bluuebunny/crossref_metadata_2025_split huggingface dataset:
Log-Log Analysis for Compaction Damage Evaluation Caused by Pores Collapse in Depletion-Dependent Oil Reservoirs
Authors: Fernandes F. B. , Gildin E. , Braga A. M. B. , Duarte M. C. 
Published: August 2024

ABSTRACT:
The impact of the mechanical formation damage in the production curve caused by the transient permeability hysteresis in pressure-sensitive reservoirs has an important role in oilfield developments. Hence, the petroleum industry has continuously sought new analytical approaches to provide adequate, well-reservoir performance management and surveillance. This work proposes anew transient two-dimensional (2-D) analytical solution for modeling the oil flow in a permeability hysteretic pressure-dependent reservoir during alternating loading/unloading cycles. The nonlinear hydraulic diffusivity equation (NHDE) is perturbed through a first-order asymptotic series expansion technique. The reservoir engineering literature shows that this first-order expansion represents the magnitude of the nonlinear phenomena regarding pressure-sensitive rock and fluid properties. A new hysteretic deviation factor is presented for flow (drawdown) and buildup periods. This deviation factor represents the permeability deviation during the drawdown and its partial restoration in the buildup period. A set of pressure and permeability field data is used as input to the computational code. The model calibration is performed by a porous media numerical oil flow simulator named CMG IMEX®, broadly used in formation evaluation and reservoir engineering literature. The results presented high accuracy for the drawdown and buildup of hysteretic and non-hysteretic cases.

1 INTRODUCTION
The mathematical modeling of the production loss caused by the reservoir compaction damage is essential to prevent premature well abandonment and field disinvestment (Fernandes, 2022; Fernandes and Braga, 2023).
The Hydraulic Diffusivity Equation (HDE) models the isothermal, single, and multi-phase flow in porous media. It is derived from the coupling of Darcy's law, continuity equation, and porous media constitutive equations for rock and fluid properties (Matthews and Russell, 1967). Often in the petroleum engineering and dynamics of fluids in porous media scientific literature, the Linear Hydraulic Diffusivity Equation (LHDE) is solved through Laplace and Fourier transform or Boltzmann transformation, (Everdingen and Hurst, 1949; Matthews and Russell, 1967; Peres et al., 1989).
In order to achieve cost savings and accurate model demand, analytical solutions for the Nonlinear Hydraulic Diffusivity Equation (NHDE) have been studied for many years by geoscientists, well-testing, and reservoir engineers.
An Innovative Combination of Scratch Test and Weibull's Statistical Fracture Theory
Authors: Zhang Yazhou , Jin Yan , Sun Xiuxia , Zeng Ping 
Published: August 2024

ABSTRACT:
The scratch test is fast and reproducible, as confirmed by recent research. To evaluate the high consistency of these two methods, which is scratch and uniaxial compression, respectively, the comparison of strengths have been conducted. Scratch tests are performed on Gulong shale and sandstone, and the statistical analysis of the experimental results is carried out detailly, which further reveals the longitudinal heterogeneity of Uniaxial Compressive Strength (UCS) of the rock samples. Besides, the original tensile stress state of Weibull distribution is extended to a compressive stress state, and a UCS-based model of Weibull distribution is developed and validated. The results provide evidence that the UCS profiles of sandstone and shale, can be considered to follow the two-parameter Weibull distribution with a significance level of 0.05. In conclusion, the scratch test provides an effective approach to obtain the continuous high-resolution UCS profile of the rocks. Meanwhile, the combination of the scratch test and the Weibull's theory, can further contribute innovative ideas and methods to clarify the geomechanical characteristics of the reservoirs.

