bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acoustic Response During Brine-CO2 Relative Permeability Testing of Bluff and Entrada Sandstones
Authors: Czarnota R. , Rinehart A. J. , Luhmann A. , Wang S. , Grigg R. 
Published: September 2022

ABSTRACT:
We present experimental results of brine and supercritical CO2 (scCO2) relative permeability experiments with active ultrasonic monitoring at reservoir conditions in the Bluff and Entrada Sandstones (NM, USA) from outcrop, which are being considered as possible geologic carbon storage targets, at reservoir conditions. The Bluff and Entrada Sandstones have distinct differences in grain size and cementation composition and amounts. We measured their relative permeability properties curves on outcrop rock using a steady-state method at possible reservoir conditions of elevated temperature and high pressure, i.e., at 85 to 89°C and, 22.8 to 24.1 MPa pore pressure in a CoreLabs Acoustic Core holder. To better understand scCO2 plume migration and residual trapping, both drainage and imbibition relative permeability were measured with increasing and decreasing fractional flows. At every steady saturation reached, we estimated the relative permeability measurement and measured the compressional wave velocity (Vp), and two shear wave velocities (Vs and Vs*) at the 500 kHz using a multichannel pulser-receiver. We found that Vp decreased and Vs and Vs* increased slightly as brine saturation decreased. This is consistent with the literature and further supports using seismic monitoring of the CO2 plume. Most tests revealed hysteresis in Vs and Vs* indicating possibly significant lithology dependent pore-scale processes leading to isolation of portions of the rock. This suggests that, at the laboratory scale, acoustic monitoring may reveal residual trapping mechanisms, transient wetting behavior, and other fluid-framework coupling to shear waves tied to different pore structures and surface chemistry related to the primary and diagenetic fabrics of the rocks.

1. INTRODUCTION
Geological storage of carbon dioxide (CO2) into deep saline aquifers has emerged as a potentially effective way to reduce our emissions of greenhouse gases. Monitoring of multiphase flow properties are needed to characterize the extent of CO2 mobility across the reservoir but are challenging to link to log- and reservoir-scale behavior. Acoustic-based studies measure elastic wave velocities including anisotropy and can be used in the calibration of sonic logs and to inform 3D/4D seismic and microseismic interpretations (Falcon-Suarez et al. 2020). The CO2/brine flow in a saline aquifer has two distinctive borders: 1) plume front where CO2 contacts brine (drainage); (2) after the initial front passes, CO2 is then displaced partially by brine (imbibition). In this study, we link relative permeability and brine/CO2 saturation measurements and variations in acoustic velocities during a cycle of drainage and imbibition.
Impact of Oil Based Mud on Chemo-Mechanical Properties of Cuttings and its Treatment
Authors: Martogi D. , Prakash R. , Varanasi V. R. S. B. , Abedi S. 
Published: September 2022

ABSTRACT:
In this study, we investigated the chemo-mechanical properties of cuttings contaminated with oil-based mud (OBM) and its various treatments. Rock fragments are obtained from Eagle Ford and Marcellus formations, which are then cut into cuttings with sizes ranging from 4 mm to 8 mm. The Eagle Ford sample is a carbonate-rich organic free sample, while the Marcellus sample contains a mixture of Calcite, quartz, and clay. We contaminated each sample with OBM under controlled pressure and temperature conditions. We then cleaned the samples using several treatment methods: wiped with cotton buds, soaking in a solvent, and soaking in diesel. Chemo-mechanical properties before and after contamination of each sample were then studied using micro-indentation technique and scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS). In doing so, the analysis was performed on samples’ cross-sections to study properties changes across the depth of contamination. A discussion on mechanical and chemical evolution across the sample depth will be presented. Degradation in mechanical and compositional properties are observed most severely on samples treated by solvent soaking. Wiping off OBM from the samples surface was found to preserve samples’ chemo-mechanical properties the most. Higher cuttings to OBM contamination ratio and higher cuttings to solvent ratio were observed to have more adverse effects on cuttings integrity.

