bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Oriented Perforation Strategy for Fracturing Deep and Tight Gas Reservoirs
Authors: Xia K. , Mahmood T. , Cui Y. 
Published: November 2022

Abstract
Hydraulic fracture initiation can be a challenging issue for fracturing deep and tight gas reservoirs, which generally requires a high breakdown pressure for clustered perforation hydraulic fracturing treatment. Oriented perforation represents a potential solution to alleviate this issue, which can not only lower breakdown pressure but also deliver a better oriented fracture geometry. In this paper, we present a new strategy to tackle this issue, which includes a framework to calculate the breakdown pressure, optimum perforation direction, and a new perforation cluster layout design. The optimum perforation direction is defined as the one, along which hydraulic fractures can be initiated with the lowest breakdown pressure for a perforation cluster. It can be used to control the perforation device rotating and fired at the right direction in subsurface. Further we present a new perforation cluster layout design, which can alleviate the near wellbore fracture tortuosity and deliver a better fracture initiation when it is aligned along the optimum perforation direction in the subsurface. The two parts of the strategy working together, fracture initiation from a perforation cluster can be achieved a lot of easy than using the conventional perforation method. This new perforation strategy can further alleviate the near wellbore fracture tortuosity, minimize fluid flow restriction and reduce pressure friction loss during hydraulic fracturing treatment. Otherwise multiple and reoriented nonplanar fractures originated from the wellbore perforation cluster likely lead to a premature screen-out, which can negatively impact fluid injection to achieve a desired stimulation performance. Hydraulic fracturing treatment in deep and tight gas reservoirs can be improved through the following actions: calculating breakdown pressure and optimum perforation direction, using new perforation cluster layout design, and aligning the perforation cluster in the optimal direction in subsurface.
Third-Order Padé Thermoelastic Constants of Solid Rocks
Authors: Yang J. , Fu L. Y. 
Published: November 2022

Abstract
Classical third-order thermoelastic constants are generally formulated by the theory of small-amplitude acoustic waves in cubic crystals during heat treatments. Investigating higher-order thermoelastic constants for higher temperature is a challenging task because of more undetermined constants involved. However, even at low temperatures, these Taylor-type thermoelastic constants encounter divergence in characterizing the temperature-dependent velocity changes of elastic waves in solid rocks as a complete polycrystal compound of different mineral lithologies. Therefore, we propose third-order Padé-type thermoelastic constants derived by the approximation of Padé rational function to the total strain energy. The Padé thermoelastic constants are characteristics of a reasonable theoretical prediction for acoustic velocities of solid rocks even at high temperature. The results demonstrate that the third-order Padé thermoelasticity can characterize thermally induced velocity changes more accurately than the conventional third-order Taylor thermoelasticity, and have the same accuracy for the corresponding higher-order thermoelastic model. The Padé approximation could be considered a more versatile model for describing thermal velocity changes for polycrystals and solid rocks. The physics of the Padé coefficients is relevant to the thermal expansion mismatch and thermally induced deformation of microcracks.

Introduction
Temperature significantly changes the mechanical and physical properties of rocks, which becomes importance in many fields of earth sciences and geological engineering. Temperature-induced variations in elastic properties generally present strong nonlinearity even at low temperature because of the differential thermal expansion of multimineral rocks. The classical theory of thermoelasticity is formulated on account of the Taylor power series of the Helmholtz free energy functions (Dillon, 1962). The resulting second- and third-order thermoelastic constants have been widely used for crystals, but with certain insufficiencies in representing the temperature-dependent velocity changes of elastic waves for rocks like a completely polycrystal compound of varying mineral lithologies. The investigation of higher-order thermoelastic constants could be useful for understanding the nature of nonlinear behavior in heating rocks, but involves more undetermined constants and becomes a challenging task. As a more effective alternative, this article addresses a nonlinear thermoelasticity for solid rocks relied on the Padé approximation of Helmholtz free energy functions.
Geomechanical Modelling of Borehole Breakouts and Compaction Bands in High-porosity Sandstones
Authors: Bere A. B. 
Published: November 2022

