انجمن ژئومکانیک نفت ایراننشریه ژئومکانیک و ژئوانرژی2538-46518420260220Enhancing Oil Field Characterization Through Seismic Crosswell Tomography: A Comparative Study of Structured vs. Unstructured Meshing for Improved Inversion AccuracyEnhancing Oil Field Characterization Through Seismic Crosswell Tomography: A Comparative Study of Structured vs. Unstructured Meshing for Improved Inversion Accuracy11424795910.22107/ggj.2025.539990.1256FAامیریزدان پناهSchool of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran0009-0002-1749-1582میثمعابدیSchool of Mining Engineering, College of Engineering, University of Tehran, Tehran, IranJournal Article20250828Seismic crosswell tomography is recognized as a robust method for characterizing subsurface structures in oil field exploration. In this study, the effectiveness of structured and unstructured meshing strategies is evaluated for inverting seismic crosswell tomography data to enhance subsurface velocity imaging. A synthetic layered model, representative of oil field geology and incorporating gas, oil, and saline water anomalies with distinct velocity contrasts, is utilized to simulate wave propagation and reconstruct velocity distributions through a finite element-based approach. Structured meshing is found to provide computational stability and uniform resolution, suitable for simpler geological settings, though artifacts may be introduced in complex anomaly regions. In contrast, unstructured meshing is adapted to geological heterogeneity, thereby improving the resolution of anomaly-related velocity contrasts, albeit with increased computational requirements. Comparative analysis of velocity reconstructions, misfit distributions, and ray path coverage is conducted to elucidate the trade-offs between these meshing strategies, informing optimal mesh design for accurate subsurface characterization. The findings derived from this research significantly enhance the field of seismic crosswell tomography, particularly in the context of oil field investigations. This study is limited to synthetic 2D modeling, and the absence of field validation and 3D modeling warrants further investigation to confirm real-world applicability. By providing valuable insights into the intricacies of mesh optimization, this study paves the way for achieving exceptionally high-resolution geophysical imaging of subsurface hydrocarbon anomalies.Seismic crosswell tomography is recognized as a robust method for characterizing subsurface structures in oil field exploration. In this study, the effectiveness of structured and unstructured meshing strategies is evaluated for inverting seismic crosswell tomography data to enhance subsurface velocity imaging. A synthetic layered model, representative of oil field geology and incorporating gas, oil, and saline water anomalies with distinct velocity contrasts, is utilized to simulate wave propagation and reconstruct velocity distributions through a finite element-based approach. Structured meshing is found to provide computational stability and uniform resolution, suitable for simpler geological settings, though artifacts may be introduced in complex anomaly regions. In contrast, unstructured meshing is adapted to geological heterogeneity, thereby improving the resolution of anomaly-related velocity contrasts, albeit with increased computational requirements. Comparative analysis of velocity reconstructions, misfit distributions, and ray path coverage is conducted to elucidate the trade-offs between these meshing strategies, informing optimal mesh design for accurate subsurface characterization. The findings derived from this research significantly enhance the field of seismic crosswell tomography, particularly in the context of oil field investigations. This study is limited to synthetic 2D modeling, and the absence of field validation and 3D modeling warrants further investigation to confirm real-world applicability. By providing valuable insights into the intricacies of mesh optimization, this study paves the way for achieving exceptionally high-resolution geophysical imaging of subsurface