maturity shale [...] Read more.

Shale oil represents a relatively new form of unconventional oil and gas resource, and the extensive exploration and development of shale oil resources carry significant implications for China’s oil and gas supply and demand dynamics. At present, within the realm of low-maturity shale oil extraction technologies, the reservoir must be subjected to elevated temperatures ranging between 400 to 60 °C. Prolonged exposure of wellbores to such high temperatures can result in a substantial decrease in cement strength, the formation of microcracks due to cement cracking, and damage stemming from thermal stresses on the casing. Casing damage stands out as a prominent factor contributing to wellbore integrity failures and well shutdowns within the context of shale oil development. Given the limited natural energy reservoirs of shale oil formations, it becomes necessary to supplement the reservoir’s energy during the development process. Furthermore, shale oil exhibits high viscosity and poor flowability, and conventional water injection methods yield limited efficacy. This situation can induce significant shifts in the stress field and rock mechanical parameters, potentially activating specific formations and complicating the load dynamics on the casing. Consequently, the risk of failure increases. In light of these considerations, this study uses numerical simulations to study the integrity of high-temperature injection and production wellbores in shale oil and aims to encompass a comprehensive evaluation and analysis of the principal factors that influence casing damage, the fluctuations in thermal stress, and the yield strength of various steel grades of casings exposed to alternating stress conditions. Subsequently, this paper developed a model for simulating the temperature and pressure within shale oil and steam injection wellbores to support engineering design analysis. The research results indicate that the application of pre-stress results in a significant increase in stress at the casing pipe head while causing a noticeable decrease in stress within the pipe wall. When N80 casing is used, the entire casing experiences thermal stresses surpassing the casing’s yield limit. Stress concentration may arise at both ends of the external seal, potentially leading to casing contraction, shear failure, and, under non-uniform stress conditions, casing bending deformation. The temperature of steam injection significantly influences the temperature field of the casing wall, with stress values experiencing a marked reduction when the steam injection temperature decreases from 350 °C to 200 °C, underscoring the substantial impact of temperature on casing thermal stress. As the steam injection process advances along with injection-production cycles, shear stresses at the interface can exceed the bond strength, resulting in relative slippage between the cement and the casing. The bonding force between the wellbore and the cement primarily depends on the interface’s friction, particularly in the context of friction during wellhead lifting. This study endeavors to determine rational injection and production parameters under varying conditions, optimize completion methods, reduce casing damage, and extend the casing’s operational life; it aims to offer critical technical support for the safe and efficient development of shale oil resources. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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17 pages, 18384 KiB

Open AccessArticle

Stick–Slip Characteristics of Drill Strings and the Related Drilling Parameters Optimization

by Chao Wang, Wenbo Chen, Zhe Wu, Jun Li and Gonghui Liu

Processes 2023, 11(9), 2783; https://doi.org/10.3390/pr11092783 - 18 Sep 2023

Cited by 6 | Viewed by 1786

Abstract

To eliminate or reduce stick–slip vibration in torsional vibration of the drilling string and improve the rate of penetration (ROP), a stick–slip vibration model of the drilling string considering the ROP was established based on the multidimensional torsional vibration model of the drilling [...] Read more.

To eliminate or reduce stick–slip vibration in torsional vibration of the drilling string and improve the rate of penetration (ROP), a stick–slip vibration model of the drilling string considering the ROP was established based on the multidimensional torsional vibration model of the drilling string. The model was verified by simulation analysis. The characteristics of the drilling string stick–slip vibration in the three stages of stationary, slip, and stick were analyzed. This paper investigated the influence of rotary torque, rotary speed, and weight on bit (WOB) on stick–slip vibrations in the drill string. Based on this, the relationship between the drilling parameters and ROP was established. Drilling parameter optimization was completed for soft, medium-hard, and hard formations. Results showed that appropriately increasing torque and decreasing WOB can reduce or even eliminate stick–slip vibrations in the drill string and increase the ROP. The parameter optimization increased the ROP by 11.5% for the soft formation, 13.7% for the medium-hard formation, and 14.3% for the hard formation. The established drill string stick–slip vibration model provides theoretical guidance for optimizing drilling parameters in different formations. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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17 pages, 3653 KiB

Open AccessArticle

Prediction of Lost Circulation in Southwest Chinese Oil Fields Applying Improved WOA-BiLSTM

by Xianming Liu, Wen Jia, Zhilin Li, Chao Wang, Feng Guan, Kexu Chen and Lichun Jia

Processes 2023, 11(9), 2763; https://doi.org/10.3390/pr11092763 - 15 Sep 2023

Cited by 5 | Viewed by 1291

Abstract

Drilling hazards can be significantly decreased by anticipating potential mud loss and then putting the right well control measures in place. Therefore, it is critical to provide early estimates of mud loss. To solve this problem, an enhanced WOA (Whale Optimization Algorithm) and [...] Read more.

Drilling hazards can be significantly decreased by anticipating potential mud loss and then putting the right well control measures in place. Therefore, it is critical to provide early estimates of mud loss. To solve this problem, an enhanced WOA (Whale Optimization Algorithm) and a BiLSTM (Bidirectional Long Short Term Memory) optimization based prediction model of lost circulation prior to drilling has been created. In order to minimize the noise in the historical comprehensive logging data, a wavelet filtering technique was first used. Then, according to the nonlinear Spearman rank correlation coefficient between mud loss and logging parameter values from large to small, seven characteristic parameters were preferred, and the sliding window was used to extract the relevant data. Secondly, the number of neurons in the first and second hidden layers, the maximum training time, and the initial learning rate of the BiLSTM model were optimized using the enhanced WOA method. The BiLSTM network was given the acquired superparameters in order to improve the model’s ability to predict occurrences. Finally, the model was trained and tested using the processed data. In comparison to the LSTM model, BiLSTM model, and WOA-BiLSTM model, respectively, the improved WOA-BiLSTM early mud loss prediction in southwest Chinese oil fields suggested in this study beat the others, receiving 22.3%, 18.7%, and 4.9% higher prediction accuracy, respectively. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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14 pages, 4132 KiB

Open AccessArticle

Prediction of Leakage Pressure during a Drilling Process Based on SSA-LSTM

by Dong Chen, Baolun He, Yanshu Wang, Chao Han, Yucong Wang and Yuqiang Xu

Processes 2023, 11(9), 2608; https://doi.org/10.3390/pr11092608 - 1 Sep 2023

Cited by 1 | Viewed by 1181

Abstract

Drilling-fluid loss has always been one of the challenging issues in the field of drilling engineering. This article addresses the limitations of a single fluid-loss pressure mechanism model and the challenges in predicting positive drilling-fluid-loss pressure. By categorizing fluid losses of various types [...] Read more.