Abstract
Predicting the nature and extent of deformation adjacent to wellbores can be critical for successful subsurface operations. The ability to capture the onset and evolution of failure can permit more efficient operations and circumvent or minimize the effects of well-known operational issues such as wellbore instability and sand production. In this paper, the behaviour of porous sandstones is investigated through replication of experimental testing conducted by Haimson (2004). In this work the deformation near the excavated section for highly porous sandstones was documented and analyzed, with contrasting deformational styles observed that are tentatively attributed to mineral composition. The requirements for predicting these styles are discussed and presented within a novel three-field modelling framework that incorporates a sophisticated constitutive model. Application of the workflow and results for breakout and sand control studies is discussed, along with potential future extensions to the capabilities of the constitutive model.

Introduction
Instability of subsurface excavations is critical and can pose serious problems affecting the timing and success of a project. Prediction of such instabilities has long been recognised as a key factor in many industries. Understanding the failure mechanisms is vital for the optimisation of well production as instabilities affect drilling efficiency, resulting in lost circulation, breakouts, or hole closure and even in loss of the open-hole section due to stuck and damaged drill pipe (Lang et al., 2011). Nevertheless, such instabilities are useful for informing on stress directions and magnitudes (Haimson and Song, 1993). Borehole logging has been long used to estimate stress directions, based on the location of the breakouts around the well (Brudy et al., 1997; Zoback et al, 2003; Kingdon et al., 2016). In addition, several studies have suggested that the characteristics and dimensions of the breakouts, if properly measured, can also inform on the magnitudes of far-field stresses.
PFC Modelling on Natural Weak Planes of Laminated Shale and Their Influences on Tensile Fracture Propagation
Authors: Anyimah Peter Owusu , Meng Leifeng , Cheng Shizhong , Chakma Nabayan , Sheng Mao , Shahid Arshad Shehzad Ahmad 
Published: November 2022

Abstract
Laminated shale reserves various natural weak planes involving some bedding planes, natural fractures and mineral dykes. The obvious phenomenon of the interactions between hydraulic fractures and bedding weak planes were observed involving arrest, crossing, and diversion in previous works. Moreover, the bedding angles, cement mineral compositions of natural weak planes, and net pressure of hydraulic fracture were considered as the primary factors to determine the type of interaction. However, the rock failure modes and characterization of weak planes from micromechanics has been yet addressed. In this paper, a Particle Flow Code (PFC) model on natural weak planes of laminated shale was proposed by considering micromechanical properties including the cohesive strength, stiffness, elastic modulus, and friction angle. The PFC model was validated by the three-point bending tests on a typical laminated shale. The influence of weak plane angles, elastic modulus, and strength of weak planes on tensile fracture propagation were obtained. Their interaction types and dominant failure mode from tensile to shear were analyzed. It concludes that fractures divert in the inclined angles and low strength of natural weak planes, crossing occurs in the opposite case.

Introduction
Shale oil and gas formation normally reserves various natural weak planes involving the weak bedding planes, natural fractures and mineral dykes. It is evident that the natural weak planes affect hydraulic fracture geometry. The obvious phenomenon of the interactions between hydraulic fractures and bedding weak planes were observed involving arrest, crossing, and diversion in previous works. Moreover, the bedding angles, cement mineral compositions of natural weak planes, and net pressure of hydraulic fracture were considered as the primary factors to determine the type of interaction. However, the rock failure modes and characterization of weak planes from micromechanics has been yet addressed.
Geomechanical Approach of Induced Seismicity using Cohesive Zone Elements
Authors: Pouya Amade , Deptulski Rafael , Ahn Kyeung Hye , Rebel Estelle , Boisson Michel 
Published: November 2022

Abstract
This study aims to demonstrate the capability to account for seismic and aseismic responses due to fault reactivation using a cohesive zone model in a Finite Element framework. We adopt an elastic-damage-plastic formulation to predict the fault reactivation while considering unilateral effects observed in geomaterials. In a conceptual 2D problem representing two layers of rock separated by an existing fault, we apply displacement-driven and stress-driven shear loading to provide a first characterization of the instabilities and energy dissipation. Qualitative and quantitative analyses of the dissipative process are provided through the shear stress field and the evolution of the shear stress, displacement, and energy balance. We obtain through the present model the total of dissipated energy thanks to the energy balance. Also, while the elastic energy variation can be positive or negative depending on the type of boundary conditions (stress-driven or displacement-driven), the radiated elastic energy is always positive during seismic events. It is so a good candidate to determine the seismic moment.

