bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Study on the Evolution Law of Breakthrough Pressure of Mudstone Cap Under Alternating Load
Authors: He Aiguo , Ma Qingyuan , Pang Yuhan , Zhang Xujia , Yin Guojun , Lu Yunhu , Xu Nan , Guan Yueyang 
Published: September 2023

ABSTRACT
Breakthrough pressure, as an index to measure the sealing capacity of cap capillary, has always been the focus of gas storage seal integrity research. In this paper, using the method of SY-T5778-2013 to measure the rock gas breakthrough pressure, a breakthrough pressure test was carried out on the rock samples from the cover of the hydrogen storage reservoir of Well Jintanmao 17, and the influence law of the alternate load, porosity, permeability and breakthrough gas on the breakthrough pressure was analyzed. The results show that: (1) the breakthrough pressure of rock is mainly controlled by the permeability and other parameters, and the permeability is negatively correlated with the breakthrough pressure;(2) The alternating load before the yield point increases the core breakthrough pressure, and the alternating load after the yield point causes the core breakthrough pressure to decrease;(3) The air breakthrough pressure of mudstone is greater than the helium breakthrough pressure under the same conditions. The research results have guiding significance for comprehensive evaluation of gas storage cap bed dynamics.

INTRODUCTION
Different from foreign salt cavern gas reservoir construction in salt dome (salt layer thickness up to 300-500m), domestic rock salt resources are mainly layered rock salt containing interlayers, with poor grade (salt insoluble content in most salt mines is more than 30%), thin salt layer (60-250m), burial depth (more than 2000m in Pingdingshan and Chuzhou), etc. This kind of salt layer with a large number of interlayers is prone to instability of cap layer, weakening of seal property of salt layer and reduction of breakthrough pressure under alternating load, which greatly affects the sealing integrity of salt cavern storage and long-term stable operation of the storage (Han et al, 2006; Ozarslan et al, 2012; Wang J et al, 2019; Zhang et al, 2017; Bérest et al, 2003).
The integrity of the cap layer is essential for the safe storage and recovery of hydrogen storage in salt cavern. The cap layer of hydrogen storage should have a high capillary displacement pressure to prevent hydrogen percolation and diffusion. Breakthrough pressure is the most fundamental and direct evaluation parameter that reflects the sealing ability of cap layer (Deng et al, 2000).
Shearing and Opening of a Pre-Existing Discontinuity in Response to Fluid Injection
Authors: Lecampion B. , Sáez A. , Gupta A. 
Published: September 2023

ABSTRACT
We investigate the fluid-driven growth ofa shear crack along a frictional discontinuity and its transition to hydraulic fracturing (sometimes referred to as hydraulic jacking) under plane-strain conditions. We focus on the case of a constant friction coefficient and account for the permeability changes associated with the fracture opening. By combining the scaling analysis and numerical simulations, we examine the evolution of both the shear and opening fronts as a function of the hydro-mechanical properties of the pre-existing discontinuity, in-situ stress state, and the fluid injection conditions. Further, we derive an approximate analytical solution for the relation between the positions of the slip and opening fronts at large times. We notably show that the ratio between the slip and opening fronts converges to a constant value at late times which only depends on the ratio between the shear stress and shear strength acting initially along the discontinuity. We compare this approximate solution against numerical simulations and demonstrate its usage to serve as a benchmark solution in the development of coupled hydro-mechanical numerical solvers for frictional fluid-driven fractures.

INTRODUCTION
Hydraulic stimulation of pre-existing fractures is used in the geothermal development in order to increase reservoir permeability and achieve economical flow rates - with mixed success (Jung, 2013; McClure and Horne, 2014). Although the primary idea is to shear dilate these pre-existing discontinuities via injection, in a number of field tests (Guglielmi et al., 2020), a large increase of permeability is only observed when fracture opening has been reached (sometimes denoted as hydraulic jacking). Shearing of pre-existing discontinuities can also occur during more traditional hydraulic fracturing operations in oil and gas reservoirs, either by direct fluid pressurization or via stress transfer from the main fractures. In this contribution, we investigate the fluid-driven growth of a shear crack along a frictional discontinuity and its transition to hydraulic fracturing. We focus on the case of a constant friction coefficient and account for permeability changes associated with fracture opening. We use a fully coupled implicit numerical scheme for the solution of this non-linear hydro-mechanical problem. Notably, the frictional interface behavior is modeled using an elastoplastic constitutive relation with a non-associated flow rule.
A Review and Comparison of Coupling Strategies for Modeling Fluid Flow and Geomechanics
Authors: Quevedo R. , Roehl D. M. 
Published: September 2023