hydrocarbon anomalies.http://www.irpga-journal.ir/article_247959_6a3c71009505145da46cd981040e5c45.pdfانجمن ژئومکانیک نفت ایراننشریه ژئومکانیک و ژئوانرژی2538-46518420260220Application of Extended Finite Element Method for Simulating Crack Initiation and Propagation Mechanism in Hydraulic Fracturing Processکاربرد روش المان محدود توسعه یافته برای شبیه سازی مکانیزم شروع و انتشار ترک در فرایند شکست هیدرولیکی153524796910.22107/ggj.2025.509057.1250FAمحمدرضازیرکدانشجوی دکتری در دانشکده مهندسی معدن و متالورژی دانشکاه یزد.0009-0001-4800-7370محمدفاتحی مرجیاستاد مکانیک سنگ در دانشکده مهندسی معدن و متالورژی دانشگاه یزد.منوچهرصانعیاستادیار دانشکده مهندسی معدن و متالورژی دانشگاه یرد0000-0003-0869-1988مهدینجفیدانشکده مهندسی معدن و متالورژی دانشگاه یزدَابوالفضلعبداللهی پوردانشکده مهندسی معدن، دانشکده فنی، دانشگاه فنی دانشگاه تهران0000-0003-2687-4470Journal Article20250828The Extended Finite Element Method (XFEM) is a powerful numerical method for simulating crack initiation and propagation, particularly in unconventional hydrocarbon reservoirs such as shale and tight gas formations. This study utilizes XFEM to investigate the evolution of hydraulic fractures, specifically focusing on the influence of crack geometry, including crack length and initial orientation, on fracture behaviour. Unlike previous works that have primarily aimed to validate the general applicability of XFEM in hydraulic fracturing simulations, the present research centers on understanding how variations in crack geometry affect stress intensity factors (SIFs), displacement fields, and fracture propagation paths. Rather than emphasizing XFEM’s well-known numerical strengths, this study highlights its capacity to capture complex fracture-rock interactions within low-permeability and geologically heterogeneous formations. The XFEM framework enables a detailed examination of fluid-driven crack growth under varying mechanical and geometrical conditions. Results demonstrate that increasing crack length leads to higher SIFs and displacement magnitudes, promoting faster fracture propagation. Furthermore, the initial crack angle significantly alters propagation trajectories, with cracks showing a tendency to reorient toward directions of maximum stress concentration. These findings reveal key insights into fracture mechanics in unconventional settings and underscore the complex interplay between crack geometry, stress distribution, and hydraulic forces. Overall, the study confirms XFEM’s potential as a reliable and accurate modeling tool for optimizing hydraulic fracturing design and enhancing recovery efficiency in unconventional reservoirs. Future research should incorporate thermal effects on fracture behaviour, as temperature variations can significantly influence stress fields, material properties, and crack growth in deep subsurface conditions.روش اجزای محدود توسعهیافته (XFEM) یک روش عددی قدرتمند برای شبیهسازی شروع و گسترش ترک بهویژه در مخازن نامتعارف هیدروکربنی مانند شیل و سازندهای گاز چگال (tight gas) است. این مطالعه از روش XFEM برای بررسی فرایند گسترش ترکهای هیدرولیکی استفاده میکند و بهطور خاص بر تأثیر هندسه ترک، از جمله طول و زاویه اولیه آن، بر رفتار شکست تمرکز دارد. برخلاف مطالعات قبلی که عمدتاً به اعتبارسنجی قابلیت کلی XFEM در شبیهسازی شکست هیدرولیکی پرداختهاند، پژوهش حاضر به درک تأثیر تغییرات هندسی ترک بر ضرایب شدت تنش (SIF)، میدان جابجایی و مسیر گسترش ترک متمرکز است. در این تحقیق بهجای تأکید بر مزایای عددی شناختهشده XFEM، توانایی این روش در مدلسازی برهمکنشهای پیچیده بین ترک و سنگ در محیطهای ناهمگن و با تراوایی پایین مورد توجه قرار گرفته است. چارچوب XFEM امکان بررسی دقیق رشد ترکهای ناشی از فشار سیال تحت شرایط مختلف مکانیکی و هندسی را فراهم میکند. نتایج نشان میدهند که افزایش طول ترک منجر به افزایش ضرایب شدت تنش و مقادیر جابجایی شده و در نتیجه، گسترش ترک را تسریع میکند. علاوه بر این، زاویه اولیه ترک تأثیر قابلتوجهی بر مسیرهای گسترش دارد، بهطوریکه ترکها تمایل دارند به سمت نواحی با بیشترین تمرکز تنش تغییر مسیر دهند. این یافتهها بینشهای مهمی درباره مکانیک شکست در محیطهای نامتعارف ارائه میدهند و تعامل پیچیده میان هندسه ترک، توزیع تنش و نیروهای هیدرولیکی را آشکار میسازند. بهطور کلی، این