Drilling-fluid loss has always been one of the challenging issues in the field of drilling engineering. This article addresses the limitations of a single fluid-loss pressure mechanism model and the challenges in predicting positive drilling-fluid-loss pressure. By categorizing fluid losses of various types encountered during drilling, different geological formations associated with distinct mechanisms are considered. The actual drilling-fluid density in the wellbore at the time of fluid-loss occurrence is taken as a reference value for calculating the positive drilling-fluid-loss pressure of the already drilled well. Building upon this foundation, a combined model utilizing the Sparrow Search Algorithm (SSA) and Long Short-Term Memory (LSTM) neural network is constructed. This model effectively explores the intricate nonlinear relationship between well logging, logging engineering data, and fluid-loss pressure. By utilizing both data from the already drilled wells and upper formation data from ongoing drilling, precise prediction of positive drilling formation fluid-loss pressure can be achieved. Case studies demonstrate that the approach established in this paper, incorporating upper formation data, reduces the average absolute percentage error of fluid-loss pressure prediction to 2.4% and decreases the root mean square error to 0.0405. Through the synergy of mechanistic models and data-driven techniques, not only has the accuracy of predicting positive drilling formation fluid-loss pressure has been enhanced, but also valuable insights have been provided for preventing and mitigating fluid losses during drilling operations. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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17 pages, 3703 KiB

Open AccessArticle

Research on Managed-Pressure Running Casing in Oil and Gas Wells with the Negative Pressure Window

by Yuntao Mei, Huanqiang Yang, Zhuo Zhang and Mengjia Ji

Processes 2023, 11(7), 2210; https://doi.org/10.3390/pr11072210 - 22 Jul 2023

Viewed by 1881

Abstract

The failure of managed-pressure running casing in oil and gas wells may lead to complex accidents such as overflow or leakage. The technique of using multi-density gradient drilling fluids in wellbores with negative pressure windows (NPWs) is often used to deal with this [...] Read more.

The failure of managed-pressure running casing in oil and gas wells may lead to complex accidents such as overflow or leakage. The technique of using multi-density gradient drilling fluids in wellbores with negative pressure windows (NPWs) is often used to deal with this situation. Therefore, it is vital to analyze the dynamic slurry column structure and calculate the wellbore pressure during casing running. For this issue, the model of transient surge pressure is established during casing running. The calculation equation of the model is proposed, and the calculations of the wellbore pressure are carried out with the exploration of Well LT-X1, located in the Xinjiang oil field. A circulation scheme is designed as follows: Circulate 125 m³ of drilling fluid with a density of 2.45 g/cm³ and 155 m³ of drilling fluid with a density of 2.35 g/cm³ at a depth of 3560 m. From there, circulate 164 m³ of drilling fluid with a density of 2.35 g/cm³ at a depth of 5900 m. Finally, at a depth of 7050 m, circulate 250 m³ of drilling fluid with a density of 2.30 g/cm³. The casing running speeds and back-pressure values were designed as follows for the respective well sections: 0–1523 m: 0.160 m/s casing speed, 0 MPa back pressure; 1523–3560 m: 0.160 m/s casing speed, 1.641 MPa back pressure; 3560–5900 m: 0.145 m/s casing speed, 2.427 MPa back pressure; 5900–6674 m: 0.137 m/s casing speed, 4.041 MPa back pressure; 6674–7050 m: 0.124 m/s casing speed, 4.457 MPa back pressure. The results show that optimizing structure of the multi-density gradient drilling fluid with different densities and applying annular back pressure in stages, with the accurate calculation of wellbore pressure, can achieve the goals of leak-proofing and pressure-stabilization. It is concluded that this result may serve as the foundation for managed-pressure running casing technology. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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20 pages, 7539 KiB

Open AccessArticle

A Novel Pattern Recognition based Kick Detection Method for Offshore Drilling Gas Kick and Overflow Diagnosis

by Yang Xu, Jin Yang, Zhiqiang Hu, Dongsheng Xu, Lei Li and Chao Fu

Processes 2023, 11(7), 1997; https://doi.org/10.3390/pr11071997 - 3 Jul 2023

Cited by 1 | Viewed by 1538

Abstract

In offshore drilling, accidents such as gas invasion, overflow, and kicks are unavoidable, and they can escalate into blowouts and other catastrophic events, resulting in casualties and significant economic losses. Therefore, ensuring drilling safety requires precise monitoring of gas invasion and overflow. Currently, [...] Read more.

In offshore drilling, accidents such as gas invasion, overflow, and kicks are unavoidable, and they can escalate into blowouts and other catastrophic events, resulting in casualties and significant economic losses. Therefore, ensuring drilling safety requires precise monitoring of gas invasion and overflow. Currently, most overflow monitoring methods used at drilling sites are based on threshold criteria. However, the monitoring parameters obtained during actual drilling operations often contain noise signals, which makes it challenging for threshold-based methods to achieve a balance between improving accuracy and minimizing false positives. This paper proposes a novel method called Pattern-Recognition-based Kick Detection (PRKD) for diagnosing overflow in offshore drilling. The PRKD method utilizes the overflow evolution process by integrating multiphase flow calculations, data filtering theory, pattern recognition theory, the Bayesian framework, and other theoretical models. By analyzing the shape and wave characteristics of the curves, PRKD effectively detects and monitors gas intrusion and overflow based on single parameters. Through case analysis, it is demonstrated that the proposed method achieves high precision in monitoring drilling overflow while maintaining a low false positive rate. By combining advanced computational techniques with pattern recognition algorithms, PRKD improves the accuracy and reliability of kick detection, enabling proactive responses to potential risks, protecting the environment and human lives, and optimizing drilling operations. The case analysis shows that by integrating the probabilistic information of pre-drilling kicks and various characteristic parameters, when the noise amplitude is less than 8 L/s, the PRKD model exhibits superior detection performance. Moreover, when the noise amplitude is 16 L/s, the PRKD model detects the continuous overflow approximately 200 s after the actual overflow occurs and predicts a 95.8% probability of overflow occurrence at the specified location, meeting the on-site requirements. The gas invasion monitoring method proposed in this paper provides accurate diagnostic results and a low false positive rate, offering valuable guidance for gas invasion monitoring in drilling operations. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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25 pages, 14874 KiB

Open AccessArticle

Finite-Element Analysis on Energy Dissipation and Sealability of Premium Connections under Dynamic Loads

by Yang Yu, Yinping Cao, Zhan Qu, Yihua Dou and Zidi Wang

Processes 2023, 11(7), 1927; https://doi.org/10.3390/pr11071927 - 26 Jun 2023

Cited by 3 | Viewed by 1289

Abstract

In the process of high flow rate fracture and high gas production, the sealing performance of the premium connection decreases due to the dynamic load and vibration of downhole tubing strings, which may cause accidents. Existing static analysis methods cannot effectively explain this [...] Read more.

In the process of high flow rate fracture and high gas production, the sealing performance of the premium connection decreases due to the dynamic load and vibration of downhole tubing strings, which may cause accidents. Existing static analysis methods cannot effectively explain this phenomenon. The main objective of this paper is to propose a novel analytical method for evaluating the sealing performance of a premium connection. In this paper, a dynamic model of sealing surfaces of the premium connection is established based on the vibration equation of elastic rod, and the hysteresis characteristics and energy dissipation mechanism of sealing surfaces are analyzed. Considering the influence of spherical radius, internal pressure, axial cyclic load amplitude, and modal vibration, a spherical-conical premium connection finite element model is established to analyze the influence laws of the connection’s energy dissipation and sealing performance. The results show that the sealing performance of the premium connection under dynamic load can be effectively analyzed by using energy dissipation theory compared with traditional static contact analysis. Compared with the vibration of the tubing string, the dynamic loads caused by the change of fluid pressure and flow rate in the tubing string have a significant influence on the connection’s sealing performance. When the internal pressure and axial cyclic loads are 80 MPa, 400 kN, or 60 MPa and 500 kN respectively, serious plastic deformation occurs in the thread and sealing surfaces, and the energy dissipation of the sealing surfaces increases significantly, which could lead to sealing failure. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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17 pages, 4108 KiB

Open AccessFeature PaperArticle

Blank Strip Filling for Logging Electrical Imaging Based on Multiscale Generative Adversarial Network

by Qifeng Sun, Naiyuan Su, Faming Gong and Qizhen Du

Processes 2023, 11(6), 1709; https://doi.org/10.3390/pr11061709 - 2 Jun 2023

Cited by 5 | Viewed by 1510

Abstract

The Fullbore Formation Micro Imager (FMI) represents a proficient method for examining subterranean oil and gas deposits. Despite its effectiveness, due to the inherent configuration of the borehole and the logging apparatus, the micro-resistivity imaging tool cannot achieve complete coverage. This limitation manifests [...] Read more.

