bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sediment Stress in an Extensional Basin with Pre-Existing Fault and Salt Roller
Authors: Nikolinakou M. A. , Heidari M. , Hudec M. R. , Flemings P. B. 
Published: September 2022

ABSTRACT:
We study sediment stress in an extensional basin with a critically oriented pre-existing fault and an underlying salt layer using forward geomechanical models. We first identify stress changes in a basin without salt. We show that the presence of a fault with lower frictional resistance than the intact sediment leads to re-orientation of principal stresses near the fault, and abrupt changes in the minimum principal stress across the fault. Sediment rollover in the hanging wall leads to stress arching, which reorients principal stresses in the upper parts of the hanging wall despite the ongoing extension. When salt underlies the sediment basin, a salt roller develops at the location of the fault and minimizes sediment rollover in the hanging wall. Loading from the rising diapir increases horizontal stress in the hanging wall. The angled salt face also transmits higher overburden stresses from deeper parts of the basin to the shallow footwall area and loads the footwall sediments. We built these transient evolutionary simulations with Elfen. We model salt as solid viscoplastic and model sediments as poro-elastoplastic material.

1. INTRODUCTION
Several numerical studies have explored the geomechanical interaction between salt and its wall-rock sediments (see Nikolinakou et al. (2018) for a review). These studies couple salt flow with sediment deformation and, in transient analyses, porous fluid flow. However, they model sediments as a continuum.
A large number of salt basins are located in extensional systems (rift basins, passive margins; e.g., Jackson and Hudec (2017)). Normal faults are key features in these extensional systems. Faults are often weak discontinuities: their frictional strength is lower than that of continuum sediments. They can alter the in-situ stress state, sediment porosity, and strength (e.g., Schultz (2019)). Consequently, they may affect the salt flow and evolution of the salt geometry.
Here, we study a simple extensional basin with a pre-existing fault and an underlying salt layer. We use a large-strain, evolutionary model to simulate the regional extension, the development of a salt diapir, and the deformation along the critically oriented fault. We first identify stress changes in a basin without salt. Then, we study how the presence of a reactive diapir affects the stress state in both hanging wall and footwall.
Undrained Creep Response of Shale: Argon vs. scCO2
Authors: Kamali-Asl A. , Hashemi S. S. , Kovscek A. R. , Zoback M. D. 
Published: September 2022

ABSTRACT:
We used core samples from the Wolfcamp formation in the Permian Basin to conduct creep experiments with argon and scCO2 as the pore fluids. We conducted the tests at a temperature of ~ 42 °C, confining pressures of 40 and 70 MPa, pore pressures of 10 MPa, and various levels of differential stress. Creep stages lasted for either 24 or 48 hours and prior to creep the Young’s modulus was estimated based on the loading history. When CO2 results are compared to the argon results, the Young’s modulus of the carbonate-rich sample increases, while the Young’s modulus of the clay-rich sample decreases. The viscoplastic response with scCO2 as the pore fluid generally indicates more significant deformation. This is attributed to the aggregate effects of carbonate dissolution and swelling strain of clays and kerogen. A power-law model has been implemented to predict the longer-term creep response of the samples. The fitting parameters are satisfactory; however, additional investigation is needed for the scCO2 case, due to time-dependent chemical interactions with the sample.

1. INTRODUCTION
Geological storage of carbon dioxide (GCS) is one of the relatively short-term feasible solutions to climate change (Bouckaert et al., 2021). While the storage of CO2 is likely to occur in a porous sandstone reservoir, the target formation needs to be sealed by a low permeability caprock such as shale. Employing CO2 as the stimulation fluid of unconventional reservoirs is another method of sequestering carbon dioxide into the subsurface. In both applications, the shale formation is exposed to CO2 over prolonged periods of time. Therefore, it is necessary to investigate the alterations in the mechanical/transport characteristics of shale reservoirs when they are exposed/interacted to/with CO2.
Shales typically possess ultra-low permeabilities (usually below 1 μD) with very complex micro-structure, and is mainly composed of quartz, carbonates, clays, and organic matter (Zoback and Kohli, 2019). Interaction between shales and carbon dioxide in the presence of in-situ water results in (i) adsorption-induced swelling of clays and organic matter, (ii) dissolution of carbonate minerals due to interaction with carbonic acid, and (iii) mineral/salt precipitation (Linder et al., 2016; Kamali-Asl et al., 2021). Some past research has been dedicated to the changes in the micro-structure of shales as they are exposed to dry CO2 or CO2-saturated brine (Sanguinito et al., 2018; Hadian and Rezaee, 2020), while others have focused on changes of porosity/permeability (Wu et al., 2017; van Noort and Yarushina, 2019).
Numerical Analysis of Interaction Between Hydraulic Fracture and a 3D Spherical Cave
Authors: Kao Jiawei , Xu Dan , Bian Xiaobing , Yin Shize , Jin Yan 
Published: September 2022