Introduction
Instabilities in faulted mechanical systems are at the heart of numerous recent studies related to micro-seismic phenomena induced by human activities. Increasing interest to assess the potential for activation of existing faults in geologic sites has been observed in different applications such as CO2 sequestration (Nguyen et al., 2019), waste-water disposal (Walsh and Zoback, 2015), recovery of hydrocarbons (Davies et al., 2013), geothermal facilities (Majer et al., 2007) and nuclear waste disposal (Urpi et al., 2019). Several previous studies showed that both natural and anthropogenic factors determine fault reactivation phenomena (McGarr, 2014; Segall and Lu, 2015; Fan et al., 2016). The lack of long-term historical monitoring of seismic activity in candidate sites to host in-deep geological applications is an important drawback to assess the risks through empirical models. For this reason, numerical models were mainly used to predict fault reactivation response (e.g. finite element method (Haddad and Eichhubl, 2020), discrete element method (Langhi et al., 2010), finite difference method (Lee et al., 2013)).
Discrete Element Study on Rock Failure Mechanism by Shaped PDC Cutter Under Formation Conditions with In-Situ Stress and Temperature
Authors: Yao Jianlin , Liu Bin , Zhu Haiyan 
Published: November 2022

Abstract
Polycrystalline diamond compact (PDC) bits have been widely used in drilling process due to their high efficiency and great reliability. To investigate rock failure mechanism and further improve the performance of PDC bits, a series of single cutter tests have been conducted in previous studies. However, most of them were performed under atmosphere conditions. That is, the effects of temperature and in-situ stress were ignored due to the limitation of experimental facility, which restricts the developing of novel bits. To solve the aforementioned problem and deeply study the rock failure mechanism of PDC bits, numerical simulation researches were conducted based on the discrete element method (DEM). Firstly, a numerical triaxial test model was established to calibrate microscopic parameters of rocks that collected from Sichuan basin Ziliujing formation. Then, boundary conditions such as bottom hole temperature, surrounding pressure and hydrostatic pressure were loaded to rocks, thus simulating the actual bottom conditions. Based on this model, rock failure characteristics under the impacts of cutters with different shapes (cylindrical cutter, triangular prismatic cutter, ridge cutter, V-cutter) and different cutting parameters (cutting depth, back rake angles, etc) were studied. The results indicate that the triangular prismatic cutter has the greatest rock-breaking efficiency in our studies, followed by V-cutter and cylinder cutter. The triangular prismatic cutter can obtain the highest rock cutting efficiency when the cutting depth, back rake angles and the diameter of cutter are equal to 2 mm, 20 degrees and 16 mm respectively. The present study provides an in-depth understanding on rock failure mechanism and a basis for the development of efficient PDC bits.

Introduction
The Sichuan Basin is rich in natural gas resources and is one of the major gas production regions in China. However, the corresponding geological conditions are complex. Under the impacts of high temperature and high pressure at the bottom hole, the formation rock becomes highly abrasive and poorly drillable, resulting in a significant decrease in the drilling speed. To improve the drilling efficiency and enhance the performance of PDC bits, it is necessary to carry out studies on cutting and investigate rock failure mechanisms under the actual bottom hole temperature and pressure.
Selection of Sand Control Completion Techniques Using Machine Learning
Authors: Laoufi H. , Megherbi Z. , Zeraibi N. , Merzoug A. , Ladmia A. 
Published: November 2022

