bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neural Networks Modeling of Shear Wave Velocity for Tight Gas Sandstone Formation
Authors: Yang Fan , Li Yesong , Yang Qi , Zhou Libo , Wu Jian , Mei Wenbo , Pu Shengxian , Feng Chun , Li Hui , Li Ben 
Published: September 2023

ABSTRACT
Shear wave velocity (Vs) is a key parameter in the calculation of rock elastic properties, such as Young's modulus, Poisson's ratio, shear modulus. However, due to technical and economic limitations, Vs is not always available (especially for older Wells). It is very important to predict Vs effectively and accurately. The characteristics of shear wave velocity prediction methods in different ultra-deep sandstone formations are compared, and an optimized neural network model is proposed. Training data is derived from real logging and logging interpretation results. The input parameters were determined according to the rock physical model, and the structure of the neural network (the number of hidden layers and the number of hidden neurons in each hidden layer), transfer function, training function and learning function are optimized according to the accuracy and training time. In order to solve the limitations of a single evaluation index on the evaluation of machine learning, a new evaluation index M4 of neural network was proposed in this paper. The accuracy of model predictions and sensitivity to outliers can be adequately evaluated. In addition, the interpretability analysis of the training model is carried out, and the results presented can be used to (1) estimate the S-wave velocity according to the above variables, and (2) evaluate the influence of each variable on the S-wave velocity.

INTRODUCTION
The unconventional resources from an ultradeep tight gas reservoir have received significant attention in recent decades (Li et al., 2021). Therefore, it is of great significance to conduct deep and ultra-deep gas resource exploration and development for expanding reserves, stabilizing production, and seeking new areas for exploration in old oil and gas fields (Li et al., 2019). In oil and gas field development engineering, parameters such as Young's modulus, Poisson's ratio, bulk modulus, and shear modulus are important elastic parameters that characterize rock properties and fluid information (Zhang et al., 2019). The cross-wave velocity in logging data is an important parameter for calculating and predicting reservoir rock physical parameters, reservoir identification, and pre-stack inversion.
Development of a Wellbore Stability Prediction Model Using Multiple Regression with Missing Core Samples: A Case Study of the Shunbei Oil and Gas Field
Authors: Chang Qifan , Fu Yun , Zhou Yitian , Zheng Lihui , Li Jie , Jin Yi 
Published: September 2023

ABSTRACT
The Shunbei oil and gas field, characterized by its intricate deep fault-karst reservoirs and fractured carbonate lithology, presents formidable challenges to wellbore stability during drilling and completion phases, precipitating adverse events such as wellbore collapse and fluid loss. This study embarks on addressing the paucity of data integral for effective wellbore stability prediction in this region, employing a tripartite methodological approach: identification of pertinent data and influential factors, enhancement of multiple regression accuracy, and selection of controlling factors. The study revealed that the multiple linear regression model delivered the most precise predictions for both the leakage rate and well diameter expansion rate. Crucial factors such as geodetic coordinates, drilling pressure, and azimuth were identified as exerting substantial influence on wellbore stability. By scrutinizing primary controlling factors and underscoring the crucial role of drilling pressure and displacement in averting collapse and leakage, this study provides invaluable insights applicable to actual production settings. This study, while enhancing understanding of wellbore stability through analyzing key factors, does not delve into quantitative control strategies. Nevertheless, it provides a practical framework for better management of wellbore collapse and leakage in Shunbei oil and gas field.

