bluuebunny/crossref_metadata_2025 huggingface dataset:
Data Driven Shear Wave Velocity Prediction in a Carbonate Reservoir Using Conventional Well Logs
Authors: Esmaeilpour S. , Ispas I.
Published: September 2023

Geomechanical characteristics such as Young's modulus, Poisson's ratio, and Lamé parameters may be estimated using a combination of compressive and shear velocities. The static characteristics of formations and in-situ stresses may be estimated using these parameters. Sonic logs aren't typically available, especially for older wellbores. Additionally, on several occasions where the sonic logs have been made accessible, they are usually P-waves, and shear wave velocities are not present. Unfortunately, because of the significant expense associated with this log, it is not extensively utilized. Obtaining the shear wave velocity of rocks in a more efficient and cost-effective manner is necessary. Since well logs are vital in the reservoir characterization and development process, methods for approximating missing log information are essential. According to the literature, there is no specific straightforward correlation that could be utilized to accurately determine shear wave travel times based on well log data. The primary objective of this study is to predict shear wave velocity logs from conventional wire-line logs at the Wellington oil field in south central Kansas. This leads to the study's main idea. This research focuses on establishing a meaningful correlation between conventional logs and shear wave velocity in a cost-effective manner utilizing various approaches and data mining. The Wellington oil field, located in south central Kansas, is the subject of this research. Empirical correlations, linear regression, and neural networks were used initially to predict shear wave velocity. Ultimately, the data-driven model developed using standard well logs accurately predicts shear wave velocity in the Wellington oil field, demonstrating its reliability and effectiveness. Therefore, while direct measurement of shear wave sonic velocities is preferable, derived values can still provide useful insights when direct measurements are not possible or practical.

INTRODUCTION

Characterizing variations in petrophysical parameters over an oil and gas field's sedimentary interval is essential to its development (Archie, 1950). Consequently, laboratory measurements on core plugs, analysis of petrophysical well logs, and seismic inversion all contribute to the development of valuable estimations of reservoir physical parameters. The optimum way for determining uncertainty in predictions is to combine these several approaches, which have direct consequences for risk control in drilling operations (Pennington, 2001).
Blue Hydrogen Production from Oil Using Partial Oxidation and Aquathermolysis
Authors: Fakher Sherif , Tamer Sara , Eltohamy Mohamed , Abdelaty Bassel , Ali Maryam
Published: September 2023

Hydrogen is currently viewed as an extremely promising future source of energy that is both energy dense and environmentally friendly. One of the main issues with hydrogen is its production, which is extremely costly and thus results in a higher energy input than output. This research proposes a new method for hydrogen production using oil to reduce the reliance on freshwater and reduce the overall cost of the hydrogen generation. The research reviews all the conventional processes of producing blue hydrogen using natural gas, and studies the applicability of using oil as the feedstock instead of gas. The research then introduces a novel experimental setup to study hydrogen production from oil and highlights the advantages and limitations of the process. Finally, the research investigates the utilization of ash as a catalyst for blue hydrogen production from oil. This research can help increase the production of blue hydrogen by increasing the sources that can be used for blue hydrogen production. It also helps highlight the advantages and limitations of blue hydrogen production from oil and the main industrial methods that can be used for this application based on existing hydrogen production plants.

INTRODUCTION

Hydrogen is considered one of the main energy contributors of the future. It is usually produced from a hydrogen rich compound, mainly hydrocarbons or water (Fakher, S. et al., 2020; 2021; 2022). Due to the vast number of hydrogen production methods, hydrogen is usually classified as a color based on its source, process used to produce it, and if any greenhouse gas emissions are associated with its production (Fakher, S. and Fakher, A., 2021). Figure 1 shows all the common hydrogen colors, their source, and the main processes used to produce them (Fakher, S., 2020). As shown in Figure 1, several hydrogen colors are associated with fossil fuels. In order for the hydrogen to be classified as blue, it must originate from a hydrocarbon and have no emissions. This is achieved by coupling the process of hydrogen production with a carbon capture technology (Fakher, S. and Khlaifat, A., 2022).
An Adaptative Well Trajectory Control Method for Drilling Automation
Authors: Junlong Chen , Xueping Tang , Xinmiao Teng , Wenkai Gao
Published: September 2023

It is necessary to take some activities to correct the well-trajectory when it deviated from the designed well-path for the complex structural wells. In order to reduce the deviation from the planned well-path, we proposed a path following algorithm by backstepping method. The relative distance between the bit and planned well-path was calculated by the true vertical depth (TVD). The first and second order differential equations of the offset were established as the control function. Lyapunov function was constructed not only to verify the global consistent asymptotic stability of the system but also form a build-up rate control method. When the deviation between the real drilling trajectory and the planned well-path has exceeded the allowable threshold value, the algorithm automatically calculates the relative distance and angle, analyses and send the optimal strategy to the steering tools. The results show that the above algorithm can quickly track the designed well-path and ensure to avoiding oscillation. This method can be used in the future downhole closed-loop system.