مطالعه توان بالقوه XFEM را بهعنوان یک ابزار مدلسازی دقیق و قابلاعتماد برای بهینهسازی طراحی شکست هیدرولیکی و افزایش بهرهوری برداشت از مخازن نامتعارف تأیید میکند. در مطالعات آینده، پیشنهاد میشود تأثیر حرارت (thermal) بر رفتار ترک نیز مدنظر قرار گیرد، چرا که تغییرات دمایی میتوانند بهطور چشمگیری بر میدانهای تنش، ویژگیهای ماده و رشد ترک در شرایط اعماق زمین تأثیرگذار باشند.http://www.irpga-journal.ir/article_247969_86f0d453f001d97475c1dee1426c2491.pdfانجمن ژئومکانیک نفت ایراننشریه ژئومکانیک و ژئوانرژی2538-46518420260220Development of a Machine Learning -Based Framework for Estimating Rate of Penetration in a Hydrocarbon ReservoirDevelopment of a Machine Learning -Based Framework for Estimating Rate of Penetration in a Hydrocarbon Reservoir364624849410.22107/ggj.2025.522778.1252FAاسماعیلقاسمی الموتیDepartment of Mining and Petroleum Engineering, Imam Khomeini International UniversityاندیشهعلیمرادیDepartment of Mining and Petroleum Engineering, Imam Khomeini International UniversityسعیدهسنماریDepartment of Mining and Petroleum Engineering, Imam Khomeini International Universityحسن رضاقاسمی تبارDepartment of Mining, Petroleum and Geophysics; Shahrood University of Technology0000-0002-4195-5300مجیدسجادیانKhazar Oil Companyسجادتالش حسینیDepartment of Mining and Petroleum Engineering, Imam Khomeini International University0009-0008-1720-0574Journal Article20250511The primary objective of this research is to enhance the calculation of the Rate of Penetration (ROP) in one of Iran’s oil fields using Machine Learning (ML) techniques. Given the significance of ROP evaluation in optimizing drilling operations and reducing costs, this study aims to develop an accurate and efficient model for predicting ROP based on geological characteristics and drilling parameters. AI methods are employed to improve prediction accuracy and optimize drilling processes and ultimately reduce the time and costs of drilling operations. The data required for model generation were collected from one of the Iranian oil fields, encompassing lithological and formation properties and drilling parameters. The back-propagation multi-layer deep models trained, tested and validated with real data. The results demonstrated that ML techniques can significantly enhance ROP prediction accuracy leading to improved and more controlled drilling processes. Additionally, these models can reduce drilling time and substantially lower operational costs. Two ML methods, Random Forest (RF) and Support Vector Machines (SVM), were utilized for modeling based on available data. Input parameters for the model include Depth In-Out/Meterage (m), Weight on Bit (WOB) Min-Max, Rotations Per Minute (RPM) Min-Max, Gallons Per Minute (GPM) Min-Max, Pump Pressure On-Bottom Min-Max, Mud Weight In Min-Max and Mud Weight Out Min-Max. The model’s output is the calculated ROP with minimal error.The primary objective of this research is to enhance the calculation of the Rate of Penetration (ROP) in one of Iran’s oil fields using Machine Learning (ML) techniques. Given the significance of ROP evaluation in optimizing drilling operations and reducing costs, this study aims to develop an accurate and efficient model for predicting ROP based on geological characteristics and drilling parameters. AI methods are employed to improve prediction accuracy and optimize drilling processes and ultimately reduce the time and costs of drilling operations. The data required for model generation were collected from one of the Iranian oil fields, encompassing lithological and formation properties and drilling parameters. The back-propagation multi-layer deep models trained, tested and validated with real data. The results demonstrated that ML techniques can significantly enhance ROP prediction accuracy leading to improved and more controlled drilling processes. Additionally, these models can reduce drilling time and substantially lower operational costs. Two ML methods, Random Forest (RF) and Support Vector Machines (SVM), were utilized for modeling based on available data. Input parameters for the model include Depth In-Out/Meterage (m), Weight