INTRODUCTION
Meeting the global energy demands requires exploration and development of oil and gas fields (Cui et al., 2023). However, drilling and completion of deep fault-karst reservoirs such as the Shunbei field (Baozeng et al., 2020) present significant challenges due to wellbore instability issues. These issues include wellbore collapse, fluid loss, and other prevailing problems (Lixin, 2020), which can lead to extensive equipment damage, increased drilling and operational costs, and endanger the safety of personnel.
The wellbore instability issues faced in the Shunbei field are primarily due to the fractured carbonate lithology, which exhibits fragility and poor mechanical properties (Yingtao et al., 2019). Precise prediction of wellbore instability and fluid loss in such formations is essential for efficient field development. The field of rock mechanics and wellbore stability has a long history, dating back to the early 20th century, when the first recorded studies focused on the stability of oil and gas wells (Cheatham, 1984).
Temperature Effects on Core Mechanics Testing – An Eagle Ford Case Study
Authors: Roberts Jon , Chapman Philip , Arrington Sean 
Published: September 2023

ABSTRACT
It has long been recognized that an important step in acquiring mechanical properties from core is to take the measurements at reservoir conditions. However, the actual test often only replicates the effective downhole stresses, while ignoring the elevated temperature downhole. To quantify the effects of temperature in the Eagle Ford Formation, a core testing program was designed to take advantage of having a large volume of similar rock provided by the HFTS 1 phase III horizontal core. This program involved 46 samples taken from ∼2.4 m of horizontal core. This ∼2.4 m of horizontal core represents ∼0.3 m of vertical section inside the Lower Eagle Ford Member. Multiple tests were performed on the core including anisotropy parameters, static and dynamic triaxial testing, pore volume compressibility and tensile strength. Some of the notable results include that the majority of samples showed an increase in tensile strength with temperature, a decrease in shear velocity at temperature, and an increase in Biot coefficient with temperature.

PROJECT INTRODUCTION
The Zgabay A 14H is the monitoring well associated with the HFTS 1 Phase III refracturing study in the Eagle Ford trend. As part of this study, a horizontal core was taken with the primary objective of understanding hydraulic fracture intensity and behavior in the far field. Geomechanical core testing was one component of the core analysis program designed to help understand and model hydraulic fracture growth.
Recent studies by industry and internal testing have shown there is a change in mechanical properties with temperature (Mitra, 2022) However, we had not investigated the effect of temperature on the Eagle Ford Formation. Therefore, with the relatively large volume of rock available in a similar facies provided when taking a horizontal core, we decided to use this unique opportunity to test the effect of temperature, in situ vs. ambient, on core testing results.
Pouring and Calibration of Hydrate-Bearing Sediment Substitutes
Authors: Hui Chengyu , Zhang Yiqun , An Youkeren , Wu Xiaoya , Huang Haochen , Li Gensheng 
Published: September 2023

ABSTRACT
As a potential pollution-free energy with wide distribution and huge reserves, the effective development and utilization of natural gas hydrate is of great significance to alleviate the shortage of resources and realize sustainable development. Improving the mining efficiency is the critical issue to realize the commercial exploitation of hydrates. Although hydraulic fracturing is one of potential stimulation methods, the occurrence environment of hydrate is not conducive to implement indoor experimental research and testing. Through physical properties determination and calibration, a pouring method of gas hydrate bearing sediment substitute has been optimized. We used the cured samples to prepare 25 * 50 mm standard cylinders and carried out triaxial shear test and porosity & permeability test. The physical properties test results show that the substitute corresponds well with the hydrate bearing sediments in the Shenhu area of the South China Sea. The stress-strain curve consists of three main phases, with strain softening occurring after initial plastic deformation. The cohesive force and internal friction angle correspond well to the actual hydrate bearing sediments by means of plotting Mohr circles. The substitute sample prepared by this pouring method can be used to carry out indoor fracturing experiment research, which is expected to promote the research progress of hydraulic fracturing of natural gas hydrate.