1. INTRODUCTION
As a natural heterogeneous mixed material, rock is of great interest to us, and the effective determination of its properties is indispensable in many fields. In particular, the accurate test of strength[1-3] is very important.
Traditionally, Uniaxial Compressive Strength (UCS), is usually performed on a rigid servo testing machine[4]. However, this test is destructive, relatively time and cost consuming. Recently, the development of Continuous Scratch Testing (CST) techniques[5-7] has provided us with a powerful and fast strength testing method. Based on the strong correlation between specific energy and UCS[8], CST can offer us a continuous high-resolution UCS profile, which can be understood as the point strength located in each microcell of the rock sample. In this way, a large number of specimen data can be obtained at low cost, which can support other studies easily.
This principle coincides with the content of the Weibull's statistical fracture theory. Weibull distribution data set only needs the critical stress of each microcell for rocks, even if it is based on the assumption of tensile stress initially. For the Weibull distribution, which is mainly used for reliability analysis and life estimation, it has been studied by large numbers of scholars, who developed the theory[9] and tried to combine it with rock mechanics tests[10,11]. And, many achievements have been made.
Effects of Epidote and Chlorite on the Frictional Stability of Granite Faults: Implications for Seismicity in Deep Geothermal Reservoirs
Authors: An Mengke , Zhang Fengshou , Huang Rui , Elsworth Derek 
Published: August 2024

ABSTRACT:
Epidote and chlorite are both low-grade metamorphic minerals that are widely distributed in deep granite geothermal reservoirs. Hot fluid circulation promotes the precipitation of epidote and chlorite coatings on natural faults and fractures and this can in turn exert control on fault/fracture frictional stability. We use simulated epidote/chlorite gouges and conduct fault shear experiments at conditions typifying the ∼4 km depth typical of deep geothermal reservoirs to explore the effect of epidote/chlorite content on frictional strength and stability. Results indicate that the frictional characteristics of epidote and chlorite gouges vastly differ. Epidote gouge is frictionally strong, with a coefficient of friction of ∼0.73, nearly double that of the chlorite gouge (∼0.35). In addition, the epidote gouge exhibits strong velocity-weakening and unstable frictional behavior under the test conditions, while the chlorite gouge is velocity-strengthening and stable. Fault frictional strength and velocity-weakening behavior are all enhanced for epidote-granite mixed gouges as epidote content increases. However, chlorite-granite mixed gouges show the opposite trend with increasing chlorite content. Our results have important implications in understanding the frictional stability of epidote/chlorite-filled granite faults and its influence on seismicity in deep geothermal reservoirs inhabiting the shallow crust.

1. INTRODUCTION
The moment magnitude (Mw) 5.5 Pohang earthquake that occurred in November 2017 has been demonstrated as one of the largest and most damaging earthquakes on the Korean peninsula since the last century (Grigoli et al., 2018; Kim et al., 2018). This event has attracted widespread attention not only for the significant resulting hazard and damage but also due to its connection with the Pohang Enhanced Geothermal System (EGS) project in South Korea. This earthquake (Lee et al., 2019a) directly injured &gt;100 people and resulted in &gt;US$300 million in economic loss, and it is also the largest known injection-induced earthquake at an EGS site. Currently, it has been confirmed that an unmapped pre-existing critically-stressed fault was reactivated at a depth of ∼4.0 km by the fluid injection during EGS stimulation and finally trigger the seismicity (Lee et al., 2019a).
Hydration Impact on Pore Structure and Methane Adsorption in the Lower Silurian Longmaxi Shale of the Sichuan Basin
Authors: Wang Duo , Yuan Hang , Wei Shuijian , Li Xiao 
Published: August 2024

ABSTRACT:
For shale gas reservoirs in the Sichuan Basin of China, renowned for low water saturation and complex pore structures rich in clay minerals, exhibit significant fluid imbibition post-hydraulic fracturing. This study delves into the Longmaxi Formation shale in the Sichuan Basin, China. Employing quantitative isothermal adsorption techniques, it elucidates pore structure alterations pre- and post-hydration. Quantification of the impact of fluid imbibition on different pore sizes was conducted. It was found that the influence on organic matter pores and macropores larger than 50 nm was minor, whereas the effect on clay inorganic matter pores in the range of 2-30 nm was most significant. Additionally, the influence of water saturation on methane adsorption capacity was quantified. With increasing water saturation, methane adsorption exhibited a nonlinear decreasing trend. An empirical formula was established to predict the adsorbed gas content evolution based on pore structures ranging from 0 to 20 nm under shale imbibition conditions. The reservoir methane adsorption capacity was calculated based on different soaking times, indicating that the reservoir's adsorbed gas content exhibited the highest desorption efficiency after 6 days of soaking.