Abstract
Sand production is one of the major problems in many oil and gas assets around the world. Uncontrollable sand production can affect hydrocarbon recovery and increase operational costs. This paper aims to develop a classification approach to suggest the optimal sand control method using machine learning algorithms. Four different models have been used, namely K-Nearest Neighbors, Support Vector Machine, Random Forest and Decision Tree. After extensive exploratory data analysis, nine parameters were included in the model: Sorting coefficient D10/D95, Mass fraction smaller than 44 micron, Well deviation angle through the pay zone, Pay-zone true vertical thickness, Bottom hole pressure, Maximum oil rate, Maximum gas rate, Permeability, Well type. By comparing the different models in this study Random Forest classifier achieved the highest evaluation metrics: f1-score of 0.9568, precision of 0.9580, and recall of 0.9568 respectively. These results combined with the confusion matrix to assess the model performance have shown that up to a certain level machine learning methods can ensure the adequate completion for the candidate well. The proposed work turns out to be a potential approach that rises to the level of a decision support tool and thus can help engineers set the right completion option.

Introduction
Sand production has always been one of the major concerns for the oil and gas industry. It is the result of the migration of failed sand grains because of the drag forces caused by fluids flow from an unconsolidated reservoir. Generally, this phenomenon leads to technical problems such as erosion of downhole equipment and surface facilities, production loss, well access obstruction, and economic effects represented by the additional cost of sand disposal. Sand control is, therefore, necessary to mitigate the effect of sand production on hydrocarbon wells. Judhan (2016) defined sand control as all the techniques that allow hydrocarbons production without sand grains production in the wellbore. Sand control consist of two methods: passive and active. Passive sand control methods are generally used to reduce sand during the first stage of production when the sanding rate is low, as this latter gradually increase, active sand control will be required.
Reducing Uncertainty in the Pore Pressure Profile of the Most Important Unconventional Argentinian Play: Vaca Muerta
Authors: Rodríguez L. G. , Moreno Cardenas J. P. , Mónaco A. , María S. , Osorio Gallego J. G. , Alvarez J. B. Angel 
Published: November 2022

Abstract
In the centre of the Neuquén Basin, the Vaca Muerta formation is a 400 m thick over-pressurized shale characterized by presenting a 100% marl lithology with Total Organic Carbon (TOC) contents that can exceed 10 wt.%. This condition causes important logs distortion since it reduces their dependence on the rock matrix, being even almost impossible to determine facial changes by conventional mudloging visual techniques.
This work is focused in La Calera block, an unconventional asset operated by Pluspetrol S.A (in partnership with YPF S.A.) where a theoretical and operational crosschecked methodology was established as to reduce the Vaca Muerta pore pressure uncertainty.
Data from LCa.x-3001, the first unconventional exploration well in the block, was used to calibrate a Bowers’ pore pressure model, including lithology descriptions, operational and drilling events, and MPD tests. In addition, kerogen corrected synthetic sonic logs were incorporated in the pore pressure estimation workflow as a more accurate input, avoiding logs distortion.
The pore pressure model built for the Vaca Muerta formation show highly precise results, being implemented to date on 40 unconventional wells, with optimal performance, neither well loss nor Geological/Geomechanical NPTs.
Finally, X-Ray Fluorescence (XRF) from a Vaca Muerta horizontal well was used as a crosschecking input since it acts as an accurate indicator of facial changes and paleoenvironmental variations, existing high correlation between some elemental concentrations and the pore pressure variations.

Introduction
On the west part of Argentina, the Neuquén basin has been producing oil and gas from several proved conventional plays for more than 100 years (Carbone et al., 2020). In the last decade, Vaca Muerta has become a world-class example of an unconventional reservoir, being by its own the Argentina's most important energy source, with estimated resources around 20 to 40 Bbbl (Billion barrels) of oil (Gutiérrez Schmidt et al., 2014) and 150 to 250 TCF (Trillion Cubic Feet) of gas. Considering the country current consumption, it can supply its energy demands for the next 100 years.
3D Geomechanical Reservoir Modelling in Faulted Reservoirs
Authors: Markou N. , Papanastasiou P. 
Published: November 2022