INTRODUCTION
Natural gas hydrate (NGH) is a clean energy source with high energy density composed of methane gas molecules and water molecules(Sloan, 2003). NGH resources are abundant and mainly distributed in terrestrial permafrost regions and shallow areas of the deep-sea continental shelf(Cai et al., 2020). Researches show that the global hydrate resources account for almost 1/2 of all energy resources in carbon reserves, and their effective exploitation is of great significance to alleviate the shortage of resources and realize sustainable development (Cui et al., 2019; Li et al., 2016).
Coupled THM Modeling of a Heated Borehole Test in Rock Salt
Authors: Tounsi H. , Rutqvist J. , Hu M. 
Published: September 2023

ABSTRACT
The very low permeability of intact salt rocks makes them promising media for the geologic disposal of nuclear waste. However, permeating flow can occur through fractures in rock salt. These fractures can be induced by excavation operations that create a localized damage rock zone where brine could migrate towards the excavation, or by strong temperature changes, around a high-heat emitting nuclear waste package, causing compressive (during heating) or tensile (during cooling) thermal stresses that could cause rock salt damage and a potential brine migration towards the heat source. Coupled thermo-hydro-mechanical simulations were performed to predict quantitatively the brine flow into a borehole excavated in rock salt as a result of excavation, heating/cooling and damage. The rate of water release was shown to rise with any change in temperature, with the greatest increase occurring during the cooling phase. Heating-induced compressive thermal stresses and creep caused the initial mechanical damage of rock salt, leading to the creation of higher-permeability zones (e.g., fractures) for pore water flow. The subsequent cooling led to an enhancement of these zones and the formation of additional ones as a result of tensile rock failure.

INTRODUCTION
Rock salt has been identified as a suitable medium for nuclear waste disposal due to its low permeability, high thermal conductivity, and self-sealing capacity (Sweet and McCreight, 1983; Cosenza et al., 1999; Winterle et al., 2012). However, micro-fractures in the salt host rock can compromise the hydraulic integrity of the disposal facility by providing pathways for brine migration (Hansen and Leigh, 2011). Micro-fracturing is often initiated by two phenomena: shear-induced dilatancy (Stormont, 1997) and tensile stresses exceeding the tensile strength of salt which is around 1 MPa (Hoffman and Ehgartner, 1998).
Several laboratory and in situ tests have been conducted in the 1990s or earlier to characterize the movement of brine in rock salt under isothermal and heated conditions (Hohlfelder and Hadley, 1979; Hohlfelder, 1980; Ewing, 1981; Krause, 1983; McTigue and Nowak, 1987; Finley et al., 1992). In the absence of heating, the brine inflow response varies from one experiment to another, mainly due to the heterogeneity of the tested rock salt formation that the excavation intersects (Finley et al., 1992). In the presence of a heating phase, the experiments show that brine inflow rates increase with an increasing borehole temperature (Hohlfelder and Hadley, 1979; Hohlfelder, 1980; Ewing, 1981; McTigue and Nowak, 1987). Additionally, some of these tests have shown that a considerable amount of brine was released during the heater shut-down (Hohlfelder and Hadley, 1979; Ewing, 1981).
Boundary Condition Effect on 3-Point Bending Test via FDEM
Authors: Huang Y. , Lei Z. , Rougier E. , Euser B. J. , Padilla A. M. , Knight E. 
Published: September 2023

ABSTRACT
Three-point bending test is a widely used laboratory test for the estimation of the flexural force-displacement response of the material. It is well known that the results of the three-point bending test are sensitive to the specimen and the loading. In this work, the impact of the boundary effects on a single notch three-point bending test is studied using LANL's combined finite-discrete element method (FDEM) based code, the Hybrid Optimization Software Suite (HOSS). To this goal, a series of virtual experiments with different specimens and boundary conditions are conducted. The influence of the notch location, and fixture shape are studied. Results clearly show that these boundary conditions greatly influence on the fracture initiation and propagation behaviors as well as the flexural force-displacement response.

