bluuebunny/crossref_metadata_2025_split huggingface dataset:
Research on the Mechanism of Fracturing Fluid's Influence on Mechanical Properties of Sandstone
Authors: Liu Hanbin , Chen Houze , Wang Yajuan , Mou Chunguo , Zhao Qianyun , Ma Huan , Liu Qian 
Published: September 2023

ABSTRACT
Fracturing fluid is the main cause of reservoir damage during hydraulic fracturing. Fracturing fluid will change the mechanical properties of reservoir rock, and the effect of proppant-propping hydraulic fractures will be affected. To study the changes and internal mechanism of sandstone mechanical properties after guar gum fracturing fluid damage, triaxial compression experiments, core flow experiments, scanning electron microscopy, and nuclear magnetic resonance tests were carried out on sandstone cores before and after damage. The results showed that: (1) The compressive strength and elastic modulus of sandstone decreased after guar gum fracturing fluid damage, which was caused by the increase of the average pore radius of the rock and the weakening of the interaction between particles. (2) The changes in sandstone microstructure after fracturing fluid damage are as follows: rock particle migration, fracturing fluid macromolecule residues, and the proportion of micro-pores decrease (11%). (3) Tight sandstone is more sensitive to guar gum fracturing fluid, and the lower the initial permeability of sandstone, the greater the decrease in compressive strength and elastic modulus after damage. (4) The change of rock mechanical properties is positively correlated with the range of permeability change. It is of great significance to consider mechanical properties as a factor in the study of fracturing fluid damage.

INTRODUCTION
Unconventional tight sandstone gas has become a natural replacement area for natural gas exploration and development. According to the fourth national oil and gas resource evaluation results, in the tight gas field, the currently proven recoverable reserves are 3.96×1012m3, accounting for 33% of the total proven resources and the remaining recoverable resources are 6.97×1012m3. From the distribution of remaining resources, the future tight gas exploration areas are still concentrated in the Ordos and Sichuan Basins (Zheng Min, 2019). The low-permeability tight gas reservoirs in the Ordos Basin have large reserves. However, they have poor physical properties, substantial heterogeneity, low reserves, and significant differences, and it is not easy to achieve long-term stable production and profitable development of gas reservoirs (Cheng Lihua, 2020).
The Role of Water in the Dynamic Mechanical Behaviors of a Granitic Rock
Authors: Yang H. , Cai G.-L. , Zhao Q. 
Published: September 2023

ABSTRACT
Rock masses are frequently exposed to dynamic stress perturbations associated with natural events (e.g., earthquakes, landslides, and rock bursts) and engineering operations (e.g., blasting, explosion, and induced earthquakes). Understanding the dynamic mechanical characteristics of rock masses is essential to many geo-engineering applications such as underground excavation and hydrocarbon energy exploitation. Water is ubiquitous in the Earth's crust and plays a vital role in the dynamic mechanical behaviors of rock masses; hoever, the effects of water on the dynamic mechanical characteristics of rocks are still not fully understood. Therefore, it is necessary to carry out more dynamic tests to understand their mechanical responses to the presence of water. To this end, we conduct dynamic uniaxial compressive tests on dry and water-saturated granite rock samples via the split Hopkinson pressure bar (SHPB) technique. The test results demonstrate the strain rate dependence of dynamic mechanical properties of both dry and water-saturated granite rock specimens. The presence of water lowers the dynamic compressive strength and elastic modulus of granite rock specimens. The dynamic increase factor (DIF), characterizing the strain rate sensitivity of dynamic mechanical properties, for wet granite rock specimens is higher than that for dry ones over the tested strain rate range. These findings improve our understanding of the water effects on the dynamic mechanical behaviors of granite rocks.

INTRODUCTION
Dynamic loading is commonly encountered in natural activities, such as earthquakes and volcanic eruptions, and in engineering operations, such as rock blasting and hydraulic fracturing (Elsworth et al., 2016; Zhang & Zhao, 2014; Bažant & Caner, 2013). Such dynamic disturbance could strongly affect the mechanical behaviors of rock masses, causing the deterioration and damage of rock supports and structures. Understanding the dynamic mechanical behaviors of rocks is therefore essential for the design, construction, and maintenance of tunnels and caverns, defense and military infrastructures, mining facilities, etc. (Li et al., 2017; Qian & Lin, 2016; Zhao et al., 1999). Moreover, dynamic loading at high strain rates could be one of the origins of rock pulverization identified near the active faults, a marker of coseismic damage due to strong earthquakes (Aben et al., 2017; Doan & Gary, 2009). The knowledge concerning rock mechanical responses to dynamic loading could provide insights into rock pulverization, advancing the understanding of earthquake physics and seismic faults (Smith & Griffith, 2022; Griffith et al., 2018; Aben et al., 2016). In this context, more and more attention has been paid to the mechanical behaviors of rocks subjected to dynamic stresses.
Preliminary Study on a Strong Sand-Carrying and Low Damage Viscoelastic Slickwater Under a Wide Shear Range
Authors: Bai Hao , Zhou Fujian , Wu Junlin , Li Bojun , Wang Bin , Xu Hang , Wang Wenzhong , Lang Hao , Yao Erdong , Wang Jiachen 
Published: September 2023

