bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shear and Vertical Deformation Behaviour at the Field Scale During CO2 Storage in a Depleted Chalk Reservoir (Danish North Sea)
Authors: Amour F. , Hosseinzadehsadati S. B. , Hajiabadi M. R. , Nick H. M. 
Published: September 2023

ABSTRACT
CO2 storage represents one of the recommended remediation methods to reduce the emission of anthropogenic CO2 in the atmosphere. As part of the Bifrost project that aims at developing CO2 storage activities in Denmark, a series of coupled hydro-mechanical-chemical simulations is carried out in the Harald East chalk field to assess the flow and mechanical response of the storage site, assuming both continuous and intermittent injection. A total of two continuous injection scenarios during 16 years (scenario 1) and 32 years (scenario 2) and scenario 3 which assumes intermittent injection are considered. The injection rate in scenario 2 and 3 is half of that of scenario 1, and the duration of the injection in scenario 3 is increased compared to scenario 1. The rate and duration of injection are adjusted to ensure a similar volume of stored gas in each simulation run. The outcomes show that fast injection prevents significant compaction in the reservoir. Besides, the calculated shear deformation in the overburden is utilised to study wellbore stability during storage. The results indicate that the accurate characterisation of the porosity distribution in the reservoir as well as the potential mechanical weakening of chalk by CO2 are essential for reliable wellbore integrity analyses. Further studies will be conducted to assess wellbore stability in the Harald East area during CO2 storage activities.

INTRODUCTION
The capture and underground storage of anthropogenic CO2 (CCS) represent a valid technology that helps tackling climate change by reducing the amount of greenhouse gas emitted by our societies (Al Amer, 2022; ICPP, 2005). Using pre-existing infrastructures present in depleted hydrocarbon fields drastically reduces the cost associated with CCS activities compared to other sites e.g., onshore and offshore aquifers (Schmelz et al., 2020). Besides, the proven efficiency of the cap rock that contained hydrocarbon for millions of years and the current low formation pressure below hydrostatic conditions are limiting risks of leakage. Located offshore, CO2 can be either shipped to the storage site, such as planned for the Greensand project or transported by pipeline as planned for the Northern Lights project. Taking into account that the floating units used to temporary store CO2 transported by boats prior to injection have limited storage capacities, shipping gas can compel the stakeholders to carry out intermittent CO2 injection in case of bad weather conditions, workovers, and potential shortages in CO2 supplied by the industry.
FDEM Modeling on the Fracture Propagation Behavior of Hot Dry Rock Subjected to Cyclic Soft Fracturing
Authors: Wu Xiaoguang , Yang Rui , Li Gensheng , Huang Pengpeng , Huang Zhongwei , Liang Rui , Long Tengda 
Published: September 2023

ABSTRACT
Conventional hydraulic fracturing (HF) is an important way to develop Enhanced Geothermal Systems (EGS), but there are some problems such as high injection pressure and having trouble to create complex fracture network. To deal with those difficulties, Cyclic soft fracturing (CSF), an emerging technology, has been proposed, which adopts circulating stress waves to break down rock and forms a volumetric fracture network achieving oil and gas stimulation. In this paper, a numerical model of FDEM and a fully coupled thermal-fluid-solid solver are used to perform CSF experiments on hot dry rock (HDR) in field scale. The influences of stress disturbance, fracture initiation and propagation and three key parameters on fracture morphology are analyzed. The research results show that CSF can indeed generate complex fracture network under parameter optimization of peak pressure and loading frequency. Compared with conventional HF, CSF forms a larger stress disturbance area and has bigger tensile stress at fracture tip, which may contribute to fracture propagation. Under large stress difference condition, with the increase of peak pressure, the fracture complexity increases first and then decreases. The results are expected to provide an insight into the stimulation mechanisms of CSF method in HDR geothermal.