INTRODUCTION

Downhole closed-loop steering drilling technology primarily employs automatic control systems to achieve dynamic adjustment of wellbore trajectory through real-time monitoring and analysis of borehole trajectory, and to ultimately achieve targeted drilling along the optimal borehole trajectory. After the downhole data is transmitted to the ground in real time, the ground system will dynamically analyse the downhole working conditions, send control instructions to the downhole executive mechanism, and form closed-loop control through two-way transmission of information in order to achieve real-time optimisation of drilling parameters and significantly increase drilling speed and reservoir drilling rate. The design of the downhole closed-loop control is predicated on the mechanical analysis and structure of the drilling instruments. The controller outputs the target curvature results by inputting the current position data (measured depth, inclination, and azimuth), the position and attitude of the target point, and the utmost dogleg that the drilling instrument is capable of achieving. The result of the controller is transmitted to the steering tools, and the interior structures of the bottom hole assembly (BHA) adapt to accommodate the new drilling trajectory.
Formation Evaluation Using in Situ Penetration Testing and Simulation Data
Authors: Shen Xinpu , Fehr Cory
Published: September 2023

Values of uniaxial compressive strength (UCS) and tensile strength (TS) are two key rock properties which determine the mechanical response of rock under penetration loading. Penetration testing is a popular means for obtaining values of UCS and TS of rock. A novel method has been developed for rock formation parameter identification with in situ penetration testing data obtained in the in situ, intact state. The workflow includes two parts: 1) developing a set of numerical models for simulating the rock penetration process within the in-situ environment. These models include the penetration cone and the rock to be penetrated. Continuum Damage Mechanics (CDM) is used for simulating the fracturing process of rock during penetration. Frictional contact is assigned to the cone-rock interaction. 2) developing a regularized least squares method for parameter identification with the measured data from the in-situ penetration test. A sensitivity matrix is derived for identification of values of UCS and TS of the rock being penetrated. Methodology validation was completed through parameter identification of UCS and TS of a concrete barrel. The values of UCS and TS of the concrete were obtained with a set of lab tests which are conventional processes for UCS and TS measurement. With a given displacement loading of the penetration cone, the 3D numerical model simulated the penetration process. By using the least squares method, a numerical solution of parameter identification for UCS and TS is obtained with a given accuracy tolerance. Contours of damage variables during penetration are presented along with the curves of penetration force vs time. These numerical resultant values of UCS and TS are consistent with the values of UCS and TS obtained with conventional tests. In conclusion, the method was proven to be practical and reliable in identifying the values of UCS and TS with data obtained by the in-situ penetration test
Induced Mechanism of Stope Roof Rockbursts in Underground Excavation
Authors: Deng J. , Wang X. Q.
Published: September 2023

A rockburst is defined as a sudden and violent disruption of rock in underground excavation. Rockbursts have been regarded as the least understood and the most feared mining disasters. Excavation-induced stress redistribution may lead to slippage of some pre-existing faults or even a new faulting in the near field of an underground opening. Both fault slippage and faulting generate seismic waves that propagate from the hypocenter outward in the rock mass. It was observed that rockbursts are induced by a seismic event when the seismic waves arrive at the free surface of the underground opening. This paper is aimed to study the mechanism of stope roof rockbursts induced by seismic waves using the dynamic buckling theory. The roof is regarded as a beam on elastic foundations under axial seismic waves. The seismic wave is modelled as an excitation with multiple frequencies. A new numerical algorithm is proposed to construct rockburst (instability) diagrams. Our study shows that the amplitude and frequency of the seismic wave play a critical role in the occurrence of roof rockbursts in terms of the mechanisms of perturbation effect and parametric resonance. Based on the mechanism analysis, insights are provided to alleviate the hazard of roof rockbursts.

INTRODUCTION

In Ontario, Canada, more and more underground mines are operating at depths approximately 3000 meters. With the increase of mining depth, underground mines are generally more prone to ground instability incidents. In underground mines in Ontario, ground instability has been one of the main claims of fatalities. According to statistics, nearly 50 workers were critically injured, and 10 workers died due to rock falls of ground or rockbursts in underground mines in Ontario between 2000 and 2019.