1. INTRODUCTION
Completions quality is an essential factor in evaluating the economic viability of a reservoir. Completions quality relies on a good understanding of rock mechanical properties (i.e., elastic, strength, and fracture properties), the in-situ stress magnitudes, orientations, anisotropy, and rock mineralogy to determine the most effective completions design and treatment (Prioul et al. 2016, 2018). Typically, these properties are measured through laboratory testing on cores, outcrops, and well logging. Though cores are preferred, they are only acquired on a select number of wells due to cost and are typically taken on the vertical section of the wells. Well loggings are usually performed on select wells during the exploration phase and are limited to acquisition resolution. Drill cuttings, however, are continuously collected and transported to the surface throughout drilling and are available throughout the vertical and lateral sections of the well at no additional cost. Cuttings have been shown to be a valuable resource for determining petrophysical properties (i.e., permeability, organic content, porosity, density, mechanical properties) in cases where cores collection and logging are not economically viable and technically challenging (Ortega et al., 2012; Olusola et al., 2014; Prioul et al., 2016; Althaus et al., 2020; Sanei et al., 2020).
Optimal Design Method of Oscillator Installation Position in Sliding Drilling
Authors: Shi Xiaolei , Huang Wenjun , Gao Deli , Yang Guang , Wang Wenzhi 
Published: September 2022

ABSTRACT:
In the process of sliding drilling, installing oscillators on drill strings can decrease axial friction and increase wellbore extension effectively in sliding drilling. Traditionally, the positions of oscillators are most determined by drilling experience, which constraints the drag reduction efficiency of oscillators. To overcome this shortcoming, a new optimization design method of oscillator installation position is presented. Firstly, the initial position of the drill bit is determined according to the well structure data, drilling parameters and drilling time. Then, the drill string in the borehole is divided into key nodes according to the joint position. Based on the data of screw induced torque, the action length of screw induced torque is calculated, and the action length of static friction zone is determined. Next, based on the initial conditions and boundary conditions, establishes a dynamic model of drill string by considering the friction nonlinearity and uses finite difference method to solve it, the friction distribution of drill pipe is analyzed, and the friction of key nodes in each distribution area is calculated. Finally, the initial position of the drill bit and the action length of the static friction zone are re-determined, and the friction of key nodes is accumulated. By analogy, the maximum accumulated friction in the static friction area is determined. Based on the oscillator’s propagation distance model and the minimum drag reduction efficiency, the recommended best installation position is calculated, and sensitivity analysis is carried out to evaluate the drag reduction effects of various parameters. The results show that, compared with the calculation results of determining the installation position of oscillator by drilling experience in the past, the model in this paper has a more significant effect on reducing friction and the installation position is more reasonable. The fluctuation of the displacement of drill string and the hook load are more obvious when the oscillators are installed in the preferred position, and the effect of reducing the average friction is significant, which is more conducive to the transfer of axial force. When other parameters are constant, using the recommended positions of oscillators or increasing the number of oscillators can not only beneficial to the transmission of axial force, and can reduce the average friction of the drill string, but also improve the drag reduction efficiency of the drill string, increasing the rate of penetration and increasing the borehole extension distance. The research results are of significant guiding significance for optimal design and safety control of drag reduction oscillators in sliding drilling.
Micromechanical Modeling of Shale-Indentation Experiments Imaged by Synchrotron X-Ray Micro-Tomography
Authors: Rutqvist J. , Voltolini M. , Kneafsey T. J. 
Published: September 2022

ABSTRACT:
We present micromechanical modeling of an indentation experiment on Green River Shale with simultaneous X-ray micro-computed tomography of internal sample deformation that provides new insights into the ductile-brittle micromechanical behavior of shales relevant to proppant embedment. Brittle wing cracks appear from the indenter along the shale bedding, but indentation depth is dominated by ductile plastic shear deformations governed by extreme compressive stress magnitudes below the indenter-shale contact. Simultaneous analysis of the experimental loading-unloading indentation curves and the imaged shale deformations were used to constrain elasto-plastic properties and strength anisotropy of the tested Green River shale sample.

1. INTRODUCTION
The evolution of rock fractures and their fluid transmissivity are critical in underground energy geosciences activities, such as hydrocarbon production, carbon sequestration, geothermal energy, and nuclear waste disposal (Rutqvist and Stephansson, 2003). The fluid transmissivity of a fracture depends on factors such as the local stress across the fracture, fracture surface roughness, shear displacement offset, and host rock properties (Barton et al., 1985). In hydrocarbon production, proppants such as sand are frequently injected into fractures to keep them open for enhanced hydrocarbon production (Kadende et al., 2021a). However, even proppant-filled fractures may close significantly because of embedment of the proppant into the fracture surfaces and proppants may also be crushed under high stress (Kantende et al., 2021b). The embedment of proppants may be particularly severe in shales high in organic carbon or clay, shales that may be characterized as self-sealing (Bourg, 2015).
In this study we present micromechanical modeling of an indentation experiment on a soft Green River shale of high organic carbon content. The experiment was conducted under simultaneous synchrotron X-ray micro-computed tomography to image internal three-dimensional sample deformation. This include tomographic images of internal deformation anisotropy, fracturing, and surface pileup adjacent to the indenter. The modeling presented in this paper shows that matching the experimental loading-unloading indentation curves and the shale deformation field in three dimensions can be used to constrain elasto-plastic properties and strength anisotropy of the tested shale sample. The work also provides new insights into the ductile-brittle micro-mechanical behavior of shales relevant to proppant embedment.
Cooling-Induced Acoustic Emissions in Westerly Granite: Implications for in Situ Stress Measurement
Authors: Trzeciak M. , Sone H. , Wang H. , Nakagawa S. , Voegeli S. 
Published: September 2022