INTRODUCTION
Geothermal energy is a common renewable energy in the earth crust with the advantages of great potential resource, wide distribution and cleanliness (Wang, 2012). Hot dry rock (HDR), as a typical type of geothermal resources, offers great potential in meeting the growing demand for energy and achieving low-carbon solutions. Enhanced Geothermal Systems (EGS) is the main method for developing HDR geothermal energy. Hydraulic fracturing (HF) is the most important mean of EGS reservoir reconstruction, by which the production rate increases with stimulated reservoir volume created. Considering the special characteristics of HDR (e.g. high temperature, high hardness and high density), conventional HF has the problem of high injection pressure, low injection rate and the formation of simple fracture plane. Also, induced seismicity by HF has become one of the important limiting factors for the sustainable development of EGS engineering around the world (Li et al., 2022). In order to decrease breakdown pressure, mitigate seismicity and generate a complex fracture network, new stimulation strategies have been proposed, including fatigue hydraulic fracturing (Zang et al., 2013) and cyclic soft stimulation (Hofmann et al., 2018), which adopts fluid-injection protocols of displacement control and pressure control, respectively. A large number of experiments have proved that these methods are beneficial to solving the problems existing in the development of HDR (especially induced seismicity) caused by conventional HF stimulation (Hofmann et al., 2018; Zang et al., 2019; Zhuang et al., 2019).
Determination of Biot Coefficient for Low-Permeability Rocks Accounting for Undrained Loading
Authors: Kim Kiseok , Espinoza D. Nicolas 
Published: September 2023

ABSTRACT
The determination of poroelastic properties for low-permeability porous media (k &lt; 10−18 m2) is often elusive because of long periods required to dissipate or equilibrate pore pressure in tested samples. Poroelastic properties, such as the Biot coefficient, play a key role in determining the effective stresses in-situ and changes due to thermal, hydraulic and mechanical loadings. This paper presents a method to determine the Biot coefficient of low-permeability porous media accounting for undrained loading. We conducted experiments and numerical simulations to show the effectiveness of the method and ran parametric studies by changing the loading rate, equilibrium time, and permeability. The results show that the Biot coefficient, drained bulk modulus and permeability can be determined from a single partially undrained experiment as long as undrained response is considered in the data analysis. This method is advantageous not only because it is faster than previous methods but also because it can determine permeability indirectly. Accurate determination of these properties is critical to predict the response of low-permeability materials such as seal rocks for carbon geological storage among other applications.

INTRODUCTION
Accurately characterizing the poromechanical response of geological formations is critical for the success of subsurface energy projects, such as oil and gas recovery, geologic carbon and hydrogen storage, geothermal energy, and nuclear waste geological storage among others. Low permeability formations (k &lt; 10−18 m2) play a vital role in many cases as sealing layers or containment barriers. Low-permeability formations exhibit a strong hydromechanical coupling, hence, confidently predicting their poromechanical behavior is critical (Bachu 2008; Makhnenko et al. 2017; Espinoza and Santamarina 2017; Zheng et al. 2022). However, accurate measurement of poromechanical properties can be challenging for materials with ultra-low hydraulic diffusivity due to the long period needed to achieve pore pressure equilibrium when external loadings are applied (Kim and Makhnenko 2020).
Drilling Data Based Approach for Equivalent Circulation Density Prediction While Drilling
Authors: Abdelaal Ahmed , Elkatatny Salaheldin , Gamal Hany , Ziadat Wael 
Published: September 2023