A rockburst is defined as a sudden and violent disruption of rock or disturbances of roof or walls in underground excavation, which is caused by or accompanied by a "shock" or tremor (seismic event) of sufficient magnitude, to cause obvious damage to support and excavations, or widespread simultaneous fall of rock. Rockbursts can be classified in terms of the source mechanism and the damage mechanism (Durrheim 1999).
Predicting Ground Surface Deformation Induced by Pressurized Fractures Using Conditional Generative Adversarial Networks
Authors: Salimzadeh S. , Kasperczyk D. , Kadeethum T.
Published: September 2023

Hydraulic fracturing has been widely applied in subsurface to facilitate hydrocarbon flow or as a preconditioning method to promote normal caving behavior in mining operations. The success of the method prominently relies on the geometry of the induced fractures in the host rock. An array of high-resolution tiltmeters is commonly used to measure the displacement gradient (tilt angle) of ground surface during hydraulic fracturing operation, and to infer the geometry of the induced fractures. In this work, we present a machine-learned model that is capable of predicting the surface tilt resulting from a pressurized fracture, using Conditional Generative Adversarial Networks (cGAN). Fracture apertures along horizontal and vertical planes are given as input while surface tilt vectors are provided as output for the forward model. A 3D finite element model with discrete fractures is utilized as the Full Order Model (FOM) to create training data. The fractures are pressurized uniformly to induce a displacement at the ground surface. Images of the fracture aperture in XY and XZ planes, and surface tilt vector components (tilt X and tilt Y) are used for the training process. Three different loss functions are used, and the predicted tilts are compared to the real (FOM) tilts. The results show that the trained cGAN with Wasserstein loss and gradient penalty (W-model) can predict the ground surface tilt due to the pressurized fractures at variable dip angles.

INTRODUCTION

Hydraulic fracturing has been frequently applied as a preconditioning method to promote normal caving behavior in mining operations. The success of the method prominently relies on the geometry of the induced fractures in the stiff overburden layer. An array of high-resolution tiltmeters is commonly used to measure the displacement gradient (tilt angle) of ground surface during hydraulic fracturing operation, and to infer the geometry of the induced fractures or pressure plumes using simplified models (Lecampion et al., 2005; Salimzadeh et al., 2022).
Preparation and Characterization of a Novel Magnetic High-Titanium Lunar Regolith Simulant for Geotechnical Engineering Application
Authors: Ningxi Zhou , Jian Chen
Published: September 2023

The moon exploration has progressed to the phase of in-situ resource utilization. It is critical to comprehend the unique mechanical response and engineering properties of lunar regolith for successful exploration. Currently, most experimental studies on the mechanical properties of lunar regolith have been conducted on Earth, ignoring the effects of the low-gravity environment of the lunar surface. The geomechanical magnetic model test can simulate the lunar surface's low-gravity environment more accurately using magnetic fields. However, current lunar regolith simulants lack magnetism and cannot meet the requirements of magnetic model tests. To address this, a high-titanium lunar regolith simulant with certain magnetism called IRSM-1 is developed using volcanic ash and titanomagnetite. The new simulant's properties are evaluated, including composition, particle distribution and morphology, magnetic properties, shear strength, and compressibility. The results are compared with published data for lunar regolith samples and widely used simulants. The IRSM-1 simulant is found to have similar composition and geotechnical properties to real lunar regolith. Additionally, the simulant possesses sufficient magnetism to meet the requirements of magnetic model tests. In conclusion, the high-titanium magnetic IRSM-1 simulant displays considerable potential for use in geotechnical engineering applications and may prove instrumental in supporting successful lunar exploration missions.

INTRODUCTION

Since the start of the 21st century, the strategic significance of the Moon in economic, military, and scientific research has increasingly become more prominent. Humanity is experiencing a renaissance of lunar exploration. The exploration of the Moon and the exploitation of its resources have garnered attention from leading space research institutions worldwide. In 2019, NASA proposed the "Artemis" project, with the aim of establishing a lunar base in 2028. Likewise, in 2021, China and Russia jointly launched the "International Lunar Research Station Roadmap" and the "International Lunar Research Station Partner Guide", officially commencing the International Lunar Research Station (ILRS) project. Additionally, Japan, India, Israel, and various other countries and organizations have joined the ranks of lunar exploration. The Moon has emerged as a new focus of space strategies for multiple countries (Pei et al., 2020).
PDC Bit Wear Condition Judgment Based on Object Detection and Computer Vision
Authors: Yang Donghan , Song Xianzhi , Liu Donglei , Guan Zirui , Pan Tao , Zhu Lin , Zhu Zhaopeng
Published: September 2023

In recent years, due to the remarkable advantage of increasing speed and reducing cost, PDC bits has occupied a dominant position in the drilling bits market, becoming the important drilling tools in the petroleum markets. In the drilling process, the bit will wear itself when breaking formation. The abrasion condition of the bit can be divided into two kinds: one is the normal wear, the cutter and rock produce continuous or intermittent friction to break the rock. The process of the friction between the cutter and the rock produces micro-cutting, scratching, rubbing and so on to make the bit wear and blunt. The other kind of wear is abnormal wear, such as tooth collapse, chip drop, polycrystalline diamond layer falls off. The drilling period and drilling costs are affected by the abrasion of the drilling bits, which can lead to reduce the rock breaking efficiency and slower ROP. Therefore, it is necessary to replace the bit in time to ensure the rate of penetration. So, accurate determination of the PDC bit abrasion is very important to achieve safe and efficient drilling. At present the evaluation of bit condition mainly relies on manual and experience to carry out the wear rating of the drilling bit, which is subjective. To evaluate the state of drill bit more accurately, this experiment uses the computer vision and object detection algorithm to judge the condition of drill bit through the image of the bit.