ABSTRACT
Slickwater or linear gel is often used for fracturing development in tight sandstone reservoirs. As it carries sand into the formation through the wellbore, its sand-carrying performance changes with the continuous change of liquid shear rates. In this paper, a new type of viscoelastic slickwater is proposed, which avoids the problems of low sand-carrying capacity of conventional slickwater and large damage of guar. Through theoretical calculation, taking the injection rate of 10 m3/min as an example, the maximum shear rate of fracturing fluid in wellbore and fracture is 884.82 s−1 and 8.33 s−1 respectively. Viscoelastic slickwater polymer is physically cross-linked and reversible associated to form a network structure. It has excellent shear resistance at different shear rates (0.01∼1000 s−1). The intersection point of viscoelastic modulus is lower than 0.021 Hz, and the viscoelastic performance is excellent. Under the low shear rates of fracture (0.01∼10 s−1), the performance of viscoelastic slickwater suspended sand is excellent, and the equilibrium height of sand bank is lower than 26.7% of fracture height. Under the high shear rates (10∼1000 s−1) in the wellbore, its viscosity is high, and the friction reduction rate can reach 81.59%. In addition, it breaks quickly, the amount of residue is low, and the conductivity can be retained by more than 90%. Under field application, the sand concentration of the system is as high as 300 kg/m3, and the production of vertical well after fracturing can reach 0.96 tons/day in more than one year. Viscoelastic slickwater can realize friction reduction and sand carrying at the same time, which has the value of popularization and application.

INTRODUCTION
The tight sandstone reservoir has features of tight lithology, low porosity, and low permeability, and others, mainly secondary porosity, and high feldspar and cuttings content. Due to low reservoir pressure coefficient, its natural productivity is low (Wang et al., 2022; Zhong et al., 2022). Compared with conventional reservoirs, tight sandstone reservoirs have staggered pore distribution and poor connectivity, high water saturation, strong stress sensitivity, and limited recovery by conventional oil displacement methods (Xie et al., 2022; Dong, et al.,2019). Therefore, new unconventional reservoir stimulation technologies and measures are urgently needed.
Numerical Study on Permeability Evolution of a Natural Fracture in Granite During Shearing
Authors: Li X. , Zhang F. , Du M. , Xiu N. , Weng D. , Cai B. , Fu H. , Huang L. 
Published: September 2023

ABSTRACT
The permeability evolution of natural fractures during shearing is one of the critical issues in enhanced geothermal system (EGS). In this study, a series of numerical simulations of shear-flow tests under different normal stresses were carried out to investigate the permeability evolution and shear behavior of a natural fracture during shearing. All numerical simulations in this study were implemented based on a coupled hydro-mechanical pore network model (PNM) of fluid flow in discrete element method (DEM). Fluid grids in the simulations are continuously refreshed as the shear progresses. The results indicate that the fracture permeability positively correlates with the shear displacement when the normal stress is relatively large. The essence of permeability evolution is the variation of the local aperture distribution. Greater fracture roughness makes it easier to form high-permeability pathways. Besides, high normal stress amplifies the effect of fracture roughness on permeability evolution. These findings can contribute to a better understanding of the hydraulic-mechanical coupling effects in the fracture shearing process of EGS.

INTRODUCTION
Enhanced geothermal system (EGS), as a key technology for the extraction and utilization of geothermal energy from high-temperature rock masses in deep formations, has become a research and development hotspot in the field of earth energy and renewable energy (Huang et al., 2018). Many studies have shown that fluid injection in EGS may lead to induced seismicity (Hanano, 2004; Zang et al., 2014; Gaucher et al., 2015; Kim et al., 2018). EGS utilizes fluid to create a new fracture network in hot dry rock or to further expand the original natural fracture network, thereby creating a large number of fluid flow channels. This process involves a series of complex fluid-solid coupling effects and may cause shear slips of fractures or faults (Ishibashi et al., 2018). Fracture shear slip is often accompanied by the evolution of fracture permeability, and the evolution process of fracture permeability can reflect the frictional stability of fractures to a certain extent (Wu et al., 2017). It can be seen that the study of the permeability evolution process and its influence factors in the shearing process of natural fractures is of great significance for evaluating the safety and stability of EGS.
Development and Optimization of Epoxy-Resin Based Cement Reinforced with Low-Cost Fly Ash for High Durability Environmentally Friendly Cement
Authors: Fakher Sherif , Tamer Sara , Eltohamy Mohamed , Ali Mahmoud , Alsakkaf Aseel , Gehad Mennatallah , Haydar Raz , Mourad Karim 
Published: September 2023