on Bit (WOB) Min-Max, Rotations Per Minute (RPM) Min-Max, Gallons Per Minute (GPM) Min-Max, Pump Pressure On-Bottom Min-Max, Mud Weight In Min-Max and Mud Weight Out Min-Max. The model’s output is the calculated ROP with minimal error.http://www.irpga-journal.ir/article_248494_4b79b207928dc696be75f8a3242afa2b.pdfانجمن ژئومکانیک نفت ایراننشریه ژئومکانیک و ژئوانرژی2538-46518420260220A closed-form screening criterion for stress-dependent permeability effects on waterflood performanceA closed-form screening criterion for stress-dependent permeability effects on waterflood performance475725126710.22107/ggj.2026.594380.1268FAبهنامابراهیمیبلوار کشاورز، بعد از خیابان فلسطین، کوچه رویان، پلاک 40009-0009-3810-5362احسانطاهریدانشگاه تربیت مدرس0000-0003-3171-8333Journal Article20250729Coupled flow–geomechanics simulation is expensive, and it needs to be known whether it changes the forecast. For single-phase flow to a single well the answer has been known since the 1980s: an exponential dependence of permeability on effective stress reduces the problem to one dimensionless group. Whether this extends to two-phase displacement in heterogeneous rock has not been examined. This is tested on a field-scale quarter five-spot, in which a stress-dependent permeability is imposed through a uniaxial-strain poroelastic closure and swept over one homogeneous and four heterogeneous log-normal fields, in 104 simulations. At issue is not the constitutive law, assumed alike by simulation and scaling, but whether the geometric cancellation behind the single-well result is preserved under heterogeneity and a second mobile phase. It is shown to be preserved. The ratio of coupled to uncoupled injector-to-producer pressure difference is collapsed onto a closed-form curve with a median error below one per cent, even though the uncoupled difference itself is shifted by a factor of four across the heterogeneity levels tested; the collapse is insensitive to grid resolution, the pressure solver, and whether permeability is tied to effective stress directly or through porosity. The displacement measures are barely affected: although permeability is varied by an order of magnitude and injection pressure is reduced by up to three quarters, breakthrough time and recovery factor shift by less than one per cent. Under a prescribed rate, the pressure field is rescaled by the coupling without the flow being redirected, and the same dimensionless group is shown to govern a well held at fixed pressure, where the coupling appears as a gain in injectivity rather than as a drop in pressure. Inverting the scaling yields a screening rule that costs nothing to apply and determines whether a coupled simulation is required.Coupled flow–geomechanics simulation is expensive, and it needs to be known whether it changes the forecast. For single-phase flow to a single well the answer has been known since the 1980s: an exponential dependence of permeability on effective stress reduces the problem to one dimensionless group. Whether this extends to two-phase displacement in heterogeneous rock has not been examined. This is tested on a field-scale quarter five-spot, in which a stress-dependent permeability is imposed through a uniaxial-strain poroelastic closure and swept over one homogeneous and four heterogeneous log-normal fields, in 104 simulations. At issue is not the constitutive law, assumed alike by simulation and scaling, but whether the geometric cancellation behind the single-well result is preserved under heterogeneity and a second mobile phase. It is shown to be preserved. The ratio of coupled to uncoupled injector-to-producer pressure difference is collapsed onto a closed-form curve with a median error below one per cent, even though the uncoupled difference itself is shifted by a factor of four across the heterogeneity levels tested; the collapse is insensitive to grid resolution, the pressure solver, and whether permeability is tied to effective stress directly or through porosity. The displacement measures are barely affected: although permeability is varied by an order of magnitude and