ABSTRACT
The current research presents a machine learning application toward predicting the equivalent circulating density (ECD) in real-time while drilling operations. Maintaining high accuracy in estimating equivalent circulating density (ECD) is crucial due to the potential well control issues that can arise from inaccurate ECD values. Inaccurate ECD can lead to problems such as fluid losses, formation fracturing, kicks, and blowouts. Therefore, precise ECD estimation plays a vital role in preventing these issues and ensuring the safety and stability of drilling operations. The fourth industrial revolution provided high technology-based solutions to serve the oil and gas industry and machine learning is considered one of the best tools in research and development. The developed model within this study utilized the drilling hydraulic data in terms of initial mud weight, mud pumping standpipe pressure, and pumping rate to be fed to the random forest model to predict the ECD with good accuracy. A data set of 5,140 data points was used through a comprehensive data analytics workflow to enhance data quality that greatly impacted the model accuracy. The obtained results showed the outperformance of the developed model to predict ECD with a correlation coefficient (R) of 0.99 between the actual and predicted ECD data with a low mean square error of 0.04. The developed model will add more to the drilling automation process toward safe and efficient operations through providing high accurate ECD values while drilling.

INTRODUCTION
The drilling operations are considered the most critical among the other operations in the oil and gas due to safety precautions and well control issues that impact the personnel's life and the operations’ high cost. Monitoring the drilling operations with many sensors along the surface beside downhole sensors will help control the operations. Equivalent circulating density (ECD) is considered one of the parameters during drilling operations and should be given special care while drilling narrow window zones where there is not a wide gap between the pore and formation fracture pressures. ECD represents the hydrostatic pressure of the drilling mud and the annular friction pressure losses while circulating the wells (Haciislamoglu, 1994). Inaccurate estimation of ECD may lead to many well control issues as ECD might increase and cause mud losses or even fracturing the drilled formations, while low ECD value below the drilled zone pore pressure may result in a kick and flow from the drilled formations. Hence, many well control problems will be encountered with inappropriate ECD estimation. Many factors affect ECD such as hole geometry, pressure losses profile, drilling mud rheological characteristics especially mud weight and viscosity, well pressures and temperature profiles, and hole cleaning (Hemphill and Ravi, 2011; Zhang et al. 2013; Abdelgawad et al. 2019).
3D Pore-Scale Modeling of Mineral Dissolution and Precipitation in Fractured Rocks
Authors: Kang Q. , Liu M. , Carey J. W. , Viswanathan H. S. 
Published: September 2023

ABSTRACT
We present a pore-scale numerical modeling study of coupled fluid flow, solute transport, and mineral dissolution/precipitation in 3D fractured carbonate rocks. The injected fluid can dissolve the carbonate and release carbonate ions into the solutions, which react with Ba2+ resulting in barium carbonates (BaCO3) precipitation. Both a simplified fracture and a complex fracture geometry extracted from real shale images are considered. Simulations with a wide range of Pe and Da numbers are carried out to systematically study their effects on dissolution/precipitation patterns and on evolution of fracture geometry, porosity, and permeability. The results show that the coupled physicochemical process is strongly dependent on the Pe and Da. While similar trend of the permeability-porosity variations is obtained for the two fractures at the same Pe and Da numbers, the evolution of fracture morphology is different due to the difference in initial structure heterogeneity and wall roughness. This work reveals the interplay of advection, diffusion, and reaction in determining the fracture evolution and improves our understanding of fluid-mineral interactions in fractures.

INTRODUCTION
Fractures play an important role in providing preferred flow pathways in low-permeability formations and significantly enhance their permeability. They can improve gas production for shale reservoirs but can also increase the risks for leaking of CO2 from geological storage sites.
The fluid-mineral reactions, including dissolution or precipitation, can cause the alteration of porous medium matrix or fracture wall. Particularly, mineral dissolution (precipitation) can increase (decrease) the pore/aperture size and hence the permeability of porous or fractured media. While there have been a lot of studies on mineral dissolution in porous or fractured media considering resultant pore-structure change (Chen, Kang, Viswanathan, et al., 2014; Kang et al., 2014; Kang et al., 2002; Liu & Mostaghimi, 2017; Rasoulzadeh et al., 2020; Starchenko et al., 2016; Verberg & Ladd, 2002; Verhaeghe et al., 2005, 2006), studies on mineral precipitation are much less (Deng et al., 2021; Kang et al., 2005; Kang et al., 2003; Menefee et al., 2020), and studies on coupled dissolution and precipitation are scarce (Chen, Kang, Carey, et al., 2014; Kang et al., 2010). Particularly, there is no high-resolution pore-scale modeling study on coupled dissolution and precipitation in three-dimensional (3D) fractures with evolving fracture geometry to our best knowledge. Consequently, the complex coupled processes including fluid flow, solute transport, dissolution/precipitation, and evolution of pore structure are not well understood.
Coupled Pore Pressure and Geomechanical Modeling of a Naturally Fractured Reservoir
Authors: Yao Qiuliang , Madyarov Andrew 
Published: September 2023