1. INTRODUCTION
Shale oil and gas originate from organic-rich hydrocarbon source rocks characterized by low porosity, low permeability, integrated source-reservoir systems, and developed bedding structures (Jarvie et al., 2003). In the development of shale oil and gas, horizontal well multi-stage fracturing technology is commonly employed to enhance production artificially (Curtis, 2002; Zhao et al., 2018). Furthermore, due to hydrocarbon generation pressure and gasification-driven liquid carrying effects in shale reservoirs, they often exhibit extremely low water saturation characteristics (Bennion et al., 2000; Bennion & Thomas, 2005). Moreover, shale composition and pore systems are highly complex, consisting of micro-nano pores in organic matter and inorganic pores in clay minerals and brittle minerals (Han et al., 2020; Xie et al., 2022), leading to strong water absorption capabilities in shale (Minardi et al., 2018; Zeng et al., 2021).
A Cross-Scale Characterization of Porous Rocks Altered by Flow and Dissolution
Authors: Xu Z. , Li W. , Kolanti A. , Sprouster D. 
Published: August 2024

ABSTRACT:
Flow and dissolution induce wormholes in porous rocks, which lead to a substantial increase in both permeability and flow heterogeneity of the rock formation. Wormholes originate from the initial micron-scale pore networks, and gradually transition to more prominent millimeter-scale holes. Wormholes have a crucial impact on the flow and reactions in subsurface technologies, such as critical mineral leaching, CO2 storage and reservoir stimulation. Understanding how wormholes form from pore networks is crucial for the effectiveness of these subsurface technologies. However, current studies are limited to two separate scales of characterizations: millimeter-scale wormholes and micron-scale pore networks. The transitional region, which bridges these features at the two scales, remains largely unexplored and inadequately characterized. This knowledge gap obscures our understanding of the underpinning physics that governs wormhole formation in porous rocks. In this study, we aim to bridge these two scales of study with multiscale characterization. We create wormholes in porous gypsum specimens through core flood tests. The wormholes are then scanned with low-resolution (26.70 μm) and high-resolution (3.43 μm) X-ray computed tomography (CT). We quantitatively characterize the geometry of the wormholes leading to pore networks regarding their diameters, and quantities. This 3D cross-scale characterization allows for an accurate depiction of the interactions between wormholes and pore networks and provides physical insights into the initiation of wormholes.

1 INTRODUCTION
Wormholes are long and finger-like channels resulting from the heterogeneity in flow and dissolution within a porous medium (Szymczak and Ladd, 2009; Li et al., 2022). Wormhole formation is common in many natural and industrial processes, such as enhanced oil production and CO2 storage (Hoefner and Fogler, 1988; Gouze and Luquot, 2011; Smith et al., 2013; Menke et al., 2015; Wang et al., 2016). Wormholes significantly increase the permeability of the porous media and localize the flow and consequently heat and mass transfer between the fluid and porous media. Understanding how the wormholes emerge and quantifying their impact on the porous media during the subsurface resource exploitation are crucial in the engineering of the aforementioned subsurface systems.
Four-Dimensional Stress Evolution and Optimization of Child Well Fracturing Parameters in Multi Sub-Layers Shale Gas Reservoir
Authors: Yang Haixin , Tang Xuanhe , Zhu Haiyan , He Xiao , She Chaoyi , Zheng Majia , Wu Jianfa , Song Yi , Huang Haoyong , Li Junfeng , Wang Dajiang , Li Yuanzhao , Song Junbei 
Published: August 2024

ABSTRACT:
The research is aimed at the first infilled multi-well pad in deep shale gas reservoir of Sichuan Basin China. Since parent wells are not able to improve producing reserves of the pay zone, the deployment of infill wells is imperative. Therefore, the effect on infilled well fracturing caused by parent well's pressure depletion need to be investigated. This paper calculates the four-dimensional in-situ stress evolution by a comprehensive numerical model. And then several fracturing parameters of infilled well are optimized from two aspects: fracture geometry and stress disturbance range. The results show that: Stress disturbance range in horizontal is about 1.6 times of fracture length, in vertical is approximately equal to fracture height. For the infilled well, W-type well pattern and cluster spacing 15m are more suitable, the best fracturing time is about 24 months after the production of the parent well.