The Fullbore Formation Micro Imager (FMI) represents a proficient method for examining subterranean oil and gas deposits. Despite its effectiveness, due to the inherent configuration of the borehole and the logging apparatus, the micro-resistivity imaging tool cannot achieve complete coverage. This limitation manifests as blank regions on the resulting micro-resistivity logging images, thus posing a challenge to obtaining a comprehensive analysis. In order to ensure the accuracy of subsequent interpretation, it is necessary to fill these blank strips. Traditional inpainting methods can only capture surface features of an image, and can only repair simple structures effectively. However, they often fail to produce satisfactory results when it comes to filling in complex images, such as carbonate formations. In order to address the aforementioned issues, we propose a multiscale generative adversarial network-based image inpainting method using U-Net. Firstly, in order to better fill the local texture details of complex well logging images, two discriminators (global and local) are introduced to ensure the global and local consistency of the image; the local discriminator can better focus on the texture features of the image to provide better texture details. Secondly, in response to the problem of feature loss caused by max pooling in U-Net during down-sampling, the convolution, with a stride of two, is used to reduce dimensionality while also enhancing the descriptive ability of the network. Dilated convolution is also used to replace ordinary convolution, and multiscale contextual information is captured by setting different dilation rates. Finally, we introduce residual blocks on the U-Net network in order to address the degradation problem caused by the increase in network depth, thus improving the quality of the filled logging images. The experiment demonstrates that, in contrast to the majority of existing filling algorithms, the proposed method attains superior outcomes when dealing with the images of intricate lithology. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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17 pages, 4549 KiB

Open AccessArticle

A Method of Reducing Friction and Improving the Penetration Rate by Safely Vibrating the Drill-String at Surface

by Yuan Long, Xueying Wang, Peng Wang and Feifei Zhang

Processes 2023, 11(4), 1242; https://doi.org/10.3390/pr11041242 - 17 Apr 2023

Cited by 6 | Viewed by 2554

Abstract

Drill-string axial vibration at the surface technology is proposed to reduce the friction between the drill-string and the borehole wall, and to improve load transfer efficiency, the rate of penetration (ROP), and the extended-reach limit of a horizontal well. An analytical framework utilizing [...] Read more.

Drill-string axial vibration at the surface technology is proposed to reduce the friction between the drill-string and the borehole wall, and to improve load transfer efficiency, the rate of penetration (ROP), and the extended-reach limit of a horizontal well. An analytical framework utilizing the “soft-string” model is constructed. The results obtained from numerical simulations reveal that during the slide drilling operation, the drill-string experiences an axial stick–slip motion, and the weight on bit (WOB) undergoes periodic oscillations. The conventional calibration method of the WOB in the weight indicator gauge is not applicable when the ROP is low. After applying axial vibration on the drill-string at the surface, the WOB increases and becomes smooth because of a release of friction. The amplitude and frequency of the exciting force are the main factors affecting surface vibration effectiveness. There is an optimal frequency for a given case (10 Hz in this paper). This means that the conventional manual pick-up and slack-off by drillers with a high amplitude and a low frequency has little effect on friction reduction. In addition, the conventional method can bring in high risk because of its high root mean square (RMS) acceleration. Safety evaluation results indicate that the drill-string is in a safe state under most of the exciting parameters. The results verify the feasibility and advantages of the proposed technology, and lay a solid theoretical foundation for its application in real drilling applications. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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17 pages, 3689 KiB

Open AccessArticle

A Three-Dimensional Analytical Solution of Stress Field in Casing-Cement-Stratum System Considering Initial Stress State

by Xiaoyang Wang, Tingxue Jiang, Yayun Zhang, Jun Zhou, Hecheng Xiao and Wenda Li

Processes 2023, 11(4), 1164; https://doi.org/10.3390/pr11041164 - 10 Apr 2023

Cited by 1 | Viewed by 1410

Abstract

Accurate stress field calculation of the casing-cement-stratum system is crucial for evaluating wellbore integrity. Previous models treated in-situ stress as boundary pressure loads, leading to unrealistic infinite displacements at infinity. This study presents a three-dimensional (3D) analytical solution for the stress field within [...] Read more.

Accurate stress field calculation of the casing-cement-stratum system is crucial for evaluating wellbore integrity. Previous models treated in-situ stress as boundary pressure loads, leading to unrealistic infinite displacements at infinity. This study presents a three-dimensional (3D) analytical solution for the stress field within the casing-cement-stratum system in inclined wells, considering in-situ stress and hydrostatic stress in cement as the initial stress state and taking into account stress components related to the axial direction. Assuming a plane strain condition and superimposing the in-plane plane strain problem, elastic uni-axial stress problem and anti-plane shear problem, a 3D analytical solution is obtained. Comparisons with previous models indicate that the existing model overestimates the absolute values of stress components and failure potential of casing and cement in both 2D and 3D scenarios. The presence of initial stress in cement greatly increases the absolute value of the compressive stress state but decreases the failure potential in cement, which has not been well studied. Additionally, a low Young’s modulus and high initial stress state of the cement benefits the cement’s integrity since the maximum Mises stress significantly decreases. The new 3D analytical solution can provide a benchmark for 3D numerical simulation and quick assessment for wellbore integrity. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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19 pages, 11011 KiB

Open AccessArticle

Analysis of Bottomhole Rock Stress in Deep-Well Drilling Considering Thermal-Hydro-Mechanical Coupling

by Bin Yang and Honglin Xu

Processes 2023, 11(3), 683; https://doi.org/10.3390/pr11030683 - 23 Feb 2023

Cited by 3 | Viewed by 1747

Abstract

Drilling is a key step in the exploitation of deep oil and gas resources. In order to clarify the stress state of the rocks and the mechanism of rock breakage in deep-well drilling, a thermal-hydro-mechanical coupling model for deep-well drilling was established, and [...] Read more.