INTRODUCTION
Three-point bending test is a long-used technique applied mainly in the oil and gas industry to estimate the fracture toughness of rocks in the laboratory. In this test, the vertical tension is applied to the convex side of a sheet or plate specimen placed on two supporting fixtures with a set distance apart.
A variety of numerical approached have been proposed to analyze the crack initiation and growth behavior of three-point bending test in the past several decades (Fakhimi, 2005; Kokot, G., Binkowski, 2011; Ramos, 2015; Klasztorny, 2018: Sauvage, 2020). However, the effect of boundary conditions is still lacking consideration in the previous studies.
Motivated by the prior works and the knowledge gaps remaining in effect of boundary conditions, a finite-discrete element method (FDEM) model is applied here to interpret three-point bending experiment results in order to characterize dependence of rock fracture behavior on boundary conditions and notch location. The present study therefore aims to capture the crack initiation and propagation behavior for laboratory experiments using material properties and traction-separation law that has been calibrated by comparing the simulation results with lab experiments provided by Jiang et al. (2021) and Jiang et al. (2022), regardless of notch location.
This study aims to revisit the effect of boundary conditions on crack initiation and growth behavior under three-point bending test. For this purpose, a 2D plane-strain model is developed using HOSS, a combined finite-discrete element method (FDEM) based code. Different boundary conditions and notch locations are considered for lab-scale simulations. Indeed, simulation results indicated that the crack initiation location and crack growth behavior can vary with different boundary conditions and notch locations, which can challenge the general belief that the crack initiation and propagation behavior should not be affected by the boundary conditions greatly.
Novel Approach for Elastic Anisotropy Assessment in Organic-Rich Shales: A Case Study from Early-Mature Region of the Bakken Formation
Authors: Malki Mohamed Lamine , Rasouli Vamegh , Latrach Abdeldjalil , Mellal Ilyas , Sennaoui Billel , Chellal Hichem A. K. , Larbi Anis 
Published: September 2023

ABSTRACT
The middle Bakken (MB) is a major unconventional oil producing formation in the U.S. with an enormous contribution of upper (UB) and lower (LB) Bakken members, source rocks. The three Bakken members form a crucial petroleum system in the Williston, where UB and LB, the target of this study, have similar lithologies, composed of siliceous, pyritic black shale, and middle Bakken (MB) which is a calcareous siltstone and fine-grained sandstone. Shales are characterized by their anisotropic nature due to layering. Therefore, isotropic modeling can lead to errors in stiffness estimations.
The main objective of this study was to develop anisotropic rock physics modeling of the Bakken formation to assess the elastic behavior and determine the key parameters controlling the velocity dispersion with respect to layering. Maturity effect was also investigated by including kerogen content into the system via solid substitution modeling. Laboratory data was scattered against the lab-scale rock physics templates to capture the dominant pores morphology with respect to beddings in the Bakken shale. Furthermore, this study captured the implications of different pore structures on controlling the degree of anisotropy in the medium. The results showed that UB and LB shales exhibit large anisotropy due to high presence of clay minerals, and fractures.

INTRODUCTION
The Bakken formation is a major oil producer in the U.S. The members constituting the Bakken formation are upper (UB), middle (MB), and lower (LB) Bakken members. Both UB and LB units, which are the subject of this study, are source rocks with similar lithologies, composed of siliceous, pyritic black shale (Laalam et al., 2022a; Malki et al., 2022a; Sennaoui et al., 2022a; Sennaoui et al., 2022c). Total organic carbon (TOC) in the Bakken shales may reach 40 wt.%, with potential oil in place in a range of 10-500 billion barrels (Aoun et al., 2023a; Ozotta, et al., 2022a; Sennaoui et al., 2023a; Sorensen et al., 2010), but ultra-low porosity and permeability characteristics (Afari et al., 2022; Laalam et al., 2022b; Ozotta et al., 2021c; Sennaoui et al., 2023b).
A Novel Rock Drillability Characterization and Prediction Method Based on Drilling Big Data and Unsupervised Clustering Algorithm
Authors: Lu Zongyu , Jiang Zhenxin , Wu Zhe , Song Xianzhi , Ye Shanlin , Liu Zihao 
Published: September 2023