BACKGROUND

Nowadays, roller cone bits and PDC bits are the most commonly used bits in the field of oil drilling. With the continuous improvement of PDC bit cutter technology, PDC bit has become an important tool in petroleum market. Compared with traditional roller cone bits, PDC bits offer significant advantages in cost, rate of penetration and footage per bit when drilling, especially in deep and high-pressure wells.[1] Although PDC bits has high wear resistance, it is inevitable that the PDC bits being worn out. If the bit abrasion reaches a certain degree, the drilling efficiency of the bit will be significantly reduced. Therefore, it is necessary to judge the wear condition of drilling bit accurately and efficiently to realize the safe and efficient drilling.[2]
Impact of Discontinuities with Slip-Weakening Friction on the Structural Deformation of a High-Speed Railway Tunnel inJointed Stratified Rock Masses Under Cyclic Train Loadings
Authors: Zhang Z. X. , Pan W. B. , Wang S. F. , Lei Q. H.
Published: September 2023

It is crucial to assess the performance of a high-speed railway tunnel under dynamic train loading since structural deformations may lead to safety-relevant issues, such as train derailment or rollover. The structural deformation of a high-speed railway tunnel results from the train loading-induced response and interaction of tunnel structures and surrounding rock masses. Our research investigates the slippage behavior of discontinuities with slip-weakening friction around a tunnel under dynamic train loadings, and further analyzes their impacts on structural deformations. A distinct element method-based commercial software (UDEC) is used to build a 2D circular tunnel situated in jointed stratified rock masses. We compare the modeling results by the Coulomb slip model and slip-weakening model, and further conduct parametric studies about the bedding plane dip angle, joint length/spacing, and critical slip distance. We report that discontinuities with slip-weakening friction are more prone to be reactivated and ruptured under dynamic train loadings, and the resultant shear displacements of discontinuities associated with rock block deformations and movements would further induce significant structural deformations. Our simulation results have important implications for assessing the performance of a high-speed railway tunnel as well as the safety of train operations.

INTRODUCTION

The rapid development of high-speed railways in China, e.g., the planned Sichuan-Tibet railway line, imposes an increased demand of tunnel construction (Li et al. 2016). Due to the high performance requirements of high-speed train operation, the structural deformation of a tunnel should be carefully examined and controlled to ensure the safety and smoothness of train tracks (Fu et al. 2022; Qian et al. 2019). Some considerable structural deformations have been observed under dynamic train loadings (Wang et al. 2022), as a result of the interaction of tunnel structures and surrounding rock masses (Wang et al. 2020). Discontinuities are widely present in rock masses like stratified sedimentary formations, a typical lithology through which parts of the Sichuan-Tibet railway pass (Chen et al. 2019; Guo et al. 2020). It is expected that the potential shear slippage of these discontinuities under dynamic train loadings could play an important role in structural deformations.
Evaluation of Non-Destructive Stress Measurement Methods for Investigating Stress Memory in Rocks
Authors: Ali Z. , Karakus M. , Nguyen G. D. , Amrouch K.
Published: September 2023

Rock bursts and spalling are major concerns for the design of deep underground structures under high in-situ stress conditions. A full constrain of in-situ stress magnitude and spatial distribution is therefore essential for managing the occurrence and severity of such phenomena. In recent decades, non-destructive stress measurement methods have been developed as a reliable alternative to traditional methods. These methods are based on rock stress memory and rely on accurate measurements of strain and acoustic data during uniaxial cyclic loading of specimens. In this study, several non-destructive stress measurement methods based on strain measurement and acoustic emission were evaluated. Uniaxial cyclic loading and unloading tests were performed on cylindrical specimens of Hawkesbury sandstone, and the deformation was monitored using strain gauges, Linear Variable Differential Transformer (LVDTs), Digital Image Correlation (DIC) and high-speed acoustic emission (AE) system. The strength and capability of each method in determining the applied stresses were evaluated by analyzing the strain and acoustic data collected during uniaxial cyclic loading. Although all methods were found effective in determining the applied stresses, our results indicate that the DRA and SMM methods were more precise and consistent.