ABSTRACT
Cementing is an integral operation in any oil and gas well. Although conventional cement has been used for many years, it suffers from two significant problems. These include significant numbers of failures especially at extreme conditions, and environmental damage due to high emissions generated during cement production. This research overcomes these two problems by developing a novel environmentally friendly and high durability epoxy based cement reinforced with low cost fly ash. More than 100 different samples were prepared for the novel cement for evaluation. Different formulations were designed for testing by varying the fly ash concentration. The formulations had a fly ash concentration of 0, 10, and 30%. The samples were tested under temperatures of 25, 80, 120, and 160 °C, and hydrochloric acid (HCl) concentrations of 1, 10, and 20%. The samples were also tested for sedimentation, and density increase with the increase in fly ash concentration. Compared to the conventional class G cement, the developed cement showed higher acid and alkali resistance, higher thermal stability, and much higher overall compressive strength.

INTRODUCTION
After an oil well is drilled, metal piping called casing is placed in the hole to support the drilled hole from collapsing. In order to fix the casing to the hole wall, cement is used. The cement must have unique properties to avoid problems (Fakher, et al., 2020; 2021; 2022). These properties include high compressive and tensile strength, high bond strength with the casing and the formation, low porosity and permeability to avoid fluid migration through the cement, and high resistance to temperature, acidity, and alkalinity to avoid cement interaction with different underground fluids (Wagle, et al., 2021; Fakher, and Khlaifat, 2022). Although conventional cement has been used for many years in oil and gas wells, it suffers from two main drawbacks. Firstly, conventional cement relies on limestone as its raw material; this results in an ever-increasing cost of cement and the large volume of greenhouse gas emissions associated with the burning of the limestone to produce cement (Alanqari, et al., 2022; Lummer, et al., 2017; Fakher, 2020). Secondly, with the increase in technology, deeper wells are being drilled with more extreme conditions which results in cement failure. It is therefore necessary to produce enhancements to the cement in order to be able to withstand these severe conditions.
Pore Pressure Detection Method of Carbonate Formation Based on Multiple Logging Parameters
Authors: Lv Kunhong , Zhang Hui , Ouyang Yong , Lu Zongyu , Shi Jiangang 
Published: September 2023

ABSTRACT
Prediction methods for the pore pressure of clastic rock formation are almost mature worldwide. However, due to the characteristics of carbonate rock formation, such as high matrix rigidity, pronounced heterogeneity, and the uncertain formation mechanism of abnormal pressure, the traditional prediction methods of formation pore pressure are difficult to apply in carbonate formation, which seriously threatens the drilling safety. Therefore, the method for calculating the pore pressure of carbonate formation was studied. Taking the carbonate formation of the Majiagou Group in the Mid-Eastern Ordos Basin as an example, this paper put forward a comprehensive interpretation of various logging parameters related to the formation mechanism of abnormal pressure. It established a pore pressure prediction model applicable to carbonate formation, which is not limited to the under-compaction theory using multiple nonlinear regression methods. The formation pore pressure detection method was applied to multiple wells in the Majiagou Group, Mid-Eastern Ordos Basin. The application results showed that the relative error of formation pore pressure between the model detection and measured values was less than 10%, which satisfy engineering requirements. It also provides a new approach to address the problem of pore pressure detection of carbonate formation.

INTRODUCTION
Abnormal high pressure has an important impact on the development of conventional and unconventional oil and gas reservoirs, which may cause many complex accidents, such as wellbore instability, drilling fluid leakage, and blowout. With the development of oil and gas reservoirs towards the complex formation, formation pore pressure prediction plays an increasingly important role in the future development of oil and gas reservoirs. Reasonable and accurate prediction of formation pore pressure is the basis for the rational design of drilling fluid density, wellbore structure design, and wellbore pressure maintenance. It also guarantees safe, effective, and rapid drilling. Formation pore pressure prediction includes forward-looking pre-drilling prediction, timely monitoring while drilling, and reference post-drilling detection. Among them, the accuracy of post-drilling detection is the highest. The logging data of adjacent and exploratory wells can provide theoretical support and reference for target wells’ formation pore pressure prediction.
Wellbore Stability of Mud-Shale in Ultra-Deep Carboniferous Formation: A Perspective from Mechanochemistry
Authors: Zhen Zhang , Jiaxin Li , Yong Sheng , Lin Chen , Zheng Fang , Yunhu Lu 
Published: September 2023