ABSTRACT
Rock drillability measures the ability of rock to resist damage by the drill bit. Accurate evaluation of rock drillability is crucial for understanding formation properties and selecting appropriate drill bits and drilling parameters. However, many existing intelligent evaluation methods for rock drillability mainly rely on supervised learning algorithms, which require a large number of rock core samples for drillability analysis data as labels. Core acquisition is difficult and expensive. To address this issue, this study proposes a method for continuous formation drillability evaluation using logging big data and unsupervised clustering algorithms. Firstly, self-organizing mapping (SOM) neural network is used to cluster logging data. The formation is then divided into six drillability grades by analyzing the rate of penetration (ROP) distribution of each type of logging data. We used this method to grade the drillability of the test well formation. The results show that the ROP of the formation decreases gradually with the increase of drillability grade, which verproves the effectiveness of our method.

INTRODUCTION
Rock drillability is a crucial factor that determines drilling efficiency, reflecting how easily the rock breaks during drilling operations. Accurate evaluation of rock drillability can help drilling engineers select drilling tools and parameters to improve drilling efficiency (Kong, et al. 2022). The microdrill bit experimental method is a classic approach for evaluating drillability. It involves recording the time it takes for a miniature gear or PDC bit to drill 2.4mm under a specific drilling pressure and rotation speed condition, and calculating the formation drillability based on standard formulas and recorded time. (Zhang & Xue, 2019; Chen, et al. 2010). In the experimental method, the test rock core samples are not in the real underground environment, and the accuracy of the results is difficult to guarantee. Statistical analysis is another method for evaluating rock drillability, which predicts the drillability of rock by establishing a mathematical model that incorporates logging data, drilling parameters, and other factors that influence drillability (Andrews, et al.; Tang, et al.). However, a significant amount of rock core data is required to support the model and ensure accurate predictions.
Impact of Pore Structure on Stress-Dependent Behavior of Permeability for Fluid Flow Through Porous Medium
Authors: Wang Xiaohan , Peng Yan , Lyu Peihong 
Published: September 2023

ABSTRACT
Stress-dependent behavior of permeability is an important characteristic of fluid flow through porous medium. It is widely accepted that the stress-dependent permeability behavior relates to pore volume change, but ignore the real stress distribution around pores. In this study, the coupled flow-geomechanics numerical simulation is conducted to simulate the real process of fluid flow through a real pore structure. The fluid flow inside pores is described by the laminar flow, and calculate the pore volume change by elasticity theory. Permeability is calculated by Darcy's law. The affections of pore structure on stress-dependent permeability behavior are studied and then main factors affecting this behavior are discussed. The main results show: (1) There is a dominant cross-section in the whole pore controlling the stress-dependent behavior of permeability. This dominant cross-section may be the cross-section where the flow velocity is highest along the pore. (2) The three stress components have different impacts on permeability stress-dependent behavior. The major stress component can be determined through the deformation of dominant cross-section which is the dominant one for permeability. (3) The pore geometry shape also affects stress-dependent permeability. (4) The pore's orientation also affects stress-dependent permeability behavior.

INTRODUCTION
Rock is a typical porous medium consisting of pores and a solid skeleton. Rock permeability is one of the most important fluid transport properties. Stress-dependent behavior of permeability significantly affects fluid flow behavior of in areas of underground storage, petroleum engineering and mining engineering. The rock permeability is determined by the connected pores and their distribution in the rock. Based on the rock mechanics theory, pore shape can cause stress concentration affecting pore deformation (Peng et al., 2021). The stress-dependent behavior of permeability results from pore deformation (Peng et al., 2022). In addition, the stress-dependent behavior of permeability is also affected by the stress variation. The in-situ stress of unconventional reservoirs varies significantly after many treatments, such as hydraulic fracturing and water flooding (Pan et al., 2012; He et al., 2020; He et al.,2020). Therefore, the stress-dependent behavior of permeability affects production behaviors of unconventional reservoirs.