INTRODUCTION

The Kaiser effect is a phenomenon observed in rock specimens when a uniaxial cyclic loading is applied in a laboratory. Acoustic emission (AE) activity begins just after the applied stress exceeds the peak of previously applied maximum stress to the specimen (Lavrov, 2002). This memory of previously applied stresses is found not only as a change in AE activity but also in the strain rate of rock specimens under a constant loading rate, known as the stress memory (Yamamoto et al., 2009). Kuwahara et al. (1990) proposed a model for the inelastic deformation of rock specimens under axial loading of compression to explain the mechanism of the Kaiser effect. According to Kuwahara et al. (1990) there are many potential micro-cracks in a rock specimen, and the strength of the specimen depends on potential cracks and applied stress to the specimen. If the applied stress is increased to a certain magnitude, all the potential micro-cracks with strengths smaller than the applied stress should initiate or propagate (Hoek and Martin, 2014). When the specimen is subjected to stress again after unloading, new micro-fractures hardly occur at first, and the pre-existing crack produced in the previous loading steadily moves with an increase in applied stress until the applied stress reaches the peak of the previously applied stress. New micro-fractures begin to occur only after the applied stress has reached the previous stress.
Unconfined Compressive Strength Estimation in the Shale Gas Reservoir Using Data Driven Technique
Authors: Shi Xian , Yang Yuanyuan , Liao Yong , Wang Daobing , Han Songcai , Gao Qi
Published: September 2023

Identifying and predicting rock unconfined compressive strength is critical to well design, wellbore stability, and hydraulic fracturing stimulation in shales. However, accurate prediction of rock mechanical properties is hard in the absence of high-resolution advanced geophysical logs (e.g., image logs) and laboratory mechanical core samples. This study focuses on rock mechanical parameter estimation using three data-driven techniques: backpropagation (BP) network, support vector machine (SVM), and extreme learning machine (ELM) models in a shale gas reservoir. Additionally, this study aimed to obtain accurate rock mechanical properties, which have proven challenging using conventional petrophysical methods in wells without downhole core data. A total of 350 samples from 22 wells with laboratory measurement data were used to train and validate the neural network. Robust algorithms were used to provide fast and accurate prediction results, which were verified by comparing them with other approaches. The trained machine-learning models were cross-validated to check their robustness. The network model was then applied to estimate rock unconfined compressive strength for the remaining wells. The predicted results had a good match well with the laboratory test conclusions. Based on the estimations, rock mechanical properties were mapped and analyzed in the target shale gas zone. This method is helpful for geomechanical modeling in shale gas reservoirs.

INTRODUCTION

Uniaxial compressive strength is the ultimate ability of a rock specimen to resist damage under uniaxial pressure. When a rock is subjected to external forces, damage occurs when the stress reaches a certain limit value, which is the strength of the rock. As one of the most important mechanical indexes of rock, understanding the uniaxial compressive strength is necessary for hydraulic fracturing design and wellbore stability.

I To have a more accurate characterization of the reservoir geomechanical properties and the corresponding engineering parameters and to provide a basis for the later development of well pattern and stimulation scheme, well logging is generally used for the geomechanical properties prediction. However, due to the absence of several well logs and empirical parameters in the geomechanical modeling, accurate geomechanical properties estimation should be calibrated with laboratory experiments. However, in the absence of high-quality laboratory cores, it is challenging to accurately conduct experiments. Therefore, this study uses artificial intelligence techniques to predict uniaxial compressive strength by combining well logs and laboratory mechanical results.
Experimental Investigation of Fracture Initiation and Propagation Characteristics in Deep Coal Seams
Authors: Jian Wu , Libo Zhou , Qi An , Jianchuan Li , Fan Yang , Qi Yang , Yesong Li , Yao Jiang , Ben Li , Hui Li
Published: September 2023

Deep coal seams usually require hydraulic fracturing to enhance the coalbed methane productivity due to their low permeability and low porosity features. Identifying the initiation and propagation mechanics of deep coal seams could help to optimize the hydraulic fracturing design and operations and effectively stimulate the fracture network system in coalbed methane. This paper designed and conducted lab-scale hydraulic fracturing experiments to evaluate the effects of frac-fluid viscosity, water pump rate, and coal bed lithologies on fracture initiation and propagation. Totally 10 outcrop coal samples were collected and cut to 10cm × 10cm × 10cm for fracturing physical simulation. The in-situ stress (stress-difference) of the LinXing(LX) coalbed (2000m vertical depth, Shanxi China) was used as confining stress of the experimental samples. Stimulated fracture surface area calculated from computerized tomography (CT) scan and three-dimensional reconstruction was used as the primary indicator to analyze the significance of hydraulic fracturing operation parameters. Results showed that water pump rate, frac-fluid viscosity, and perforation angle were the three significant factors that could affect the complexity of the fracture network (fracture propagation). As the water pump rate increased from 3ml/min to 7ml/min, both fracturing pressure and loading time increased. The pump rate contributes to the complex fracture network. As the viscosity of the frac-fluid increased from 10mPa·s to 50mPa·s, the fracturing pressure increased, and the complexity of fractures reduced. Among mudstone, coal, and mud-coal samples, the fracturing pressure of mudstone is highest, than is mud-coal rock, while the fracturing pressure of the coal sample is lowest. Fracturing pressure increased with the perforation angle increase (90°>60°>30°>0°). The experimental results can provide fundamental data for the on-site deep coal seam fracturing design and optimization.