Drilling is a key step in the exploitation of deep oil and gas resources. In order to clarify the stress state of the rocks and the mechanism of rock breakage in deep-well drilling, a thermal-hydro-mechanical coupling model for deep-well drilling was established, and the effects of drilling on the temperature, pressure, and stress in the formation were studied. Furthermore, the effects of the formation parameters and wellbore parameters on the bottomhole stress were analyzed. The results revealed that after the formation was drilled, the temperatures in different horizontal in situ stress directions were not significantly different, but the difference in the pore pressure between the maximum and minimum horizontal stress directions was large. The average effective stress at the bottom of the hole was the smallest, and in some areas, it was tensile stress. For deep-well drilling, as the formation pressure increased, the in situ stress increased, and the permeability decreased, leading to greater average effective stress of the bottomhole rock. As a result, it was harder to break the rock, and the drilling efficiency decreased. Reducing the wellbore pressure and wellbore temperature is conducive to forming tensile stress near the borehole axis in the bottomhole, causing tensile damage. The average effective stress of the formation near the shoulder of the drill bit was compressive stress, and it is advisable to take advantage of the rock shear failure characteristics to improve the drilling efficiency in this area. The results of this study can help us to understand the stress state of the bottomhole rocks and the mechanism of rock breakage and can provide a reference for the optimization of drilling tools and drilling parameters in deep-well drilling. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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19 pages, 10917 KiB

Open AccessArticle

Numerical Simulation and Field Test Research on Vibration Reduction of PDC Cutting of Pebbled Sandstone under Composite Impact Load

by Heng Zhang, Hongjian Ni, Henglin Yang, Li Fu, Yuan Wang, Shubin Liu, Bin Huang, Zixin Wang and Gang Chen

Processes 2023, 11(3), 671; https://doi.org/10.3390/pr11030671 - 22 Feb 2023

Cited by 1 | Viewed by 1664

Abstract

Downhole vibrations caused by rock breaking when drilling through pebbled sandstone formations negatively affect the rate of penetration (ROP) and the safety of downhole tools. Therefore, it is of great significance to study the cutting characteristics of pebbled sandstone and find a method [...] Read more.

Downhole vibrations caused by rock breaking when drilling through pebbled sandstone formations negatively affect the rate of penetration (ROP) and the safety of downhole tools. Therefore, it is of great significance to study the cutting characteristics of pebbled sandstone and find a method of reducing the drilling vibrations of pebbled sandstone formations. Based on the DEM (discrete element method), a simulation model of pebbled sandstone considering the random filling of high-strength gravels was established by using the random polygon distribution method. The influence of gravel content on the strength parameters and the breaking state of the pebbled sandstone samples was analyzed. Additionally, a DEM model of PDC cutting rocks loaded by a spring–mass system was established, and the Stribeck effect of contact friction between the PDC cutter and the rock was analyzed. The periodic vibration and the stick–slip phenomenon of the cutting system during the drilling process were presented by this model. The model was employed to simulate and explore the influence of composite impact load on stick–slip vibration during PDC cutting of pebbled sandstone. The simulation results showed that the composite impact load had a more obvious effect on mitigating the vibration of PDC cutting of pebbled sandstone under the condition of a higher horizontal impact amplitude coefficient (q_h = 40%). Based on the simulation results, a composite impactor with a large impact angle α = 70° was selected to conduct the field tests in the pebbled sandstone formation of Well T1. The results showed that, compared to conventional drilling, the average WOB (weight on bit) of the section drilled with the composite impactor decreased by 57.13%, the standard deviation of the WOB decreased by 57.29%, and the average ROP increased by 98.31%. The employing of composite impactors in pebbled sandstone formations can significantly reduce drilling vibration, improve ROP, and protect bits and downhole instruments. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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17 pages, 3623 KiB

Open AccessArticle

Effects of Make-Up Torque on the Sealability of Sphere-Type Premium Connection for Tubing and Casing Strings

by Bin Yang, Honglin Xu, Shilin Xiang, Zhi Zhang, Kanhua Su and Yan Yang

Processes 2023, 11(1), 256; https://doi.org/10.3390/pr11010256 - 12 Jan 2023

Cited by 7 | Viewed by 2614

Abstract

The present investigations on sealability evaluation for tubing and casing premium connections depend on the FEM with testing. This paper proposed a theoretical model to evaluate the sealability of a sphere-type premium connection based on make-up torque, which combines Hertz contact pressure and [...] Read more.

The present investigations on sealability evaluation for tubing and casing premium connections depend on the FEM with testing. This paper proposed a theoretical model to evaluate the sealability of a sphere-type premium connection based on make-up torque, which combines Hertz contact pressure and the von Mises yield criterion for calculating elastic–plastic contact pressure distribution on sealing interface and adopts the gas sealing criterion obtained from Murtagian’s experimental results for deducing gas sealing capacity. With the proposed model, the effects of additional make-up torque from the sealing interface on the sealing contact pressure distribution and key sealability parameters, including contact width, yield width, average contact pressure and gas sealing capacity, were analyzed and compared. The results show that additional make-up torque from the sealing interface closely influenced sealability parameters’ variation and gas sealing capacity. The gas sealing index based on the sealing contact energy theory should be recommended for sealability evaluation other than average contact pressure on the sealing interface. For improving gas sealability, make-up torque should be controlled accurately for ensuring enough average contact pressure and contact width but a proper yield width, and a lager sphere radius should be selected for reducing the risk of yield sticking. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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15 pages, 2767 KiB

Open AccessArticle

Optimization of the Lateral Length of Shale-Gas Horizontal Wells Based on Geology–Engineering–Economy Integration

by Jialin Zhu, Sha He and Lin Lin

Processes 2023, 11(1), 249; https://doi.org/10.3390/pr11010249 - 12 Jan 2023

Cited by 4 | Viewed by 3203

Abstract

Horizontal wells with extended lateral lengths and large-scale hydraulic fracturing are a key technology for shale gas development. Lateral length is the key factor in determining the production and economic benefits of horizontal wells. Therefore, based on geology–engineering–economy integration, a method for optimizing [...] Read more.

Horizontal wells with extended lateral lengths and large-scale hydraulic fracturing are a key technology for shale gas development. Lateral length is the key factor in determining the production and economic benefits of horizontal wells. Therefore, based on geology–engineering–economy integration, a method for optimizing the lateral length of shale-gas horizontal wells is established. Through fracture-shape prediction, productivity simulation and input–output analysis, the net present-value model of the technical–economic evaluation of the economic lateral length is established. A comprehensive evaluation of lateral lengths in Changning Block is then conducted. The results show that, under the current geological, engineering, and economic conditions in Changning Block, a horizontal well with a lateral length between 175 m and 3508 m is economically viable, and the optimal economic lateral length is 2000 m. The porosity and thickness of the reservoir matrix, the production time, the drilling investment, and the price of the natural gas wellhead in the first year have a great impact on the economic lateral length. On one hand, we can increase the drilling rate by increasing the technical research and development efforts. On the other hand, we can improve the construction management level to reduce investment and reasonably increase the price subsidy to optimize the lateral length of shale-gas horizontal wells. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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19 pages, 3973 KiB

Open AccessArticle

Finite Element and Neural Network Models to Forecast Gas Well Inflow Performance of Shale Reservoirs

by Reda Abdel Azim and Abdulrahman Aljehani

Processes 2022, 10(12), 2602; https://doi.org/10.3390/pr10122602 - 5 Dec 2022

Cited by 2 | Viewed by 1663

Abstract

Shale gas reservoirs are one of the most rapidly growing forms of natural gas worldwide. Gas production from such reservoirs is possible by using extensive and deep well fracturing to contact bulky fractions of the shale formation. In addition, the main mechanisms of [...] Read more.