1. INTRODUCTION
Based on the practical experience in the development of medium-shallow shale gas, the well spacing less than 300m is generally adopted for deep shale gas in China to improve producing reserves. However, due to the limited comprehension of the geomechanical characteristics, the horizontal and vertical stress disturbance range of parent wells are not able to cover the inter-well pay zone. At the same time, the hydraulic fracture height failed to achieve the expectation and also failed to cover the entire pay zone in vertical direction. Based on this, infill wells must be deployed above the parent wells on the top of main pay zone to achieve the purpose of increasing the reserve control range of the well group in vertical and horizontal. As the production of shale gas wells decreases by more than 50% in the first three years, there is a pressure drop of up to 20MPa in the reservoir around the parent well. The depletion of pore pressure affects the in-situ stress, causing the in-situ stress of the reservoir to continuously change over time (i. e. four-dimensional in-situ stress), leading to interference with the parent well during fracturing of the filling well, and even causing fracturing hits. Resulting in a sudden decline in the production of the old well. This is a new problem restricting the sustainable and efficient development of shale gas in China.
Fluid Geochemical Genesis of the Rehai High Temperature Geothermal System in the Southeast Himalayas
Authors: Liao Dawei , Wang Yingchun , Hao Yinlei , Feng Jianyun , Zhang Ying 
Published: August 2024

ABSTRACT:
Western Yunnan is located in the southeast Himalayas, with well-developed faults and abundant high-temperature geothermal resources. In the western Yunnan geothermal fields, the hydrochemical and isotopic characteristics of geothermal fluids are studied and analyzed, elucidating the genetic model of magmatic high-temperature geothermal systems, and revealing the hydrochemical processes and genesis of geothermal water during the circulation process. The Rehai geothermal water type is mainly HCO3 Cl-Na. The high Cl content of geothermal water comes from the supply of magmatic water, while Na, K, and HCO3 mainly come from the leaching of feldspar minerals by mantle-derived CO2. Water hydrogen and oxygen isotopes indicate the source of atmospheric precipitation, while Rehai hot spring water shows an "18O shift". It is related to the mixing of magmatic water and the interaction between water and rock. According to the Na-K cation thermometer, among numerous geothermal fields of the western Yunnan region, the deep reservoir temperature of the Rehai geothermal field is the highest, reaching 260 °C. The Rehai geothermal water undergoes deep circulation and obtains deep heat after being recharged by atmospheric precipitation infiltration in the metamorphic rock area of the Gaoligongshan group located in the northeastern mountainous area. Rising along the fault, exposed as a hot spring at the surface.

1. Introduction
Under the combined action of the collision between the Indian and Eurasian plates and the westward subduction of the Pacific plate, a Cenozoic orogenic belt belonging to the Tethys tectonic domain has developed in the southwest region, while a Mesozoic Cenozoic fault basin group belonging to the Pacific Rim tectonic domain has formed in the eastern region. It belongs to the Mediterranean Himalayan and Pacific Rim geotropics, respectively, which have shaped the highest heat flow in Southwest China and Taiwan, with higher heat flow in the east and lower heat flow in the central region. It controlled the enrichment of deep geothermal resources in China. The Indian Plate drifted northward and collided with the Eurasian Plate (Chen et al., 2015; Tang et al., 2017; Zhou et al., 2017). It subducted towards its lower part, causing the lower edge of the Eurasian Plate to be heated and melted, and to invade along the weak structural zone of the upper plate, which provided a very favorable tectonic background and heat source conditions for the formation of diverse geothermal activities in the western Yunnan region on the southeastern edge of the Himalayas. From the perspective of geothermal flow, western Yunnan is one of the most favorable regions for geothermal formation in China The average heat flow value in the southwestern region of Yunnan Province is 75 mW/m2, while the heat flow value in Tengchong County is 93 mW/m2, which is the highest in Yunnan (Figure 1).
Caprock Stress Contrast Measurement, Mechanism Investigation and Development of Area In-Situ Stress Characterization, Northern Lights CCS, Offshore Norway
Authors: Thompson N. , Meneguolo R. , Rasmussen S. , Bautmans P. , Reitan H. , Stroisz A. , Cruz L. 
Published: August 2024