ABSTRACT:
The matrix is dense for deep cavernous carbonate reservoirs in Tarim Basin, and oil and gas are mainly enriched in caves. We hope that hydraulic fractures can communicate with more caves. However, the existence of caves will disturb the stress field and influence hydraulic fracture propagation. Thus, the interaction between hydraulic fractures and caves and whether they can penetrate caves has a significant impact on the fracturing efficiency of cavernous formation, which is worth studying.
This paper studied the interaction rule between hydraulic fracture and a 3D single cave by discontinuous discrete fracture model (DDFM). In this model, the cave was set as a three-dimensional sphere with fluid in it, which is located in the maximum horizontal stress direction along one side of the vertical well. The initial hydraulic fracture is perpendicular to the direction of minimum horizontal stress. The fluid-solid couple action, fluid flow, and mass transfer during fracturing were considered. By means of the control variable method, we analyzed the intersection characteristic between hydraulic fracture and a cave and whether it could be penetrated.
The results show that when hydraulic fracture approached close to a cave, it expanded to the side of the cave preferentially due to an attraction action. After they intersected, hydraulic fracture turned to expand along height direction at the intersection to break the cave wall because of stress concentration. However, they encountered resistance when hydraulic fracture opened most of the cave wall and tried to penetrate. Under limited injection volume conditions, whether hydraulic fracture can penetrate and continue to expand was related to cave diameter, in-situ stress, the distance between the cave and well, filtration coefficient, and injection rate.
This paper revealed the propagation characteristics and morphology of hydraulic fracture interacting with a 3D cave, which could help understand the interaction between hydraulic fracture and a 3D cave and provided a reference for optimizing the fracturing parameters of cavernous carbonate reservoirs.
Permeability of Water-Rich Sandstone Experienced One Freeze-Thaw Process Under Different Confining Pressures
Authors: Liu Bo , Yang Shuo , Zhang Jingtao , Han Yanhui , Sun Yanding , Zhang Xianxin , Liu Nian 
Published: September 2022

ABSTRACT:
During the construction of mine shafts in Northwest China, the rock mass in frozen wall experiences a full cycle of freeze-thaw loading process, which will lead to the change of porosity and permeability of rock mass. Due to the lack of in-depth understanding of the permeability of rock mass after thawing, water penetration and shaft flooding accidents have occurred frequently. In this study, the permeability characteristics of sandstone samples without freezing-thawing and experienced one freeze-thaw cycle under different confining pressures were investigated. The effects of the confining pressure in the freeze-thaw loading process (referred to as freeze-thaw stress), osmotic pressure and effective confining stress (i.e. the confining pressure minus osmotic pressure) on the permeability of the sample were also analyzed. The results indicated that the permeability of the sample increased along with the osmotic pressure when the osmotic pressure was less than 5 MPa. However, when the osmotic pressure was greater than 5 MPa, the permeability tended to be stable as the osmotic pressure increased, and decreased slightly for some samples. The permeability of sandstone samples undergoing freeze-thaw process decreased with the increase of effective confining stress. When the osmotic pressure was constant, the permeability increased linearly with freeze-thaw stress. CT test results showed that the porosity increased after freeze-thaw test, resulting in an increase of permeability with the increase of freeze-thaw stress. The experimental results are helpful for the pre-control of water intrusion related disasters occurring after the thawing of the frozen wall.

1. INTRODUCTION
Mine shaft construction in Northwest China mainly cuts through the Jurassic and Cretaceous strata characterized as weakly cemented and water-rich strata. Artificial freezing is the main effective technology to excavate the deep water-rich strata in mining. However, due to the lack of understanding of the permeability characteristics of the frozen wall after thawing, water penetration and shaft flooding accidents have occurred frequently. (Zheng et al., 2011; Deng et al., 2010).
The LOP Revisited
Authors: Raaen A. M. , Andrews J. S. , Fintland T. G. 
Published: September 2022

ABSTRACT:
The Extended leak-off test, XLOT, is a main tool for obtaining minimum stress data during drilling operations. If performed according to a proper protocol, it is perhaps the most cost-effective and robust method for determining the minimum stress. The low cost of the test means that a lot of data can be collected, allowing for efficient regional analysis. A widely reproduced figure by Gaarenstrom et al. (1993) has become a classic in the industry. It shows the pump-in phase as two distinct linear segments. The point of change in slope is denoted the Leak-off Point or the Leak-off Pressure (LOP). It is sometimes argued that the LOP is a good measure of the in-situ stress, and it is sometimes argued the LOP marks the initiation of a fracture. We analyze this hypothesis and show by basic theoretical considerations and several examples of high quality field data that this is not necessarily the case. The nonlinear behavior during initial pump-in may be due to leak-off to a permeable formation or through a poorly cemented casing shoe.