Shale gas reservoirs are one of the most rapidly growing forms of natural gas worldwide. Gas production from such reservoirs is possible by using extensive and deep well fracturing to contact bulky fractions of the shale formation. In addition, the main mechanisms of the shale gas production process are the gas desorption that takes place by diffusion of gas in the shale matrix and by Darcy’s type through the fractures. This study presents a finite element model to simulate the gas flow including desorption and diffusion in shale gas reservoirs. A finite element model is used incorporated with a quadrilateral element mesh for gas pressure solution. In the presented model, the absorbed gas content is described by Langmuir’s isotherm equation. The non-linear iterative method is incorporated with the finite element technique to solve for gas property changes and pressure distribution. The model is verified against an analytical solution for methane depletion and the results show the robustness of the developed finite element model in this study. Further application of the model on the Barnett Shale field is performed. The results of this study show that the gas desorption in Barnett Shale field affects the gas flow close to the wellbore. In addition, an artificial neural network model is designed in this study based on the results of the validated finite element model and a back propagation learning algorithm to predict the well gas rates in shale reservoirs. The data created are divided into 70% for training and 30% for the testing process. The results show that the forecasting of gas rates can be achieved with an R² of 0.98 and an MSE = 0.028 using gas density, matrix permeability, fracture length, porosity, PL (Langmuir’s pressure), VL (maximum amount of the adsorbed gas (Langmuir’s volume)) and reservoir pressure as inputs. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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17 pages, 2618 KiB

Open AccessArticle

Neural Network Model for Permeability Prediction from Reservoir Well Logs

by Reda Abdel Azim and Abdulrahman Aljehani

Processes 2022, 10(12), 2587; https://doi.org/10.3390/pr10122587 - 4 Dec 2022

Cited by 4 | Viewed by 3689

Abstract

The estimation of the formation permeability is considered a vital process in assessing reservoir deliverability. The prediction of such a rock property with the use of the minimum number of inputs is mandatory. In general, porosity and permeability are independent rock petrophysical properties. [...] Read more.

The estimation of the formation permeability is considered a vital process in assessing reservoir deliverability. The prediction of such a rock property with the use of the minimum number of inputs is mandatory. In general, porosity and permeability are independent rock petrophysical properties. Despite these observations, theoretical relationships have been proposed, such as that by the Kozeny–Carmen theory. This theory, however, treats a highly complex porous medium in a very simple manner. Hence, this study proposes a comprehensive ANN model based on the back propagation learning algorithm using the FORTRAN language to predict the formation permeability from available well logs. The proposed ANN model uses a weight visualization curve technique to optimize the number of hidden neurons and layers. Approximately 500 core data points were collected to generate the model. These data, including gamma ray, sonic travel time, and bulk density, were collected from numerous wells drilled in the Western Desert and Gulf areas of Egypt. The results show that in order to predict the permeability accurately, the data set must be divided into 60% for training, 20% for testing, and 20% for validation with 25 neurons. The results yielded a correlation coefficient (R²) of 98% for the training and 96.5% for the testing, with an average absolute percent relative error (AAPRE) of 2.4%. To validate the ANN model, two published correlations (i.e., the dual water and Timur’s models) for calculating permeability were used to achieve the target. In addition, the results show that the ANN model had the lowest mean square error (MSE) of 0.035 and AAPRE of 0.024, while the dual water model yielded the highest MSE of 0.84 and APPRE of 0.645 compared to the core data. These results indicate that the proposed ANN model is robust and has strong capability of predicting the rock permeability using the minimum number of wireline log data. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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10 pages, 5148 KiB

Open AccessArticle

Study on the Erosion of Choke Valves in High-Pressure, High-Temperature Gas Wells

by Ling Guo, Yayong Wang, Xiaohui Xu, Han Gao, Hong Yang and Guoqing Han

Processes 2022, 10(10), 2139; https://doi.org/10.3390/pr10102139 - 20 Oct 2022

Cited by 3 | Viewed by 3056

Abstract

During the process of gas production in high-pressure, high-temperature (HPHT) gas wells, the choke valve, as the most vital component of the surface control equipment, plays a significant role in regulating the output and reducing the fluid pressure to ensure the safety of [...] Read more.

During the process of gas production in high-pressure, high-temperature (HPHT) gas wells, the choke valve, as the most vital component of the surface control equipment, plays a significant role in regulating the output and reducing the fluid pressure to ensure the safety of surface gathering and transportation equipment. High-pressure, high-velocity fluid flow and solid-phase particles cause deterioration of the choke valve. With the enhancement of intelligent and digital oilfields, conventional choke valves have been progressively replaced by electric choke valves. Due to the complex structure of the throttle valve, the flow path and the velocity state of the fluid in the throttle valve, and the distribution law of the erosion fraction are quite distinctive from those in the ordinary throttle valve, meriting further research. In this paper, a simulation of computational fluid dynamics (CFD) was conducted to determine the effects of the pressure distribution, fluid state, divergent particle sizes, and sand volume on the erosion rate of the choke valve. Under various valve openings, the fluid state and the location of high-risk points can be ascertained. The large particle size (diameter greater than 6 mm) of sand and gravel is convenient for causing concentrated erosion in the position of the valve hole, which induces the channel diameter to expand. Fine silt sand (diameter from 0.1 mm to 1 mm) gives rise to relatively uniform abrasion to the choke’s current-facing surface. This study can optimize the layout of the choke valve and reduce the cost and number of switching wells, thereby decreasing the frequency of maintenance and the pressure fluctuation’s effect on the formation. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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18 pages, 7033 KiB

Open AccessArticle

Wellbore Temperature and Pressure Calculation of Offshore Gas Well Based on Gas–Liquid Separated Flow Model

by Jun Jing, Hongbin Shan, Xiaohua Zhu, Yixiang Huangpu and Yang Tian

Processes 2022, 10(10), 2043; https://doi.org/10.3390/pr10102043 - 10 Oct 2022

Cited by 8 | Viewed by 4326

Abstract

Compared with land wells, the production environment and reservoir depth of offshore oil and gas wells are more complex and shallower. Further, HPHT production fluid there will produce strong temperature and pressure disturbance that affects the wellbore, which easily generates wellbore safety problems, [...] Read more.

Compared with land wells, the production environment and reservoir depth of offshore oil and gas wells are more complex and shallower. Further, HPHT production fluid there will produce strong temperature and pressure disturbance that affects the wellbore, which easily generates wellbore safety problems, such as wellhead growth and leakage caused by the incompatible deformation of casing and cement sheath. Therefore, obtaining an accurate wellbore temperature and pressure field is the key to implementing a wellbore safety assessment. Based on the gas–liquid two-phase separated method, this paper established an improved calculation model of wellbore temperature and pressure field for offshore HPHT wells. This model also takes into account the heat transfer environment characteristics of “formation-seawater-air” and the influence of well structure. Compared with the measured data of the case well, the error of temperature and pressure calculation results of the improved model are only 0.87% and 2.46%. Further, its calculation accuracy is greatly improved compared to that of the traditional gas–liquid homogeneous flow calculation model. Based on this model, the influencing factors of wellbore temperature and pressure in offshore gas wells are analyzed. The results show that forced convection heat exchange between seawater–air and wellbore is stronger than that between wellbore and formation. Reducing the gas–liquid ratio of the product can effectively reduce wellbore temperature and increase wellbore pressure. The gas production has a significant impact on the wellbore temperature. When the gas production rises from 10

\times 10^{4} \cdot m^{3} / d

to 60

\times 10^{4} \cdot m^{3} / d

, the wellhead temperature rises from 63

° C

to 99

° C

. However, due to the mutual influence of friction pressure drop and hydrostatic pressure drop, wellbore pressure increases first and then decreases with the increase in gas production. The improved model can provide a more accurate estimate of the time to reach the rated wellhead temperature. Meanwhile, this model displays accurate theoretical support for the rational formulation of the production plan after the well opening, so as to avoid excessive restrictions on the initial production rate. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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15 pages, 3895 KiB