injection pressure is reduced by up to three quarters, breakthrough time and recovery factor shift by less than one per cent. Under a prescribed rate, the pressure field is rescaled by the coupling without the flow being redirected, and the same dimensionless group is shown to govern a well held at fixed pressure, where the coupling appears as a gain in injectivity rather than as a drop in pressure. Inverting the scaling yields a screening rule that costs nothing to apply and determines whether a coupled simulation is required.http://www.irpga-journal.ir/article_251267_0533b86119b2f6902b0f21721ac12a06.pdfانجمن ژئومکانیک نفت ایراننشریه ژئومکانیک و ژئوانرژی2538-46518420260220Thermo-Mechanical Behavior of Graphene-Reinforced Auxetic Sandwich Beams as an Equivalent Model for Oil-Well Casing Subjected to Geo mechanical Loadingمدلسازی تحلیلی رفتار خمش و کمانش تیر ساندویچی با هسته آگزتیک و رویههای کامپوزیتی تقویتشده با نانوصفحات گرافنی تحت بارگذاری ژئومکانیکی و حرارتی با کاربرد در لوله جداری چاههای نفت587425126210.22107/ggj.2026.594483.1269FAآرمینخدامیگروه فنی و مهندسی-دانشکده مکانیک-دانشگاه تربیت مدرس - تهران-ایراناکبرعلی بیگلوگروه فنی مهندسی ، دانشکده مکانیک ، دانشگاه تربیت مدرس،تهران،ایرانJournal Article20250730Oil-well casing structures operating in deep underground environments are simultaneously subjected to high geomechanical stresses and elevated temperatures, which may significantly reduce their structural stability and service life. This study presents a unified analytical framework for evaluating the thermo-mechanical behavior of advanced oil-well casing systems using an equivalent graphene nanoplatelet-reinforced composite (GPLRC) sandwich beam with a re-entrant auxetic core. The proposed model is formulated based on Reddy’s third-order shear deformation theory, Hamilton’s principle, and the Navier solution to investigate the bending and buckling responses under coupled geomechanical and thermal loading conditions. Temperature-dependent material properties, effective in-situ geomechanical stresses, and thermally induced compressive forces are incorporated into the formulation to realistically represent downhole operating conditions. A comprehensive parametric study is conducted to examine the influences of GPL volume fraction, GPL distribution pattern, auxetic cell angle, geomechanical loading, and temperature on the structural performance of the equivalent casing model. The results demonstrate that increasing the GPL content from 0 to 1% reduces the mid-span deflection by approximately 68% and increases the critical buckling load by about 212%, while the FG-X distribution provides the best overall structural performance. The proposed configuration reaches the adopted linear-response limit at an effective external pressure of approximately 48.5 MPa, and thermo-mechanical buckling occurs at a critical temperature rise of about 242 °C for the highest investigated preload ratio. The findings demonstrate that the combined use of GPL-reinforced face sheets and a re-entrant auxetic core can significantly enhance the stiffness and global stability characteristics of the proposed equivalent sandwich-beam model. Furthermore, the developed analytical framework provides a computationally efficient reduced-order tool for preliminary parametric assessment of casing-related global response modes under representative high-pressure and high-temperature downhole conditions.سازههای لوله جداری چاههای نفت در اعماق زمین بهطور همزمان تحت تأثیر تنشهای بالای ژئومکانیکی، فشارهای خارجی و دماهای زیاد قرار دارند که این شرایط میتواند موجب کاهش پایداری سازهای، افزایش تغییرشکل و کاهش عمر بهرهبرداری آنها شود. در این پژوهش، یک چارچوب تحلیلی یکپارچه برای ارزیابی رفتار ترمومکانیکی این سازهها ارائه شده است. بدین منظور، لوله جداری بهصورت معادل با یک تیر ساندویچی از جنس کامپوزیت تقویتشده با نانوصفحات گرافنی (GPLRC) و دارای هسته آگزتیک بازگشتی مدلسازی شده است. فرمولبندی مدل بر پایه نظریه تغییرشکل برشی مرتبه سوم ردی، اصل همیلتون و روش حل ناویه انجام شده و رفتار خمشی و کمانشی سازه تحت بارگذاری همزمان حرارتی و ژئومکانیکی بررسی شده است. همچنین، اثر خواص وابسته به دما، تنشهای ژئومکانیکی