INTRODUCTION

Coalbed methane has been paid more and more attention in recent years (Cao et al., 2015; Li et al., 2017; Li et al., 2023). It is understood that the geological reserves of deep coalbed methane resources in China are about 22.45 trillion cubic meters, accounting for 61% of the total resources (Guo et al., 2015; Wang et al., 2022). As the unconventional oil and gas resource, the deep coal seam has poor physical properties, high stress, low permeability, and strong adsorption capacity, so the effect of conventional fracturing is not efficient (Qin and Shen, 2016; Yan et al., 2015; Chen et al., 2016; Li et al., 2018; Li, 2022).
Mechanical Characterization of Shale Minerals Based on Nanoindentation Technology
Authors: Li Lingdong , Liu Zhaoyang , Yu Wenhua , Lv Zehao , An Zhibo , Zhang Xiaoning , Duan Luyi
Published: September 2023

Traditional macro-mechanical parameter testing methods, such as single-triaxial rock mechanics experiments, have high requirements on the size and integrity of rock samples. The nanoindentation technique has been gradually applied to the testing of rock mechanical properties, which provides an effective tool to measure rock mechanical properties at the nanoscale. In this paper, the shale samples from the Jimsar and Bohai Bay basins were used to obtain the microscopic mechanical parameters of the shale by nanoindentation experiments, and the Weibull model was used to evaluate the mechanical parameters of the two regions. The results show that both groups of samples have strong inhomogeneity and rich microscopic pore structure, with a larger elastic modulus of 35.23 GPa in the Jimsar Basin and a smaller elastic modulus of 26.78 GPa in the Bohai Bay Basin. In addition, the simulation results show that different mineral compositions have a strong influence on the nanoindentation curves, resulting in displacement-load curves deviating from the classical power exponential form and showing diverse anomalous features.

INTRODUCTION

Shale oil and gas, as an important unconventional energy source, greatly improves the world's energy supply structure (Du et al., 2018).The mechanical properties of shale reservoirs are crucial for the efficient extraction of shale oil and gas (Li et al., 2018). However, as a special kind of soft rock, shale is easily fractured and muddied, making coring operations very difficult (Ge et al., 2015; Yang et al., 2016). Coupled with the gradual development of mineral resource extraction to deeper depths and complex geological and tectonic environments, this poses a major challenge to traditional indoor tests to obtain shale rock mechanics parameters.

In recent years, nanoindentation experiments for the study of microscopic damage and measurement of micromechanical parameters at the nanoscale have been further developed. Oliver and Pharr (2011) invented indentation experimental techniques based on load and displacement measurements, where material hardness and modulus of elasticity can be determined directly from the indentation load-displacement curve, eliminating the need for other imaging techniques to assist. Indentation experiments have received a lot of attention from scholars due to their simplicity, efficiency and nondestructive nature. Nanoindentation has become a simple method to describe the mechanical properties of shale.
Study on the Elasto Viscoplastic Constitutive Model of Shale Influence on Fracture Conductivity
Authors: Li Shiyuan , Zhao Jingya
Published: September 2023

Shale oil and gas reservoir is a new hotspot of oil and gas exploration and development. It is very important for fracturing production to produce artificial fractures with sufficient conductivity. Shale clay and organic matter content is high, which is easy to creep, and it makes the proppant embedded in the formation and affects the fracture conductivity.In this paper, an elasto-viscoplastic constitutive model is proposed to study the influence of shale creep on the conductivity. Isotropic linear elastic constitutive relation is adopted for elastic model, and the Perzyna model considering isotropic hardening is adopted for the viscoplastic model. Under the confining pressure of 5 MPa and the deviator stress of 10 MPa, 15 MPa and 20 MPa respectively, the triaxial compression creep experiments were carried out on the long 7 samples, and the material parameters in the viscoplastic model were determined by fitting the experimental data.The constitutive model is programmed into the user material subroutine UMAT of Abaqus using the return mapping algorithm. Then a triaxial compression numerical creep experimental model was established to verify the model. This model is applied to fracture conductivity model to study the influence of reservoir creep on the conductivity of artificial fractures and the sensitivity analysis of the influencing factors of fracture width was carried out.