Open AccessArticle

Optimizing the Gamma Ray-Based Detection System to Measure the Scale Thickness in Three-Phase Flow through Oil and Petrochemical Pipelines in View of Stratified Regime

by Abdulilah Mohammad Mayet, Tzu-Chia Chen, Seyed Mehdi Alizadeh, Ali Awadh Al-Qahtani, Abdullah K. Alanazi, Nivin A. Ghamry, Hala H. Alhashim and Ehsan Eftekhari-Zadeh

Processes 2022, 10(9), 1866; https://doi.org/10.3390/pr10091866 - 15 Sep 2022

Cited by 6 | Viewed by 1666

Abstract

As the oil and petrochemical products pass through the oil pipeline, the sediment scale settles, which can cause many problems in the oil fields. Timely detection of the scale inside the pipes and taking action to solve it prevents problems such as a [...] Read more.

As the oil and petrochemical products pass through the oil pipeline, the sediment scale settles, which can cause many problems in the oil fields. Timely detection of the scale inside the pipes and taking action to solve it prevents problems such as a decrease in the efficiency of oil equipment, the wastage of energy, and the increase in repair costs. In this research, an accurate detection system of the scale thickness has been introduced, which its performance is based on the attenuation of gamma rays. The detection system consists of a dual-energy gamma source (²⁴¹ Am and ¹³³ Ba radioisotopes) and a sodium iodide detector. This detection system is placed on both sides of a test pipe, which is used to simulate a three-phase flow in the stratified regime. The three-phase flow includes water, gas, and oil, which have been investigated in different volume percentages. An asymmetrical scale inside the pipe, made of barium sulfate, is simulated in different thicknesses. After irradiating the gamma-ray to the test pipe and receiving the intensity of the photons by the detector, time characteristics with the names of sample SSR, sample mean, sample skewness, and sample kurtosis were extracted from the received signal, and they were introduced as the inputs of a GMDH neural network. The neural network was able to predict the scale thickness value with an RMSE of less than 0.2, which is a very low error compared to previous research. In addition, the feature extraction technique made it possible to predict the scale value with high accuracy using only one detector. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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20 pages, 5809 KiB

Open AccessArticle

Mechanism Analysis and Potential Solutions for Casing Deformation of Shale GAS Fracturing Wells in Sichuan Basin

by Bihua Xu, Shuo Yang, Bin Yuan, Lu Ma and Leding Wang

Processes 2022, 10(9), 1711; https://doi.org/10.3390/pr10091711 - 27 Aug 2022

Cited by 8 | Viewed by 2969

Abstract

Casing deformation caused by fault and fracture sliding derived from fracturing has attracted growing attention. Casing deformation frequently occurs during the hydraulic fracturing process in the Sichuan Basin. Although its mechanism has been intensively studied, this issue is becoming increasingly severe and demands [...] Read more.

Casing deformation caused by fault and fracture sliding derived from fracturing has attracted growing attention. Casing deformation frequently occurs during the hydraulic fracturing process in the Sichuan Basin. Although its mechanism has been intensively studied, this issue is becoming increasingly severe and demands immediate solutions, especially in the shale gas blocks of Changning-Weiyuan-Zhaotong. The present study summarizes and analyzes the research progress relevant to casing deformation based on the existing literature. It is shown that the casing deformation rate of the deflection point on the shale gas horizontal well is much higher than that of other places and that shear deformation is the dominant form. The main factors influencing the casing deformation of shale gas horizontal wells include weakened strength of the collapsing casing, geological factors, cement, cement quality sheath, fracturing engineering factor, etc. We propose to reduce casing deformation by optimizing well trajectory, improving casing strength and cementing quality or optimizing fracturing operation. In addition, a hierarchical relationship between the influencing factors is also provided. However, the mechanisms of some forms of casing deformation need to be further studied, and the casing deformation in shale gas exploitation must be solved urgently. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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9 pages, 2684 KiB

Open AccessArticle

Movement Law of Methane Drained by Large-Diameter Borehole Drilling Machine in the Goaf

by Yun Lei

Processes 2022, 10(9), 1669; https://doi.org/10.3390/pr10091669 - 23 Aug 2022

Cited by 4 | Viewed by 1431

Abstract

To study the movement law of methane in the goaf drained by a large-diameter borehole drilling machine under “U”-shaped ventilation, a simulation on a coal mine was conducted on Fluent to find the optimal spacing between large-diameter boreholes and the most appropriate distance [...] Read more.

To study the movement law of methane in the goaf drained by a large-diameter borehole drilling machine under “U”-shaped ventilation, a simulation on a coal mine was conducted on Fluent to find the optimal spacing between large-diameter boreholes and the most appropriate distance between the borehole and the upper corner. The variation of borehole drilling and the methane concentration in the upper corner were obtained through a field test. Results show that the method of drilling large-diameter boreholes greatly reduces the methane concentration in the goaf and the upper corner, with the optimal borehole spacing being 30 m and the most appropriate distance between the borehole and the upper corner being 15 m. When the large-diameter borehole is drilled 25 m deep down into the goaf, it penetrates into the stress impact area, and the methane concentration increases rapidly, with the maximum being 3.7%. When the borehole is drilled 35 m down into the goaf, the methane concentration slightly decreases as a result of the drainage superposition effect. The methane concentration in the upper corner increases as the borehole is drilled deeper and is farther away from the upper corner. As a result of the drainage superposition effect, the methane concentration in the upper corner varies from 0.32% to 0.51% in a cyclical way. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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23 pages, 13199 KiB

Open AccessArticle

Design of Downhole Robot Actuator System and Mechanical Behavior Analyses of the PRSM by Considering Elastic Errors and Radial Loads

by Xuelian Dong, Haiyan Zhu, Qingyou Liu, Qiaozhu Wang and Xingming Wang

Processes 2022, 10(8), 1520; https://doi.org/10.3390/pr10081520 - 2 Aug 2022

Cited by 4 | Viewed by 1768

Abstract

This paper designs a new class of actuators for the downhole traction robot system to achieve high-accuracy transmission, which is realized by the planetary roller screw mechanism (PRSM). As the downhole environment is a non-structure one, which increases the difficulty of the load [...] Read more.

This paper designs a new class of actuators for the downhole traction robot system to achieve high-accuracy transmission, which is realized by the planetary roller screw mechanism (PRSM). As the downhole environment is a non-structure one, which increases the difficulty of the load analyses and distributions of the downhole robot system to complete a predesigned mission. Traditional achievements about the mechanical behavior analyses of PRSM ignore the effects of radial loads and torque elastic deformation errors, which are inevitable for the downhole robot actuator, and the results of which would affect the load distribution and fatigue life of the PRSM-aided actuator. To assist the complex task, in this study the mechanical behavior analyses of PRSM for the downhole robot system are investigated by considering axial loads, torque elastic deformation errors, and radial loads. Moreover, the calculation models for contact load distribution and fatigue life are established by utilizing the equivalent contact load and Hertz contact theory. Two cases for the robot actuator in the downhole environment are addressed, the results of which indicate that the contact load change and decrease with the thread growth direction of the PRSM, the first several threads bore most of the loads, and the last several threads only took a few loads. Additionally, the fatigue life reduces sharply under the condition that the axial loads, radial loads, and rotation speeds increase. Compared with the other two effectors, the fatigue life is more sensitive to the radial loads. The results show the sustainability of the presented screw–roller–nut and provide a potential reference for the downhole robot actuator motion analyses. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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14 pages, 2316 KiB

Open AccessArticle

Research on Pore Pressure Detection While Drilling Based on Mechanical Specific Energy

by Hu Yin, Hongwei Cui and Jiajia Gao

Processes 2022, 10(8), 1481; https://doi.org/10.3390/pr10081481 - 28 Jul 2022

Cited by 5 | Viewed by 3311

Abstract

The detection of the formation of pore pressure while drilling is of great importance to ensure safe drilling operations. At present, the dc-exponent concept is mainly used to detect pore pressure while drilling. The dc-exponent concept is based on the theory of shale [...] Read more.