ABSTRACT
Coupled hydro-geomechanical processes in the oil and gas industry are usually simulated through the one-way strategy considering only the impact of fluid flow on geomechanics. However, depending on field and operation conditions, geomechanics can also affect the fluid flow. For those cases, more robust and accurate strategies must be adopted. Unfortunately, they require substantial computational effort and are time-consuming. This study reviews the coupling strategies for hydro-geomechanical problems and presents some algorithms that significantly improve their performance and stability. The fully-implicit, the two-way iterative, the two-way explicit, and the one-way strategies are implemented in an in-house framework to make fair comparisons among their results. Some numerical tests are performed considering several field conditions, such as heterogeneous rock properties and different geometrical settings between the reservoir and the surrounding rocks. The accuracy, stability, and required computational effort in each coupling strategy are discussed. The study shows that depending on the coupling level, one or another approach can be advantageous, producing accurate and fast solutions. The paper discussions can orientate in selecting adequate coupling strategies for engineering problems.

INTRODUCTION
Hydro-geomechanical processes in porous media are governed by two equations: mass balance and equilibrium of forces. As those equations are mutually dependent, a natural solution consists in solving them through a single system of coupled equations. This monolithic or fully-implicit strategy has been successfully applied in conceptual models (Sheng et al., 2003; Quevedo & Romanel, 2008; Huang et al., 2015; Mejia et al., 2019). However, due to high computational costs or ill-conditioned systems, the nonlinear behavior of porous materials may make the full-implicit approach unfeasible for large-scale applications.
Alternatively, sequential strategies have been used to link flow and geomechanics analysis codes by exchanging coupling terms. Such splitting in the solution raises the possibility of using different simulators to take advantage of the most appropriate solution methods. For example, different spatial discretizations can be adopted for reservoir flow modeling (limited to the reservoir region) and geomechanical modeling (including the reservoir and surrounding rocks).
The Effect of Graphite and Olive Waste on the Rheological and Filtration Properties of Saudi Class G Cement
Authors: Pratama Muhammad Andiva , Mahmoud Ahmed Abdulhamid , Elkatatny Salaheldin 
Published: September 2023

ABSTRACT
Cementing process is one of the most crucial parts of the drilling operation that could determine the durability and the stability of the oil or gas wells. Many additives had been introduced into the formula of the oil well cement to reach certain quality to support the well. "Greener" materials, such as olive waste, which is waste from the olive oil extraction process, have a huge potential to be utilized in well cementing to reduce the waste material in the environment. This study aims to analyze the effect of olive waste and graphite material on the rheological and filtration properties, compressive strength, and permeability of the cement sheath. Three different formulas of cement, base, graphite-based, and olive waste-based cement were used in this study. The result showed that the graphite and olive waste successfully increased the compressive strength by 106% and 110%, compared to the base cement, respectively. They also decreased the cement permeability as compared with the base samples. Although it increased the plastic viscosity and decreased the yield point of the cement slurry, the incorporation of olive waste into the cement slurry significantly decreased the water filtration.

INTRODUCTION
Oil well cement is the most important component for keeping the well stable and preventing the formation fluid leakage (Lavrov and Torsæter, 2016). However, making an ideal cement sheath in the annulus between the casing and the drilled formation is highly expensive with the materials that are present in the industry right now (Mitchell and Miska, 2011). Many researchers conducted studies to determine the best materials to be utilized to improve the oil well cement properties and reduce the cost of the cementing process while minimizing the need for remedial operations (Mahmoud et al., 2018a; 2018b; Ahmed et al., 2019; 2020a; 2020b; 2023; Mahmoud and Elkatatny, 2019; 2020a; Chen et al, 2022).
The environmental issue is one kind of problem that the industry needs to solve. Finding a much "greener" additive and process that provides high-quality cement is one thing that needs to find. Ridha and Yerikania (2015) have developed a Nano-SiO2 Geopolymer cement that provides as good, even better compressive strength than the conventional Class G cement under High-Pressure High Temperature (HPHT) conditions.
The Effect of the Olive Waste on the Rheological Properties, Thickening Time, Permeability, and Strength of Oil Well Cement
Authors: Ali Ahmed , Mahmoud Ahmed Abdulhamid , Al Ramadan Mustafa , Elkatatny Salaheldin 
Published: September 2023

ABSTRACT
In the oil and gas industry, cementing is a very important process to maintain the stability of the well. The cement slurry is injected downhole to fit the annulus between the casing and formation which in further can perform as an effective plug against fluids movement and at the same time supports the casing. In the design of the cement slurry, different types of additives are used based on operation conditions, incorporation of a new additive considerably affects all properties of the cement slurry and the solidified sheath. In this work, lab experiments were performed to investigate the effect of olive waste on Saudi Class G cement properties, the possibility of replacing the commercial retarder with olive waste was also studied in this work. Five samples with different olive waste content were prepared, and the rheological characteristics, thickening time, mechanical properties, and permeability of the samples were evaluated after 24 hours of curing at 95 °C. The results indicated that olive waste was able to replace the use of a commercial retarder. The addition of olive waste did not affect the cement plastic viscosity, while the yield point, 10-sec and 10-min gel strength of the cement were considerably increased with the increase in the olive waste content. The cement compressive strength was also increased with the incorporation of olive waste of a maximum of 0.375 %, and the permeability was decreasing with the addition of a maximum of 0.25 % olive waste.