برجا و نیروهای فشاری ناشی از افزایش دما در مدل لحاظ شده تا شرایط واقعی درون چاه شبیهسازی شود. در ادامه، تأثیر پارامترهایی نظیر کسر حجمی نانوصفحات گرافنی، الگوی توزیع آنها، زاویه سلول آگزتیک، بارگذاری ژئومکانیکی و دما بر عملکرد سازهای بررسی شده است. نتایج نشان میدهد افزایش مقدار نانوصفحات گرافنی از صفر به ۱ درصد، خیز میانی سازه را حدود ۶۸ درصد کاهش داده و بار بحرانی کمانش را حدود ۲۱۲ درصد افزایش میدهد. همچنین، الگوی توزیع FG-X بهترین عملکرد سازهای را در میان الگوهای بررسیشده ارائه میکند. بر اساس نتایج، ترکیب لایههای رویی تقویتشده با نانوصفحات گرافنی و هسته آگزتیک، راهکاری سبک، مقاوم و مؤثر برای افزایش سختی، پایداری و عملکرد ترمومکانیکی لولههای جداری چاه نفت بوده و چارچوب تحلیلی ارائهشده میتواند بهعنوان ابزاری کارآمد در طراحی و بهینهسازی اولیه این سازهها در شرایط فشار و دمای بالا مورد استفاده قرار گیرد.http://www.irpga-journal.ir/article_251262_f2b094aec4e09cf4bf8a6478f5c141fa.pdfانجمن ژئومکانیک نفت ایراننشریه ژئومکانیک و ژئوانرژی2538-46518420260220Energy piles: behavior and geoenvironmental challengesEnergy piles: behavior and geoenvironmental challenges759725237710.22107/ggj.2026.596200.1271FAحسنقاسم زادهدانشگاه صنعتی خواجه نصیرالدین طوسی0000-0001-6267-9619افسانهعلیوردیدانشگاه صنعتی خواجه نصیرالدین طوسی0000-0001-6267-9619Journal Article20250808Energy piles , also referred to as thermal piles,. which provide a sustainable energy source, represent an interdisciplinary advancement in the fields of geotechnical and environmental engineering, and their application has increased rapidly over the past decades. Due to the growing importance of this topic, numerous studies have been conducted on energy piles, and several review papers have addressed different aspects of their behavior. However, no comprehensive study has yet been reported that brings together recent advances in methods for evaluating the displacement behavior of energy piles in both saturated and unsaturated soils. To date, much of the existing research has focused on the thermal behavior of energy piles, while the mechanical and chemical aspects have often been neglected. This article provides a comprehensive evaluation of the findings of previous studies and highlights areas requiring further investigation. In particular, the effects of several factors, including soil saturation, loading mechanisms, the mechanical and thermal properties of the soil, and pile configuration, on the displacement behavior of energy piles are investigated. Moreover, the long-term performance of energy piles is discussed, and a comprehensive example of an element subjected to thermal and chemical loading is presented, suggesting a novel direction for future researchEnergy piles , also referred to as thermal piles,, which provide a sustainable energy source, represent an interdisciplinary advancement in the fields of geotechnical and environmental engineering, and their application has increased rapidly over the past decades. Due to the growing importance of this topic, numerous studies have been conducted on energy piles, and several review papers have addressed different aspects of their behavior. However, no comprehensive study has yet been reported that brings together recent advances in methods for evaluating the displacement behavior of energy piles in both saturated and unsaturated soils. To date, much of the existing research has focused on the thermal behavior of energy piles, while the mechanical and chemical aspects have often been neglected. This article provides a comprehensive evaluation of the findings of previous studies and highlights areas requiring further investigation. In particular, the effects of several factors, including soil saturation, loading mechanisms, the mechanical and thermal properties of the soil, and pile configuration, on the displacement behavior of energy piles are investigated. Moreover, the long-term performance of energy piles is discussed, and a comprehensive example of an element subjected to thermal and chemical loading is presented, suggesting a novel direction for future researchhttp://www.irpga-journal.ir/article_252377_e3c8364b131871e4232209283684f44b.pdf