The detection of the formation of pore pressure while drilling is of great importance to ensure safe drilling operations. At present, the dc-exponent concept is mainly used to detect pore pressure while drilling. The dc-exponent concept is based on the theory of shale compaction, which is limited when used in carbonate rocks. A mechanical specific energy (MSE)-based method is proposed to detect pore pressure in deep, complex intervals. The method is based on the theory that the energy consumed by the bit to break and remove a unit volume of rock can reflect the effective stress and pore pressure of the rock in situ. In this paper, a torque and weight on bit (WOB) transfer model is proposed for estimating the downhole torque and WOB using drill string mechanics. Meanwhile, the rotary speed and torque of the positive displacement motors under compound drilling are considered, and the model of total MSE under compound drilling is modified. The MSE-based method was used to estimate the pore pressure in a region in western Sichuan, and there is a good agreement between the detected and measured pore pressure. The results demonstrate that the accurate computed MSE-based method is useful in detecting pore pressure in deep complex intervals. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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9 pages, 4478 KiB

Open AccessArticle

Calculation Model of the Effect of Periodic Change of Normal Force on Sliding Friction Characteristics between the Planes

by Yongwang Liu, Yanan Liu, Zhichuan Guan and Yixiang Niu

Processes 2022, 10(6), 1138; https://doi.org/10.3390/pr10061138 - 6 Jun 2022

Viewed by 1601

Abstract

How to reduce the friction resistance between two planes is a difficult problem that has been studied in the field of tribology. Aiming at this problem, the concept of reducing the friction resistance by exciting the periodic change of normal force between the [...] Read more.

How to reduce the friction resistance between two planes is a difficult problem that has been studied in the field of tribology. Aiming at this problem, the concept of reducing the friction resistance by exciting the periodic change of normal force between the planes is proposed. A calculation model of the displacement amplitude distribution of the plate is established based on the principle of reciprocity of work, and the influence of the periodic change of normal force on sliding friction between the planes is studied. Additionally, an experimental device for analysis of friction between the planes under the periodic change of normal force is established. The calculation model of the plate’s displacement amplitude distribution considering the change frequency of normal force is verified and modified by experiments. The research results mainly show two aspects. On the one hand, the calculation model of the displacement amplitude distribution of the plate is in good agreement with the experimental results, which can effectively help to study the effect of periodic change of normal force on sliding friction between the planes. On the other hand, the change of amplitude and frequency of the normal force have an influence on the sliding friction between the planes. That is, the latter decreases with the increase of the former. The above conclusions have great reference significance for the study of vibration drag reduction in engineering production. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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21 pages, 15630 KiB

Open AccessArticle

Warning Signs of High-Pressure Formations of Abnormal Contour Pressures When Drilling for Oil and Natural Gas

by Tomas Huszar, Gabriel Wittenberger and Erika Skvarekova

Processes 2022, 10(6), 1106; https://doi.org/10.3390/pr10061106 - 1 Jun 2022

Cited by 4 | Viewed by 3828

Abstract

When drilling to obtain hydrocarbons (oil and natural gas), we cannot underestimate the anomalously high pressures in the deposit layers, as these pressures can cause an uncontrollable eruption. Therefore, it is important to look for signs of anomalous high contour pressures over time, [...] Read more.

When drilling to obtain hydrocarbons (oil and natural gas), we cannot underestimate the anomalously high pressures in the deposit layers, as these pressures can cause an uncontrollable eruption. Therefore, it is important to look for signs of anomalous high contour pressures over time, which, according to a detailed analysis, could be used to predict and quantify high formation pressures. These arise under conditions of intense vertical migration of formation fluids, where the liquids in the well have to carry part of the weight of overlying rocks and are often also related to tectonic activity. The main aim of the present study was to detect the emergence of a gas kick, which, as a result of an improper technological procedure, can cause an uncontrollable eruption, which can lead to a total accident of the well. In this article, we describe the use of modern drilling technology and sophisticated software that displays the current status inside the well. These can reveal impending pressure anomalies that can cause complications in managing the gas kick in oil and natural gas drilling. We analysed the most appropriate procedure for well control in a hydrocarbon well using the “driller’s method” and the “wait and weight method”. On the basis of theoretical background, we verified the correctness of the procedure for well control and compared it with the reaction to gas kick from a well drilled in Hungary. In the article, we highlight mistakes, as well as the particular importance of properly managing gas kick and its early prediction. Proper management of gas kick and its early prediction highlight the particular importance of implementing safe and effective procedures in well drilling. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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24 pages, 3105 KiB

Open AccessArticle

Theoretical Analysis of the Micro Annulus of an Oil-Well Cement Sheath Formed via Cooling under Acid-Fracturing Conditions

by Donghua Su, Xuning Wu, Zaoyuan Li, Sheng Huang, Jin Li, Jinfei Sun and Guanyi Zheng

Processes 2022, 10(5), 966; https://doi.org/10.3390/pr10050966 - 11 May 2022

Cited by 10 | Viewed by 2559

Abstract

The plastic deformation and interface micro annulus of oil-well cement during acid fracturing are key reasons for the failure of the wellbore seal and sustained casing pressure. However, most of the existing research ignores the influence of the wellbore cooling effect during acid [...] Read more.

The plastic deformation and interface micro annulus of oil-well cement during acid fracturing are key reasons for the failure of the wellbore seal and sustained casing pressure. However, most of the existing research ignores the influence of the wellbore cooling effect during acid fracturing, owing to which, the design conditions in the theoretical analysis may be inconsistent with those of the actual wellbore, and the calculation results may be biased. In this study, a novel elastoplastic mechanical model of the cement sheath was established. This model can analyze the yield state of the cement sheath under the influence of three-dimensional principal stress and consider the effect of the differential temperature stress on the interface debonding of the cement sheath from the beginning to the end of acid fracturing. Moreover, the generation mechanism and development law of the interface micro annulus were clarified. The findings indicated that the influence of the intermediate principal stress cannot be ignored; otherwise, the elastoplastic analysis results of the cement sheath may be conservative. During acid fracturing, the casing–cement sheath interface is influenced by the differential temperature stress, and the interface is debonded; however, a micro annulus is not generated. The debonding of the cement sheath–formation interface and micro annulus occurs only when the cement sheath is completely plastic. After acid fracturing, the interface micro annulus is likely to be generated at the casing–cement sheath interface, and the presence of the differential temperature stress may increase the formation risk of the interface micro annulus. The research results can provide theoretical guidance for the prediction of oil-well cement sheath interface seals under acid-fracturing conditions. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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15 pages, 1163 KiB

Open AccessArticle

Rapid Site Selection of Shale Gas Multi-Well Pad Drilling Based on Digital Elevation Model

by Jijun Zhang, Nan Hu and Wenjing Li

Processes 2022, 10(5), 854; https://doi.org/10.3390/pr10050854 - 26 Apr 2022

Cited by 4 | Viewed by 2479

Abstract

Drilling and completion platform construction is a fundamental part of oil and gas reservoir development, and the location of construction directly affects the whole process of shale gas drilling and development. Due to the complex surface conditions and fragile ecological environment in mountainous [...] Read more.