1. INTRODUCTION
The importance of knowing the in-situ stress has been realized for a long time in the petroleum industry, see e.g., Hubbert and Willis (1957), Fairhurst (1965), Haimson and Fairhurst (1967), Nolte and Smith (1981), and many others.
The minimum stress is of direct use in hydraulic fracturing, where proper stress data are essential for the design of a successful job. Therefore, most conventional fracturing jobs are preceded with datafracs or minifracs, aiming to determine the parameters for designing the main job, with the minimum horizontal stress being of central importance in addition to calibrating fluid leak-off behavior during fracture propagation. More recently the Diagnostic Fracture Injection Test has gained prominence in very tight and unconventional plays where it is possible to estimate the same main parameters but also analyze for pore pressure and permeability.
Research and Application of Integrated Technology of Chemical Sand Control and Stratified Water Injection in Offshore Oilfields Injection Well
Authors: Shunchao Zhao , Yugang Zhou , Huaxiao Wu , Baobing Shang , Tao Fang , Huaxing Chen , Yufei Wang , Yadong Qi , Ming Pang 
Published: September 2022

ABSTRACT:
This paper proposes an integrated technology of chemical sand control and stratified water injection in water injection well, which enlarge the inner diameter of injection well and achieve flexible stratification. The technology realizes completion by chemical sand control. The ceramsite whose surface has been treated by crosslinking agent is injected into the well and form a cement layer with a thickness of 3-5 cm. This layer can be used as a barrier to retain sand and provide channels for fluids. Then, the stratified injection string is run to realize the stratification of the injection reservoir. The position and quantity of the stratification are designed can adjust flexibly. This technology has been successfully applied in the Bohai Oilfield. The conventional sand control and injection technology makes it difficult for the actual injection rate to reach the target value. After applying the integrated technology, for a directional well with a bore diameter of 9.625 in, the maximum inner diameter can reach 7 in. The number of injection layers exceeds 5, and the actual injection volume meets the designed rate. Besides, the water cut of the beneficiary well decreases, and the oil production rate increases.

1. INTRODUCTION
Stratified water injection is an important measure to improve the overall oil recovery, and it is very important to achieve sufficient water injection in the target reservoir. The sand control method of water injection wells in offshore oilfields is mainly mechanical sand control. The plug-in seal on the water injection pipe cooperates with the sealing cylinder to realize stratified water injection, which the number of layers is generally 3-4. For reservoirs with strong vertical heterogeneity, there may be problems such as large differences in water absorption profiles in the same injection layer, small longitudinal sweep coefficient of water flooding, and overall water injection rate that does not meet the design requirements. It is difficult to change the number and the location of layers, and it is impossible to adjust the layers according to the water injection system. In addition, the inner diameter of mechanical sand control is small, and the downhole testing and other operations are difficult, which also limits the injection rate.
A Prediction Model of Casing Exterior Wear During Casing Running
Authors: Zhou Yuting , Zhang Hui , Li Jun , Lu Zongyu , Shi Jiangang 
Published: September 2022

ABSTRACT:
In the process of exploration and development of extended-reach wells and ultra-deep wells, serious dogleg severity and high hardness formation, etc. will lead to casing exterior wear, thereby reducing the residual strength of the casing. However, the existing research on casing wear mainly studies the interior wear of casing caused by the rotation of drill pipe joints, and ignores the exterior wear caused by the contact between casing and well wall during casing running. As a consequence, the prediction model of casing exterior wear is established based on the wear efficiency model and the three-dimensional torque and drag model. Case study is conducted with this model and sensitivity analysis is also performed. The results show that the casing with the greatest exterior wear depth is located below the direction turning section. The wear depth decreases with the increase of the outer radius of the casing, and increases with the increase of the wellbore radius. In addition, with the increase of drilling fluid density, the wear depth of the upper casing increases, and the wear depth of the lower casing decreases. The casing collapse resistance after casing exterior wear is studied through numerical simulation. The results show that the collapse resistance of casing decreases with the increase of wear depth, and there is an approximate linear relationship between the two. The study provides a method to improve the prediction accuracy of casing wear, which is of great significance for the casing design and wellbore integrity.