ABSTRACT
The wellbore instability is a vital problem when drilling in the ultra-deep carboniferous shale formation in the southwest block of Tarim Oilfield. And, bits are frequently blocked and stuck. Unfortunately, the problems are hardly to be effectively solved by increasing the drilling fluid density. At present, the mechanism of wellbore collapse in the block is still unclear. In this way, it is unable to establish an effective prediction model for wellbore collapse. Therefore, this paper systematically analyses the formation mineral characteristics, physical and chemical properties and stress state in the block to clarify the reasons for wellbore instability of mud shale formation. Consequently, the wellbore stability model of mud shale is established considering the degree of formation collapse, drilling fluid density, activity and plugging. Then, through quantitative analysis and definition of the relationship between the wellbore collapse degree and the density and performance of drilling fluid, the technical countermeasures for wellbore stability are proposed. The analysis model proposed in this paper provides a new way for quantitative design of drilling fluid density and performance in ultra-deep carboniferous mud shale formations.

INTRODUCTION
Based on statistics, the confirmed recoverable reserves of deep oil and gas reach up to 7.29×1010 t oil equivalent, constituting 49.07% of the world's total recoverable reserves. As much as 70% of China's unconventional oil and gas resources are stored in deep formations, leading to a growing number of ultra-deep wells drilled(Chen et al., 2009; Y. Lu et al., 2011; Zhang et al., 2022). The Tarim Basin in China is a significant region for its vast oil and gas reserves. The Tangu Depression, particularly the Madong buried hill belt in the southwest block of the Tarim Basin, is recognised for its abundant oil and gas resources. However, the Madong structural belt underwent multiple tectonic movements, resulting in extremely complex structural conditions in the basin. The reservoirs in this area are buried deep, reaching depths of more than 6000m on average and are subjected to high temperatures and ultra-high pressure. As a result, this area faces complex wellbore stability issues during exploration and development. In the initial stages of development, due to an unclear understanding of the lithological characteristics and structural stress in the area, complex problems such as well wall collapse, drag, and pipe sticking were common during the drilling process(Zhang & Chen, 2022).
Numerical Analysis of Dynamic Instability of Juncture in Multilateral Drilling Based on Chemo-Mechanical Coupling
Authors: Xie Renjun , Yang Qiqi , Chen Xuyue , Yin Zhiming , Zhang Tianwei , Wang Gan , Liu Nanxiang 
Published: September 2023

ABSTRACT
During the drilling of multilateral wells in oil and gas fields, the juncture in multilateral drilling is a high risk area for collapse. Studying the factors affecting the stability of the multilateral well juncture is helpful to improve the success rate of sidetracking in branch wells. In this paper, based on the experiment, the variation law of shale rock mechanical parameters before and after drilling fluid immersion is obtained. The three-dimensional model of the juncture of multilateral drilling considering the decrease of rock strength under the action of hydration is established. The angle of the main branch well and the borehole azimuth angle of the main branch well on the stability of the multilateral well juncture is analyzed. The three-dimensional Coulomb failure criterion is introduced to characterize the dynamic failure of the rock, and the failure range and failure length of the multilateral well juncture under different conditions are obtained. The results show that the smaller the angle, the more obvious the stress concentration and the longer the failure length; the smaller the azimuth, the more stable the multilateral well juncture; with the increase of drilling time, the failure range of the multilateral well juncture is gradually expanding, and after 2d, the hydration effect gradually slows down. The model can simulate the influence of different conditions on the failure range and failure length of sidetrack multilateral well juncture, and has certain guiding significance for improving the success rate of sidetrack drilling and increasing production efficiency.

INTRODUCTION
After continuous production in oil and gas fields, production well output decreases and some production wells may even break down leading to scrapping or shutdown, and these conditions are a common problem in the middle and late stages of oil and gas field development. If new wells- are deployed, a significant increase in economic investment is required. However, if these low-producing wells, faulty wells, and shut-in wells are transformed into an optimized new well that can be reused in the original well network, the drilling cost will be greatly reduced and old wells will be revived, dead wells will be revived, and oil fields will gain increased production (Zhu et al, 2011). Lateral drilling branch well technology is to make full use of the old well network and the re-usable well section in the upper part of the old well to drill a new borehole that can reach the target layer and be used again. Lateral drilling branch wells are widely utilized because they have the characteristics of less time, low cost, increased oil absorption area and higher recovery rate (Sun et al, 2018 and Chen et al,2022). It provides economic development and relieves energy tension.