Drilling and completion platform construction is a fundamental part of oil and gas reservoir development, and the location of construction directly affects the whole process of shale gas drilling and development. Due to the complex surface conditions and fragile ecological environment in mountainous areas, having an appropriate platform location can significantly reduce shale gas development and environmental costs. The DEM (digital elevation model) includes geographic elevation, surface complexity, land use type, and other data, so it can be used for rapid site selection for shale gas multi-well pad drilling. In this study, first, research results related to drilling platform site selection were analyzed and summarized, and then a platform site selection method aiming to minimize the total well construction cost was developed. Second, the well construction costs were decomposed into the surface construction costs and the underground construction costs, and the site selection model with the lowest total multi-well pad construction costs was established. Third, ground feature data obtained from DEM (digital elevation model) processing were substituted into the site selection model and solved using the genetic clustering algorithm. Finally, two practical cases were used to verify the research method developed in this study. The results show that the platform site selection results can be used to not only guide the formulation of development plans, but also to reduce the scope of the field investigation in the process of site selection, reduce the intensity of field work, and improve the work efficiency. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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11 pages, 2593 KiB

Open AccessArticle

A New Method for Measuring Water Holdup of Oil-Water Two-Phase Flow in Horizontal Wells

by Yanjun Wang, Jianlong Han, Zhiqiang Hao, Lijian Zhou, Xinjie Wang and Mingwei Shao

Processes 2022, 10(5), 848; https://doi.org/10.3390/pr10050848 - 25 Apr 2022

Cited by 2 | Viewed by 2046

Abstract

The production profile logging technology of Oil-water two-phase flow is an important support technology for efficient development of horizontal oil wells. Moreover, the water holdup of Oil-water two-phase flow is one of the important dynamic measurement parameters for production profile logging technology. Flow [...] Read more.

The production profile logging technology of Oil-water two-phase flow is an important support technology for efficient development of horizontal oil wells. Moreover, the water holdup of Oil-water two-phase flow is one of the important dynamic measurement parameters for production profile logging technology. Flow patterns in horizontal oil wells are more complex than those in vertical oil wells, making water holdup measurements more difficult. In China, horizontal oil wells are characterized by low liquid production, high water cut and layered development; hence, the concentrating flow logging scheme is adopted to reduce the effects of flow patterns on measurement. In this paper, we proposed a new method of measuring water holdup of Oil-water two-phase flow for the production profile logging in horizontal oil wells. Firstly, the structure of water holdup sensors and the measuring principle of water holdup were introduced. Secondly, the dynamic test research was carried out on the horizontal well simulation facility by using the test prototype of the water holdup measurement method of Oil-water two-phase flow. Additionally, the response characteristics of water holdup sensors at five inclined angles were emphatically discussed. Finally, the measurement error of water holdup was calculated and evaluated in detail. Experimental results show that the absolute values of measurement error of water holdup are less than 5% while the total flow rate ranged from 10 m³/d to 200 m³/d, and the water cut ranged from 30% to 90%, respectively. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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43 pages, 8873 KiB

Open AccessArticle

Application of a Deep Learning Network for Joint Prediction of Associated Fluid Production in Unconventional Hydrocarbon Development

by Derek Vikara and Vikas Khanna

Processes 2022, 10(4), 740; https://doi.org/10.3390/pr10040740 - 11 Apr 2022

Cited by 4 | Viewed by 5716

Abstract

Machine learning (ML) approaches have risen in popularity for use in many oil and gas (O&G) applications. Time series-based predictive forecasting of hydrocarbon production using deep learning ML strategies that can generalize temporal or sequence-based information within data is fast gaining traction. The [...] Read more.

Machine learning (ML) approaches have risen in popularity for use in many oil and gas (O&G) applications. Time series-based predictive forecasting of hydrocarbon production using deep learning ML strategies that can generalize temporal or sequence-based information within data is fast gaining traction. The recent emphasis on hydrocarbon production provides opportunities to explore the use of deep learning ML to other facets of O&G development where dynamic, temporal dependencies exist and that also hold implications to production forecasting. This study proposes a combination of supervised and unsupervised ML approaches as part of a framework for the joint prediction of produced water and natural gas volumes associated with oil production from unconventional reservoirs in a time series fashion. The study focuses on the pay zones within the Spraberry and Wolfcamp Formations of the Midland Basin in the U.S. The joint prediction model is based on a deep neural network architecture leveraging long short-term memory (LSTM) layers. Our model has the capability to both reproduce and forecast produced water and natural gas volumes for wells at monthly resolution and has demonstrated 91 percent joint prediction accuracy to held out testing data with little disparity noted in prediction performance between the training and test datasets. Additionally, model predictions replicate water and gas production profiles to wells in the test dataset, even for circumstances that include irregularities in production trends. We apply the model in tandem with an Arps decline model to generate cumulative first and five-year estimates for oil, gas, and water production outlooks at the well and basin-levels. Production outlook totals are influenced by well completion, decline curve, and spatial and reservoir attributes. These types of model-derived outlooks can aid operators in formulating management or remedial solutions for the volumes of fluids expected from unconventional O&G development. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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12 pages, 11541 KiB

Open AccessArticle

The Application of Breakthrough Pressure in the Evaluation of the Sealing Ability of Cement–Casing Interface and Cement Matrix in Underground Gas-Storage Wells

by Yan Yang, Lukuan Li, Wenyan Yu, Yan Zhou, Kuanliang Zhu and Bin Yuan

Processes 2022, 10(4), 620; https://doi.org/10.3390/pr10040620 - 22 Mar 2022

Cited by 2 | Viewed by 2303

Abstract

This paper proposes an evaluation system for the sealing ability of cement–casing interface and cement matrix, which was developed based on a permeability testing device and a model that predicts the breakthrough pressure of cement sheath matrix and interfacial transition zone (ITZ [...] Read more.

This paper proposes an evaluation system for the sealing ability of cement–casing interface and cement matrix, which was developed based on a permeability testing device and a model that predicts the breakthrough pressure of cement sheath matrix and interfacial transition zone (ITZ). It was found that the breakthrough pressure of ITZ was much smaller than that of cement matrix. Moreover, compared with water-based drilling fluid, oil-based one led to lower breakthrough pressure of ITZ even after the flushing treatment. Meanwhile, latex, resin and elastic materials enabled a substantial rise in the breakthrough pressure of cement matrix. However, compared with the latex, resin and elastic cement, the expansive cement had higher breakthrough pressure of ITZ, indicating an improvement on the interface sealing ability. Additionally, a small enlargement rate of the hole diameter and long effective bond were able to prevent gas storage wells from leakage. Full article

(This article belongs to the Special Issue Oil and Gas Well Engineering Measurement and Control)

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