INTRODUCTION
In the oil & gas industry, well cementing is an important operation to maintain the stability of the wellbore during drilling operations or production periods. In the cementing process, cement is pumped down the wellbore to fill the annulus between the casing and borehole (Adams & Charrier, 1985; Mitchell, 2006; Nelson & Guillot, 2006a; Hossain & Al-Majed, 2015). This cement can play significant roles and is used to achieve many functions such as providing a barrier between the formation and the wellbore, preventing fluid migration, and supporting the well casing (Al Ramadan et al., 2019, 2021; Fakoya & Shah, 2017; Jorge & Sampaio, 2007).
Numerical Investigation on the Impact of Drift Geometry Representation on the Assessment of Wedge Formation Using DFN Modelling in Underground Hard Rock Mines
Authors: Durham C. , Grenon M. , Karampinos E. , Dorion J. F. 
Published: September 2023

ABSTRACT
Geological discontinuities have a large impact on the rock mass behavior in underground excavations. Under low stress conditions, structurally controlled wedge failure is one of the most critical types of rock instability. The stability analysis, in this case, is essential to consider both the rock mass fracture network and the geometry of the opening. However, current wedge stability analysis tools do not typically examine the detailed geometrical characteristics of the rock discontinuities and the excavation shape in 3D. This paper reports on the development of a comprehensive and more rational numerical approach to assess wedge formation around underground mine openings. The approach considers the structural rock mass complexity using Discrete Fracture Network (DFN) modelling and the detailed 3D underground excavation profile obtained from surveying. The developed methodology was successfully applied to estimate the formation of wedges around an excavation in an underground mine. A detailed investigation on the 3D profile and shape of the excavation indicated that an oversimplification of the excavation geometry in the stability analysis can result in inadequate assessment of wedge formation. Further analysis allowed to identify elongated wedges that may not be critical from a stability perspective and wedges that were not entirely formed in the DFN model but may still be critical for the stability of the excavation.

INTRODUCTION
Under low-stress conditions, the stability of mining excavations is frequently controlled by rock discontinuities (Hoek et al., 2000). Wedges are formed by the intersection of more than two discontinuities on the walls of an underground opening. The structurally defined rock blocks can fall or slide toward the excavation. The most common wedges in the field are tetrahedral blocks defined by the intersection of three fractures and the surface of the underground opening (Windsor, 1999). Under these conditions, analyzing the size distribution and probability of occurrence of wedges is critical for the design and support of underground excavations.
Elongated Hydraulic Fracture Emerging from Layers of Alternating Fracture Toughness
Authors: Peruzzo C. , Lecampion B. 
Published: September 2023

ABSTRACT
Whether used to enhance the hydrocarbon production from low permeability rocks or to measure the minimum in-situ principal stress in rock formations, height growth of a hydraulic fracture above the formation of interest is a key metric for the design of successful hydraulic fracture applications. If the confining stress variation between rock layers represents one of the main reasons for fracture containment at depth, a contrast of fracture toughness can also lead to fracture containment. Fracture toughness contrasts are presents at different scales. They are due to lithological changes at the scale of layers, but they also appear at smaller scales, down to the size of bedding planes. The interaction of a hydraulic fracture with a repetitive sequence of multiple layers of different fracture toughness can ultimately lead to the emergence of an elongated fracture or, alternatively, to the propagation of an elliptical-like fracture with a fixed aspect ratio. Combining theory and simulations, we study the possible emergence of an elongated hydraulic fracture from layers of alternating fracture toughness considering typical hydraulic fracturing treatments as well as micro-hydraulic fracturing test cases.