ABSTRACT:
This work, focused on the Northern Lights CCS project (offshore Norway) builds upon the recognition by Thompson et al. (2022) of stress contrasts within a CO2 storage caprock shale by introducing newly collected in situ data and laboratory testing. Specifically, carefully designed in situ testing (microfrac) was performed to validate the stress contrasts suggested from the exploration/appraisal well observations, as well as full log suites obtained to investigate stress profiles. Laboratory tests, focusing on the degree of relative creep between the identified shale intervals, was performed to better understand the mechanism behind the stress contrasts observed. A viscoelastic stress relaxation approach is then used to characterize in situ stress from experimentally obtained creep parameters. In total, the stress contrasts are again observed through all methods, with a high consistency from well to well. A connection to mineralogy is further validated, where increased creep higher clay content is observed to result in higher relative minimum formation stress. These collective observations bring confidence that higher minimum formation stress is present in the caprock, allowing the project to define CO2 safe storage potential more confidently in the structure.

1. INTRODUCTION
As a means of achieving IPCC targets of reducing net atmospheric carbon emissions, carbon capture and storage (CCS) is experiencing rapid growth; project development activity has increased significantly in recent years, towards a projected storage need of upwards of 10 Gt/yr by 2050 (IPCC [2018], IEA [2021] Global CCS Institute [2023]). The Longship (including CO2 capture) and Northern Lights projects (CO2 transport, temporary storage and subsea pipeline transport to permanent subsurface storage) are frontrunners in this industry, realizing the full CCS value chain through establishment if capture sites at various industries, transport ships, a temporary storage facility and subsea infrastructure off the coast of Norway (Northern Lights JV DA [2024], Gassnova [2024]). Phase 1 of the project (up to 1.5 Mt/yr storage, for 25 years) is ready to receive CO2 in 2024.
Improving Rock Excavation Efficiency Through Monitoring of Pick Cutter's Wear Condition
Authors: Morshedlou A. , Dagli I. , Rostami J. , Moradian O. , Belviranli M. 
Published: August 2024

ABSTRACT:
In underground soft rock mines, continuous miner and similar machines are operated by a operator at the cutting face looking for visual cues to control the operation, exposing them to potential dangers. One approach to improve operator safety is to relocate them away from the working face, allowing remote operation. This paper explores how automation can enhance mine health and safety by monitoring cutting forces on pick cutters to detect bit wear conditions. This approach not only boosts safety but also increases the efficiency of the excavation process. For this purpose, full-scale cutting tests were conducted using various types of conical pick cutters in different wear conditions (new, moderately worn out, and worn-out) in different rock types. The goal is to understand wear conditions based on cutting forces, enabling remote assessment of pick cutter wear conditions. Machine learning classification algorithms, including support vector machines (SVM), K-nearest neighbors (KNN), random forest, naïve Bayesian, extreme gradient boost (XGB), and neural networks, were employed. The SVM model demonstrated superior performance, achieving an accuracy and F1-score of 80.95%. Lastly, the trade-off between accuracy and execution time for real time identifications of rock type and calculation of wear status have been conducted and presented in this paper.

1. INTRODUCTION
The working conditions in underground mines including coal/rock dust, methane emission, roof collapse and rock falls can compromise miners' health and safety. According to data from the Mine Safety and Health Administration (MSHA) and the US Bureau of Labor Statistics, 2023 saw the highest number of fatalities in the mining industry in the past ten years, with a total of 40 fatal injuries, nine of which occurred in coal mines. Over the past decade, coal mining has accounted for an average of nearly 36% of all fatal injuries in the mining industry. Added to this is the harmful working conditions that can impact miners' health such as respiratory illnesses and hearing losses.