ABSTRACT:
Thermally induced stress changes in rock lead to creation and reactivation of microcracks with accompanying acoustic emissions (AEs). Therefore, monitoring AEs during cooling (or heating) of rock potentially allows us to determine the rock’s original stress state. This approach would require predicting time-dependent changes in the thermally induced stress and applying an appropriate AE-based failure criterion, so that the in situ stress can be determined by subtracting the induced stress from the failure stress. The goal of this research is to develop a technology to determine the stress state in geothermal reservoirs by cooling the borehole circumference and detecting the onset of microscale rock failure. As the first step to achieve this goal, we examined spatio-temporal evolution of AEs which were thermally induced in Westerly Granite blocks by abrupt local cooling. Four sets of experiments were conducted with different sample and cooling geometry, stress state, and preexisting damage (cracks). The preliminary results indicate that the onset of AE activity can be correlated best to the thermal front propagation in rock samples and to the applied stress. Interestingly, pre-existing microcrack damage in rock had little impact on the AE onset behavior. The conditions that lead to the onset of AE activity and its relation to the ultimate tensile strength of rocks – a parameter which is determined from conventional rock testing – are still poorly understood, which requires further investigation.

1 INTRODUCTION
Sustainable development of geothermal energy resources requires detailed knowledge about the in situ stress state in the target rocks. In deep boreholes, stress estimation commonly relies on analysis of wellbore wall failures, break-outs and drilling induced tensile fractures, which develop spontaneously after the well is drilled (e.g. Zoback et al., 2003). Active methods of stress measurement are usually limited to hydraulic methods for estimation of the least principal stress (De Bree and Walters, 1989). Several methods of active stress measurement, capable of constraining the entire stress tensor have been proposed, e.g. overcoring (Worotnicki, 1993), hydraulic tests on preexisting fractures (HTPF) (Cornet, 1983), or sleeve fracturing (Stephansson, 1983). However, each of these methods has their associated technical difficulties or deficiencies which make them unpopular in practical application in deep environments.
An Integrated Geology-to-Geomechanics Workflow to Assess Geomechanical Risk of CO2 Geological Storage
Authors: Sun Zhuang , Cosson Camille , Plougoulen Aurore , Datye Deepak , Fager Andrew , Crouse Bernd 
Published: September 2022

ABSTRACT:
Full-scale implementation of CO2 storage requires a number of challenges to be addressed, among them is reliably assessing geomechanical risk at storage sites. A 3D mechanical earth model (MEM) can be used to understand how rock types and stresses are distributed in the 3D space of the reservoir and surrounding formations. However, due to meshing limitations, the MEM is typically derived from simplified geological frameworks and does not relate with static and flow simulation models anymore. To overcome these difficulties, we have developed a general solution to readily assess the geomechanical risk of CO2 geological storage while preserving the geology’s integrity. We present a case study based on an offshore field in which the storage formation is composed of stacked anticlinal sandy layers sealed by shaly caprocks. We investigate fault stability by explicitly simulating the fault slippage and observe a significant fault reactivation with a maximum magnitude of ~ 0.3 m. A high resolution sub-model of the near-wellbore region indicates a stable wellbore condition. This workflow permits us to combine a reliable representation of the subsurface with a state-of-the-art rock mechanics finite element solver, which can be leveraged across the entire lifecycle of CO2 storage.