Abstract
In this study, we present a three-dimensional (3D) geomechanical reservoir model for a faulted and compartmentalized reservoir in the Eastern Mediterranean. A series of alternative production scenarios performed using a simulation model that accounts for consolidation and plasticity deformation of the rocks. Plastic yielding is mainly developed in fault slip zones of narrow extent whereas it appears that there is low risk of plastic behavior in the main reservoir. The slip conditions become complex in the fault contact surfaces where local areas close to fault connections are more pronounced to slip creating localized areas of smaller faulted zones. Displacement magnitudes, are controlled by the structural boundary conditions and the geometrical shape of each fault block. Overall, the higher displacements develop in the near fault region while in the remote from the fault area the vertical displacement is nearly constant as it is clearly governed by the reservoir depletion. Furthermore, changes of normalized permeability can be drawn in the 3D space providing additional insights of heterogeneous distribution.

Introduction
Petroleum geomechanics become important in reservoirs highly impacted by faults mechanics and overpressure zones. An operator has to well define the fault structural geometry of the field and assess early in the producing life of a reservoir whether production will be affected by the presence of naturally occurring fractures though some faults and fractures cannot be identified even at the early stages of a field production. Reservoir depletion increases the stress carried by the load-bearing grain frame of the reservoir rock. Stress analysis can be extended to identify rock failure conditions that can lead to the creation of new faulted systems in the subsurface formations. Geomechanics play an important role in identifying the stress conditions in a faulted reservoir system and the potential of slip activation of an existing fault. Extensive accounts on the importance of reservoir geomechanics can be found in the classical books of Fjaer et al., (2008) and Zoback, (2010). Finite element analysis can be used to simulate the tectonic movement to match borehole observations (Plumb et al., 1998).
A Multi-Physics Fields Coupling Model for Supercritical CO2 Seepage in Shale Formation
Authors: Bai Bing , Yao Bowen , Chen Mian , Jin Yan , Liu Di , Zhang Yu , Sun Mingwei 
Published: November 2022

Abstract
Supercritical carbon dioxide (ScCO2) can protect shale formation from hydration damage. When ScCO2 is utilized to develop shale oil and gas resources, it is necessary to establish the multi-physics fields coupling model to describe ScCO2 seepage in shale formation. The multi-physics model describing water-based fluid seepage is not capable explaining ScCO2 flow because of a great variation in physical properties of ScCO2 with pressure and temperature. In this study, a thermal–hydro–mechanical coupling model is constructed to describe ScCO2 seepage based on the transport and thermodynamic properties of CO2, combined with the effect of ScCO2 on mechanical properties of shale. The finite element method is used to solve the distribution of formation temperature, pore pressure and stress with time and position. The results show that compared with water seepage, the variation of formation temperature is greater, the pore pressure is lower, the stress difference near the wellbore in the direction of minimum in-situ stress is bigger, and the tangential stress in the direction of maximum in-situ stress is lower when adsorption-induced strain is neglected. The radial stress and tangential stress decrease with increasing time. This research can provide theoretical basis for wellbore stability analysis and fracturing evaluation when using ScCO2 as the drilling fluid and fracturing fluid, separately.

Introduction
As one of the unconventional resources, shale oil and gas resource is an important alternative to widely used conventional resources, which is attracting worldwide attention (Jin and Chen, 2019). Currently, the commercial exploitation technologies are massive hydraulic fracturing and horizontal drilling for developing shale gas resource. However, shale formation contains clay mineral, the hydration damage will be produced when clay mineral meets water. In the process of drilling or fracturing with water–based fluid, wellbore collapse or poor fracturing stimulation may be encountered due to hydration swelling. Meanwhile, hydraulic fracturing operation will consume a large amount of water resource, which limits the application of hydraulic fracturing in water–lacking area. In order to avoid formation damage and conserve water resource, the technology of drilling or fracturing with supercritical CO2 is proposed (Wang et al., 2018; Wen et al., 2020).