ABSTRACT
Natural fractures play a significant role in oil and gas production by serving as the primary fluid pathways in reservoirs with low matrix permeability. However, their behavior is sensitive to stress change. The depletion of reservoir pressure will increase the effective stress and may cause natural fractures to close. Closure of opened fractures may create pressure barriers and impede further depletion. Numerical simulation of a naturally fractured reservoir remains challenging. A fully coupled finite element model is developed in this study using commercial finite element method (FEM) software. The interaction between total stress and reservoir pressure is computed using a Biot-Gassmann poroelastic model, and the depletion is modeled as pressure diffusion using Darcy's law. The closure of natural fractures is modeled by associating the permeability to stress using a subroutine that reads the stress at each time iteration to compute the corresponding permeability and update the material property at each material point. A scenario study successfully demonstrates the modification of the depletion pattern because of the closure of natural fractures.

INTRODUCTION
When natural fractures develop within a reservoir, geomechanical and hydraulic properties interact with one another (Davies & Davies, 2001). The initial spatial distribution of opened fractures has a significant impact on fluid flow and pressure depletion (Heffer et al., 1994). The in-situ stress field responds to reservoir pressure changes according to porous media constituting material laws. On the other hand, hydraulic properties of natural fractures are sensitive to stress conditions. Closure of opened fractures creates a pressure barrier and can impede further depletion. Such interactive behaviors are highly dynamic and should be modeled in a coupled manner (Jin et al., 2000). Most current modeling approaches involve two separate simulation platforms: (1) fluid flow and reservoir pressure modeled with reservoir simulators and (2) stress evolutions modeled using FEM simulators (Myers et al., 2017). Such approaches depend on a large amount of data repeatedly transferred between the two platforms. Recently lots of efforts of coupled modeling have been reported or implemented into commercial software. Generally, the reservoir simulator is the master or host in the coupled process, therefore the focus is on fluid simulation, but the stress is typically handled oversimplified. Furthermore, properly modeling the modification of fracture transport properties attributed to stress variations remains challenging (Gao & Gray, 2022).
Nanoindentation Characterization of Vaca Muerta Formation Shale Rocks and Its Relation to Geomechanical Model and Core Plugs Properties
Authors: Noya M. , Celleri H. , Camilion E. , Caneiro A. , Floridia A. , Grasetti C. G. , Ramallo J. I. , Fuertes M. C. 
Published: September 2023

ABSTRACT
Nanoindentation has arisen as a promising technique to geomechanically characterize small cutting samples obtained during drilling a well. This technique is a useful tool to characterize unconventional reservoirs during the exploration phase. While we have previously analyzed cutting rock samples from Palermo Aike Fm. (Austral-Magallanes Basin, Argentina) in which not enough data was available to cross check the technique, we now analyze Vaca Muerta Fm. (Neuquen Basin, Argentina) core rock samples that have a thoughtful geomechanical characterization. In this work we compare the properties obtained by nanoindentation to those obtained from a validated geomechanical model. Additionally, we compare nanoindentation data with laboratory tests obtained by static and dynamic experiments at plug scale. The results show that the elastic modulus obtained by nanoindentation matches the elastic modulus obtained with ultrasonic wave test under high confining pressure. Furthermore, it correlates to the ones obtained by triaxial compressive tests as well as with the modulus obtained from a calibrated geomechanical model. Additionally, good correlation is also seen when hardness data from nanoindentation is compared with uniaxial compressive strength (UCS) measured in plugs and with scratch resistance from core samples, but in a different order of magnitude. Using the elastic modulus and hardness obtained from nanoindentation we were able to screen data equivalent to confined dynamic Young modulus, UCS and scratch resistance measured in the cores. Therefore, nanoindentation in cutting is a cheap method to obtain mechanical properties when information or samples are not available, valuing cutting samples obtained prior to drilling new wells and getting cores and logs. Furthermore, it could be useful to determine the variations of these properties in horizontal wells where sonic logs are expensive and difficult to run.