1. INTRODUCTION
CO2 geological storage is a proposed solution to curb carbon emissions to the atmosphere (Bachu, 2008; Benson and Cole, 2008; Bickle, 2009). A large-scale CO2 storage project requires annual CO2 injection of millions of tons into deep geological media where the caprock and faults provide structural trapping of CO2 (Michael et al., 2010; Fuss et al., 2014; Tang et al., 2021; Wu et al., 2021). However, full-scale implementation of CO2 storage requires a number of challenges to be addressed, among them is reliably assessing geomechanical risk at storage sites (Rutqvist, 2012). For instance, CO2 injection increases the pore pressure and reduces the effective stresses, which may reactivate existing faults or induce damaging geomechanical changes to the caprock (Cappa and Rutqvist, 2011; Faulkner et al., 2018; Ju et al., 2021; Sun et al., 2021b). Fault reactivation is one risk of CO2 storage because it may compromise the sealing behavior as well as induce seismic events (Zheng et al., 2009; Apps et al., 2010; Zoback and Gorelick, 2012). Therefore, it is critical to maintain the integrity of caprock and faults to ensure the long-term CO2 storage security.
The Comprehensive Effects of Group Fracturing and Depletion Redistribution in Low Permeable Reservoirs
Authors: Qu H. Y. , Lang H. , Xue X. J. , Da Y. P. , Zhou F. J. , Liu X. Y. 
Published: September 2022

ABSTRACT:
Refracturing is an effective way to drain the unstimulated rock through diversion treatment. The refrac geometry is determined by the reorientation and change in the magnitude of the in-situ stress. However, the comprehensive impact of primary fracturing, water injection and oil production in well group on the stress redistribution has not been well understood. A three-dimensional heterogeneous geomechanical model coupled with unconventional fracturing and reservoir simulation was established. Following the primary hydraulic fracturing and water injecting according to the pumping and injection schedule of an inverted nine-spot well group, an automatic gridding algorithm was run. In addition, history match and 10-year production prediction were conducted through reservoir simulation. A 3D geomechanical finite element solver was utilized to compute the spatial and temporal change in the in-situ stress and deformation during fracture propagation and reservoir depletion, providing updated stress profiles. Refrac simulation scenarios were run after production of 1 year, 3 years, 5 years and 9 years to identify the most opportune time to refrac the well group. Results indicate that the impact of water injection on stress is consistent with hydraulic fracturing while opposite to that of the reservoir depletion. The magnitude of horizontal principal stresses increases around the injection well, while the stress contrast decreases during the water injection. Hydraulic fracturing induces tensional and compressional stress perturbation around the producing well in the vicinity of fracture tips and fracture walls while the stress is released as the well produces. In addition, the magnitude of stress variation in the well group increases with the depletion at the beginning, followed by a decrease. It is beneficial to refrac the well group 3 years after the first treatment. The impact of water injection, primary hydraulic fracturing and well depletion on the variation of in-situ stress was clarified through an integrated modeling in this study, providing insights for the design and evaluation of refracturing treatments to enhance the field development of the low permeable reservoirs.
Effect of Cement Behaviour on Casing Integrity in Superhot Geothermal Wells: A Numerical Study
Authors: Hoang N. H. , Bois A. P. , Naumann M. , Sæther S. , Coudert T. 
Published: September 2022

ABSTRACT:
This paper presents the results of numerical studies aiming to assess the effects of cement hydration on the casing integrity in superhot well conditions. Casing integrity challenges for high and super-high temperature geothermal wells were first discussed. A simplified well cement material model was implemented in the stand-alone code, Casinteg, to simulate cement behaviour in field conditions. Numerical simulations were performed, based on the IDDP-2 well scenarios, to investigate the effect of cement retarders, cement hydration heat and cement shrinkage on the casing stresses. The obtained results have shown that by engineering proper cement solutions, the risks of casing failure in geothermal wells can be minimized to sustainably harvesting green power from superhot geothermal reservoirs.

1. INTRODUCTION
To answer the growing need for energy and at the same time fighting against the global climate change, development of renewable energy sources is indispensable. Geothermal energy is today recognized as one of the potential renewable sources, contributing to the "green shift" from fossil fuels toward more sustainable energy. Currently, most commercial geothermal power plants operate at the temperature range of 150° – 300° C. However, exploring the huge potential from/of? super-high temperature reservoirs (up to 400° – 500 °C) may be needed to increase the power production output, thereby lowering levelized cost of electricity (LCOE) of geothermal projects (Reinsch et al., 2017).
For sustainable exploitation of geothermal energy, robust and cost-efficient casing systems are an absolute demand. However, the harsh operation conditions encountered in the high-temperature (HT) geothermal reservoirs are very challenging and are detrimental for the well integrity. Improper material selection and design principles may lead to serious failure events, and loss of the production well, as reported in many HT geothermal well projects (Ford et al., 2017). Recent examples are experiences from the Iceland Deep Drilling Project (IDDP). The two first IDDP wells are themselves pilot experiments and great learning sources for both researchers and industry. However, they could not be used for power production due to well integrity problems. Both wells experienced severe casing damage/failure (casing collapse and corrosion), which were the main technical obstacle to tap geothermal power from these ultra-high temperature production wells (Kruszewski and Wittig, 2018).