1. INTRODUCTION
With the development of drilling technology, horizontal well and extended reach technologies are widely used in the world. The wellbore conditions of extended-reach wells and horizontal wells with long horizontal sections are more complicated than conventional wells. Running casing is challenging due to the difficulty of hole cleaning, the high friction factor, the wellbore tortuosity, and the large lateral force acting on the wellbore by the casing, etc. Usually the casing needs to be picked-up and released many times, and the running time is long, so the outer wall of the casing is more likely to be worn, which reduces the residual strength of the casing.
Experimental Study on High-Strength Resin Wellbore Annulus Plugging Technology of Underground Gas Storage Facilities
Authors: Leng Guangyao , Yan Wei , Ge Hongkui , Deng Jingen , Nguu Dickson Muchiri , Tan Rui , Han Yue , Li Zhong 
Published: September 2022

ABSTRACT:
Underground gas storage is characterized by large gas injection and withdrawal cycles, making the wellbore bear repeated loading and unloading. Subjecting cement sheath to these conditions can cause damage, thus compromising its ability to provide complete zonal isolation. Wellbore annulus plugging with high-strength resin technology was studied to evaluate its effectiveness in controlling unwanted fluid migration through triaxial mechanical properties test, corrosion inhibiting ability test, and anti-gas channeling performance evaluation. The experimental results showed that the curing time was extended by 1.9 hrs by doubling the amount of diluent. At the same time, doubling the amount of the curing agent increased the compressive strength by 5.3 MPa. Under the triaxial test conditions, the four resin materials exhibited high compressive strength, low elastic modulus, and low Poisson’s ratio. Injection of corrosive CO2 at 0.5 MPa, reduced the compressive strength of the four resins within the range of 4.9% ~24.3%. A 100g of epoxy resin mixed with 10 g of diluent and 20 g of the curing agent significantly reduced the curing time. In addition, this mixture increased the maximum differential stress, and elastic modulus to 100.5 MPa and 3.325 GPa, respectively, after 1.6 h. The gas test anti-channeling pressure of the 5 cm sample was as high as 19.1 MPa. The test samples maintained long-term stability under continuous high pressure and tightness under the action of the alternating load of a significant pressure difference. This study uses high-strength plugging gel technology to provide a technical guide for wellbore remedial redress and plugging in underground gas storage.

1. INTRODUCTION
The formation is effectively sealed with cement to prevent cross-flow under differential pressure and ensure smooth oil and gas production (Jordan et al., 2015; De et al., 2017; Hatambeigi et al., 2020; Valov et al., 2022). Cement has the disadvantages of high brittleness, poor corrosion resistance, and insufficient durability. Under the action of alternating load, micro-cracks and micro-annulus can easily be generated on the wellbore system. In addition, the presence of an acidic medium such as CO2 can cause the cement barrier to corrode, further compromising its ability to prevent unwanted fluid migration.
A Study of Progressive Failure in Porous Rocks Using Numerical and Experimental Modeling
Authors: Bianchi P. , Selvadurai P. A. , Vasquez A. Salazar , Dal Zilio L. , Gerya T. , Madonna C. , Wiemer S. 
Published: September 2022

ABSTRACT:
Physical mechanisms governing natural and induced earthquakes are still poorly understood and, despite the relevance, this lack of knowledge limits the usefulness of Geoenergy projects and severely undermines their societal acceptance. Due to the difficulty in retrieving direct measurements and observations to understand these important processes, we study laboratory acoustic emissions in combination with numerical models to shed light on the physics governing seismicity. A dry sample of Berea sandstone was tested to failure under a confining pressure of 40 MPa in a triaxial machine (LabQuake). Using in-house developed conical-type piezo-electric transducers, which are absolutely calibrated and exhibit a flat, broadband response between 100 kHz and 1.5 MHz, we are able to investigate the generated acoustic emission clouds by locating the single events and by inverting for their moment tensor solutions. Furthermore, numerical simulations are performed using a finite difference two-dimensional continuum-based fully coupled thermo-mechanical visco-elasto-plastic numerical modeling tool. We are able to image and locate regions of high stress and strain and, thus, to identify potential nucleation zones of seismic events and compare them at a first order with our experimental results.

1 INTRODUCTION
Many scientists and engineers are seeking strategies and alternatives to counteract climate changes. Among others, green energies are being investigated by the research community; Geoenergy related applications, such as enhanced geothermal systems (EGS), are thought to have a critical role (e.g., Scheck-Wenderoth et al., 2013; Lu, 2018; Wu and Li, 2020). However, the injection or extraction of fluids in the subsurface is a well-known cause of perturbation of the effective stress of a rock formation (e.g., Hubbert and Rubey, 1959), which may eventually lead to induced seismicity (Majer et al., 2007). In the last decades, various geothermal reservoir projects were the cause of some damaging earthquakes, which subsequently gave rise to the abandonment of such projects (e.g., Deichmann and Giardini, 2009; Grigoli et al., 2018). The societal acceptance of geothermal projects is thus severely influenced by such induced earthquakes (Trutnevyte and Wiemer, 2017; Grigoli et al., 2017) which, furthermore, are source of outstanding economic impact on the society (Mignan et al., 2015; Trutnevyte and Wiemer, 2017). Despite significant research efforts, the physical mechanisms governing induced seismicity are still not entirely understood and this lack of knowledge severely limits the potential of Geoenergy applications.