INTRODUCTION
Exploration projects often rely on drill cuttings as the sole source of rock samples from a given area of interest. However, estimating the mechanical properties of these cuttings is a challenge due to the small sizes of the samples. Fortunately, the nanoindentation technique can overcome this issue, as demonstrated by several studies (Shukla et al., 2013; Glover et al., 2016; Ma et al., 2020). This method allows the determination of the indentation modulus, hardness, and fracture toughness of rock samples using a small amount of material from the measurement of load-displacement curves. Previous research has shown that there is a strong correlation between the indentation modulus and the dynamic Young modulus (Kumar et al., 2012; Dang et al., 2017; Celleri et al., 2020, Noya et al., 2021), indicating that the former can be used to describe the elastic behavior of rock samples during dynamic tests at high confining pressures.
Molecular Dynamics Insights into Bioconversion Induced Matrix Strain
Authors: Pandey R. , Sohail T. , Ajibona A. I. , Saurabh S. 
Published: September 2023

ABSTRACT
The total annual US consumption of natural gas is expected to surpass 40 trillion cubic feet in the coming years. Microbially enhanced coalbed methane (MECBM) aims to replicate naturally occurring microbial pathways to generate methane from in-situ coal. In a basic gamut of lab-characterization experiments investigating properties of coal as a reservoir, it was revealed microbial treatment of coal results in swelling of the coal matrix. Bio-strains in the matrix result in changes in connected porosity, and its stress-state which governs the flow behavior throughout the life of the producing reservoir. Use of molecular dynamics (MD) enables us to utilize the bio-strain data to understand the dynamic stress-state development in a MECBM reservoir. The Wiser coal molecule was used as the representative molecule, whose reactive potential was minimized using PCFF. The stable MD system enables application of strain, which enables the analysis of internal stresses. Results indicated internal stresses developed during bioconversion exceeded the Von Mises failure criterion for the sample tested in the laboratory under hydrostatic pressure (0.2 MPa). However, the internal stresses for sample under in-situ stress regimes was suppressed, far from the tensile failure conditions.

INTRODUCTION AND BACKGROUND
There has been a sustained increase in the demand for clean energy sources such as hydrogen and methane, especially as the world works towards meeting sustainable climate goals (Jun et al., 2016). Natural gases like methane have lower carbon footprint, as it generates approximately 50% of the carbon when compared to burning oil and coal for electricity generation (Tollefson, 2012). As such, natural gases are set to go up in production rates to meet environmental demands. Recent data indicates that the world demand for natural gas is expected to increase till 2045, with a significant portion of this demand to be met by increasing production from unconventional resources, such as coalbed methane (CBM) (Birol, 2017; Gonzales, 2021; IEA, 2022). CBM refers to naturally occurring methane extracted from coal and coal seams, which is an unconventional source of natural gas (Haldar, 2018). However, to meet the increasing demand for natural gas, researchers have made efforts to find ways to increase the production of coalbed methane. One such method is to replicate the natural production of methane formed by microbial breakdown of organic components present in coal (Flores et al., 2008; Strapoć et al., 2008; Midgley et al., 2010; Penner et al., 2010). This process of producing microbial methane from coal is referred to as Microbially Enhanced Coalbed Methane (MECBM) (Scott, 1999).