INTRODUCTION
Hydraulic fracturing is an industrial technology in which a viscous fluid is deliberately injected into a solid to initiate and propagate one or more tensile fractures. This technology is successfully applied to measure the in-situ minimum stress in rock formations (Desroches and Thiercelin, 1993), but also to enhance the hydrocarbon production from low permeability rocks (Economides and Nolte, 2000). These rocks, usually referred as unconventional hydrocarbon reservoirs, are primarily located in sedimentary basins at depths ranging from one to few kilometers. In these basins the in-situ minimum stress is usually directed horizontally causing the hydraulic fracture to propagate on vertical plane and to interact with layer-like heterogeneities. To varying degrees, these heterogeneities comprise differences in the in-situ minimum stress, fracture energy, elastic properties, and leak-off-related quantities. Understanding their effect on the vertical hydraulic fracture growth, above the formation of interest, is of primary importance for the design of a successful hydraulic fracturing application (Bunger and Lecampion, 2017).
Assessing the Viability of Oilwell Cement for Underground Hydrogen Storage
Authors: Hussain A. , Emadi H. , Thiyagarajan S. R. , Ispas I. , Watson M. , Leggett S. E. 
Published: September 2023

ABSTRACT
Encouraging the use of renewable energy is crucial for meeting our energy needs, but it requires bulk storage to be practical. One potential solution is underground hydrogen storage, which could provide a consistent supply of clean energy for the world. Depleted hydrocarbon reservoirs may be a viable storage option for this purpose, given their existing infrastructure. However, ensuring wellbore integrity is a major challenge when storing hydrogen in such reservoirs. To test the feasibility of this approach, a core holder to replicate wellbore conditions having a 12" long, 4" diameter core sample that has a concentric two-inch drilled hole is used in this study. A one-inch perforated pipe, as the casing, is placed inside the 2" hole, and the cement will be placed between the pipe and the core. 72 hours after pouring the cement between the core and the pipe, hydrogen is injected into the sandstone from the casing through the cement. A CT scanner was then used to detect any leakage channels or cracks in the cement that could compromise the integrity of the storage system. One end of the cemented annulus is connected to a Data Acquisition system via transducers to detect any leakage. This new method could offer a promising alternative for underground hydrogen storage in depleted hydrocarbon reservoirs to detect leakage and ensure well integrity.

INTRODUCTION
Hydrogen is seen as a key element in the energy transition towards a more sustainable and low-carbon future as it is a clean energy carrier which makes it an ideal fuel for a low-carbon energy system. Hydrogen can be used in a wide range of applications, including transportation, electricity generation, heating, and industrial processes. The production of hydrogen using renewable energy sources, such as solar or wind power, can help decarbonize the energy system. In addition, hydrogen can be used to replace fossil fuels in a wide range of applications, including transportation and industrial processes (Bechara et al., 2022).
Hydrogen can be stored for long periods of time, making it an important energy storage medium for intermittent renewable energy sources like solar and wind power. This can help balance the grid and ensure that energy is available when it is needed (Canbaz et al., 2021). Salt caverns, aquifers, and depleted hydrocarbon reservoirs can be used to store large quantities of hydrogen for a long period of time. Depleted hydrocarbon reservoirs are the most suited as hydrogen can be produced and transported in a similar way to natural gas, and existing gas infrastructure can be repurposed for hydrogen use. This could help speed up the adoption of hydrogen as an energy carrier, as it can be distributed through existing pipelines and infrastructure (Al-Hadrami et al., 2022).
Slope Stability Analysis and Design for Small-Scale Mines
Authors: Mgiba C. , Rupprecht S. M. 
Published: September 2023

ABSTRACT

Introduction:
Artisanal and small-scale mining (ASM) is the extraction of ore with minimal to no mechanization by individuals or group of people who do not have advanced technical knowledge. Though ASM has gained considerable acceptance, one reason for its unsustainable is because of slope collapses that occur affecting the health and safety of miners and surrounding community. In rock mechanics, slope stability analysis and design has received significant attention in large scale mining to mitigate the risk of slope collapse but minimal implementation in artisanal and small-scale mining. This paper reports back the implementation of slope analysis and design through field observations to demonstrate the process of estimating rock mass rating (RMR) and finding suitable slope angles using Bieniawski (1976) RMR and Heins and Terbrugge stability charts respectively. Further analysis through laboratory strength tests and using numerical modelling software to assess the slope stability of the current and proposed slope design was conducted.

Results:
The slope design used in the ASM operation is unsuitable and the slope analysis using estimation charts required further analysis. Rock strength results were then used in OPTUM G2 to attempt to imitate reality. Suggested mining methods were proposed and mapped in OPTUM G2 where the limit equilibrium analysis showed that the gravity multiplier had increased by 10.04 for the upper limit and 2.79 for the lower limit and the strength reduction factor increased by 1.5.

Significance:
It is essential to continuously refine critical issues and help establish desirable conditions for ASM operations because it has a high potential to contribute towards sustainable development. Implementing cost-effective slope stability analysis systems for sustainable mining and promote achieving Sustainable Development Goal 1,3,8 and 9.

Conclusion:
The estimation process can be used with the guidance of a rock engineering practitioner during the design process of the mine after exposing the rock mass during the exploration stage. However, there may be other factors that can hinder the collection of data and modelling during the design phase as slope stability analysis systems were designed for large-scale mines.