INTRODUCTION

In the current context of "carbon peak" and "carbon neutral", the demand for natural gas as a clean and low-carbon fossil fuel is gradually increasing(Zhong et al., 2023). As an important source of natural gas, shale has attracted more and more attention(Katende et al., 2023). Hydraulic fracturing is the main means for developing of low-permeability oil fields such as shale (Maslowski & Labus, 2021). Whether to produce artificial fractures with sufficient conductivity is an important criterion for hydraulic fracturing evaluation(Lin et al., 2020).With the increase of closing pressure, the proppants at the fracture surface embed into the reservoir, and the embedded area is easy to block pores, rock crushing and shale flakes migrate, which hinders the flow of oil and gas(Zhang et al., 2014). In the porous media space composed of proppants, with the development of shale oil and gas, the proppant's effective stress increases, leading to the proppant being further embedded in the fracture surface.
Study of the Influence of Structural Parameters on the Output Characteristics of Torsional Impact Tools
Authors: Xin H. , Liu G. H. , Tian C. , Li J.
Published: September 2023

Torsional impact tools can effectively eliminate the stick-slip vibration of the drill bit, which can effectively increase the mechanical drilling speed. In this paper, a mathematical model of the motion of a torque-influenced tool is developed based on an analysis of the structure and working principle of the tool. The influence of structural parameters on the output characteristics of the tool was analyzed by taking the shock frequency and impact work as the evaluation criteria for the output characteristics of the tool. The results show that the motion of the pendulum and reversing value are non-linear at different stages. The impact frequency and impact power of the tool decrease with the increase of the nozzle diameter, increasing first and then decreasing with the increase of the gap between the pendulum and the outer casing, increasing with the increase of the drain hole area on the wall of the baffle and pendulum, and remain stable after reaching the peak and no longer increase. To obtain better output performance, the pendulum clearance and drain area of the tool have optimal values in the design of structural parameters. The research results have important reference significance for the design of torque impact tools.

INTRODUCTION

The PDC bit is prone to stick-slip vibration when drilling in hard strata, which seriously affects the mechanical drilling speed and bit life. Torsional impact tools produce high frequency, low amplitude impacts and are often used on the top of the drill to reduce or eliminate stick-slip vibration. Various structures of torsional impact tools have been designed. The field application practice shows that in order to achieve good drilling speed, different areas have different requirements for the impact power and frequency of the tools (Zhou et al, 2012). Scholars have conducted some research on the analysis of the kinematic characteristics of torsional impact tools and the calculation of output characteristics. Tian Jialin established a kinematic calculation model of torsional impact tools and analyzed the influence of inlet pressure and flow rate changes on the tool impact frequency (Tian et al, 2016). Wang Wei and established a kinematic mathematical model of impact tools and analyzed the nozzle size and displacement on the tool output characteristics. The effect of nozzle size and displacement on the output characteristics of the tool was analyzed (Wang et al, 2019).
Stress Variation Around the Balarud Lineament in the Zagros Fold and Thrust Belt and its Implication for Reservoir Geomechanics
Authors: Yaghoubi A. , Dusseault M. B. , Leonenko Y.
Published: September 2023

We investigate horizontal stress variation in the vicinity of the deep-seated Balarud Lineament in the northern part of Iran's Dezful Embayment in the Zagros Fold and Thrust Belt (ZFTB). Both petrophysical data from drilled oil and gas wells (3-4 km deep) and earthquake focal plane solutions (6 to 25 km deep) are used to constrain the orientation and relative magnitudes of the local and regional stresses. The stress orientations in the sedimentary rock strata and the basement are of two entirely distinct types. In the basement, constant regional NE-SW SHmax orientation is observed in the northern ZFTB. The seismologically determined local SHmax direction from 25 focal mechanisms around the Balarud Lineament is 29.3°±8.5°. However, observations of borehole breakouts and tensile-induced fractures indicate that the dominant SHmax orientation is N-S near the Balarud Lineament. The consistent stress direction in the basement indicates a high differential horizontal stress magnitude, whereas the principal stress orientation rotates 35° counter-clockwise in the sedimentary cover where the state of stress is extensional. The Lineament's second-order stress patterns are discussed in terms of wellbore placement and completion decisions.

INTRODUCTION

Anomalous relative stress magnitudes and orientations have been observed in the world's various uniform lithospheric stress fields. Stress deflection may be observed due to lateral density/strength contrasts, flexural stresses, or superimposed geological structures such as faults (Sonder, 1990) and salt diapirs (Dusseault et al., 2004). In the east-west-trending Transverse Ranges (California), the horizontal stress orientation is different by 25° from the reference stress state in the NW-SE San Andreas fault (Sonder, 1990). The regional NE-SW SHmax is reoriented to N-S in the area overlying the Peace River Arch in the Western Canadian Sedimentary Basin (Bell & McCallum, 1990). The same phenomenon is reported for the Amazon rift in central Brazil (Zoback & Richardson, 1996) and in the Swiss Alps and the northern Alpines foreland (Kastrup et al., 2004). Stress deflections can also be caused by reservoir depletion (Yale et al., 1994) and by earthquakes (Hauksson, 1994). Hauksson (1994) observed a 15° (±10°) rotation of local stress axes due to the 1992 Mw = 7.3 Landers's earthquake sequence. The scale at which second-order stress patterns occur depends on the degree of lateral density/strength contrasts and the size of geological structures and their orientation relative to regional stress fields (Sonder, 1990; Zoback, 1992).
Thermal Effect on Cement State of Stress in a Cement-Casing Structure
Authors: Meng M. , Frash L. P. , Carey J. W.
Published: September 2023

Temperature fluctuations within a wellbore are common occurrences in various applications, including carbon sequestration, hydrogen storage, and thermal storage. To ensure long-term well integrity, it is necessary to investigate the mechanical response of the cement annulus under thermal loading. In this study, we designed a two-layer cement casing structure to evaluate the stress state at the cement-casing interface under high pressure and high temperature conditions. We cured Class-G cement with a water-cement ratio of 0.4 and poured it inside the casing, subjecting it to 40 MPa and room temperature for seven days before elevating the temperature to 35, 45, 55, and 65°C. After correcting for casing thermal expansion, we found that the cement-casing interface stresses were 9.2, 11.1, 16.4, and 22.7 MPa under these temperatures, respectively. The corresponding coefficient of thermal expansion of the cement was 1.6 × 10−5 /°C. Throughout the experiment, there was no water exchange between the curing cement and the external reservoir. The cement pore pressure dropped to nearly zero after seven days of hydration, but it increased significantly with the elevated temperature and dissipated slowly. Additional tests are needed to correct for the pore pressure effect on the cement-casing interface state stress. Overall, this work contributes to a better understanding of cement's pore-mechanical behavior with thermal cycling under subsurface conditions.

INTRODUCTION

The global energy sector is shifting from fossil based systems to clean energy resources in response to the growing concern about climate change. The topics of carbon sequestration, hydrogen storage, and thermal storage become the target of the whole society. Despite this shift, wellbore remain the primary effective channel connecting subsurface space utilization and ground activities, making long-term well integrity crucial to ensure sustainable, reliable, and efficient energy storage and sequestration.

In a typical wellbore, cement annulus is usually the most vulnerable part, therefore, we care about cement's overall performance in maintaining zonal isolation, including rheological properties, chemical properties, and mechanical properties [1]. Usually, researchers propose new formulations with specific types of additives to improve displacement efficiency, reduce chemical shrinkage, and promote proper mechanical strength. Of all the aspects of performance, cement mechanical behavior directly determine the quality of zonal isolation throughout its functional life.
Decline Curve Analysis Using Machine Learning Algorithms: RNN, LSTM, and GRU
Authors: Vega-Ortiz Carlos , Panja Palash , Deo Milind , McPherson Brian
Published: September 2023

The traditional Arp's decline model failed to predict production from many oil and gas reservoirs due to some inherent assumptions like boundary-dominated flow contrary to long transient flow. Fundamentally, this is a time series curve fitting and forecasting problem. Advanced machine learning (ML) algorithms can be used to capture the unusual trend in hydrocarbon production decline. The objective of this study is to develop various ML algorithms such as Recurrent Neural Network (RNN), Long Short-Term Memory (LSTM), and Gated Recurrent Unit (GRU) in forecasting future production performance and estimating ultimate recovery (EUR).

Decline curve analysis (DCA) is a straightforward and rapid way to estimate future production simply by suitable curve fitting. However, the traditional Arp's method overestimates the production from many reservoirs, resulting in new empirical methods such as Power Law Exponential Analysis (PLE by Ilk, 2008), Logistic Growth Analysis (LGA by Clark 2011), and Duong Method (DM by Duong 2011). The outcomes of these recent models also depend on the quality of the data and the reservoir flow regimes. The machine learning algorithm is applied to overcome the drawbacks and limitations of the empirical decline curve models. Machine learning algorithms such as RNN, LSTM, and GRU are compared. The first 80% of time-series data is used for training the models and the last 20% is used for testing. The trained models are employed to forecast future rates and to calculate EUR. The value of NSE close to unity suggests good model performance. A normalized Nash-Sutcliffe model efficiency coefficient (NNSE) and Normalized Root Mean Squared Error (NRMSE) are selected for assessing the efficacy of different models. The LSTM models have several unique advantages over typical supervised machine learning algorithms. The models are flexible in handling multiple inputs in time series. The ML models developed in this work can be coupled with an economic model considering the future oil price and operational costs.

Machine learning is a research area quickly growing across several industries providing valuable insights. Machine algorithm for time series forecasting in the oil and gas industry has not been comprehensively explored. Results from this work will provide the literature with another application perspective with strong opportunities in production data analysis.