تحلیل پایداری چاه با استفاده از منحنی اندرکنش زمین و معیار مور-کولمب | |
| روش های تحلیلی و عددی در مهندسی معدن | |
| دوره 15، شماره 42، فروردین 1404، صفحه 69-76 اصل مقاله (591.57 K) | |
| نوع مقاله: مقاله پژوهشی | |
| شناسه دیجیتال (DOI): 10.22034/anm.2023.20594.1609 | |
| نویسندگان | |
| امیرمحمد احمری؛ ابوالفضل عبدالهی پور* ؛ علیرضا کارگر | |
| دانشکده مهندسی معدن، دانشکدگان فنی، دانشگاه تهران، تهران، ایران | |
| چکیده | |
| امروزه با افزایش نیاز بشر به تأمین انرژی و مشتقات نفتی، استخراج این ماده روزبهروز در حال افزایش است. بااینوجود مخازنی که ازنظر عملیات حفاری و پایداری چاه پیچیدگی و مشکلات اندکی داشتند، در حال اتمام هستند. مهندسان برای پاسخ به این نیاز باید به استخراج منابعی که دارای پیچیدگی و مشکلات بیشتری در حفاری و پایداری نسبت به قبل هستند بپردازند. لذا مبحث پایداری چاه، وزن بهینه و پنجره ایمن سیال حفاری بیشازپیش مورد اهمیت قرار میگیرد. در این پژوهش با تعمیم و اصلاح منحنی اندرکنش زمین که یکی از مهمترین روشها در تحلیل پایداری فضاهای زیرزمینی است، به تحلیل پایداری چاه و انتخاب وزن بهینه سیال حفاری با استفاده از روش حل تحلیلی و عددی پرداخته میشود. در ابتدا منحنی اندرکنش زمین برای پنج حفره دایرهای شکل در میدان تنشهای هیدرواستاتیک و ناهمسانگرد رسم شده و تأثیر پارامترهایی همچون فشار منفذی، نسبتهای مختلف تنشهای افقی به قائم و شعاع حفره روی منحنی اندرکنش زمین برسی میشود. مشخص شد تغییرات این پارامترها با میزان همگرایی دیواره حفره رابطه مستقیم داشته و با افزایش آنها میزان همگرایی دیواره حفره افزایش مییابد. سپس با استفاده از روابط تحلیلی مور-کلمب و روش منحنی اندرکنش زمین در مدلسازی عددی تفاضل محدود، حدود پنجره ایمن سیال حفاری محاسبه گردید. طبق نتایج بهدستآمده در روش عددی با استفاده از منحنی اندرکنش زمین حد پایین و بالای فشار سیال حفاری به ترتیب کمتر و بیشتر از حد پایین و بالای فشار سیال حفاری با استفاده از روش تحلیلی مور-کلمب بوده و روش عددی مبتنی بر منحنی اندرکنش زمین پنجره ایمن بزرگتری نسبت به روش تحلیلی مور-کلمب ارائه میدهد. | |
| کلیدواژهها | |
| ناپایداری چاه؛ منحنی اندرکنش زمین؛ پنجره گِل؛ معیار گسیختگی | |
| عنوان مقاله [English] | |
| Wellbore Stability Analysis Using Ground Reaction Curve and Mohr-Coulomb Failure Criterion | |
| نویسندگان [English] | |
| Amir Mohammad Ahmari؛ Abolfazl Abdollahipour؛ Alireza Kargar | |
| Dept. of Mining Engineering, Colleges of Technology, University of Tehran, Tehran, Iran | |
| چکیده [English] | |
| Summary This research adapts the ground reaction curve (GRC) method, traditionally used in tunnel engineering, to analyze wellbore stability and determine the optimal drilling fluid weight in oil and gas operations. The objectives are to assess wellbore stability under varying conditions and establish a safe drilling fluid pressure window. The methodology employs analytical solutions based on the Mohr-Coulomb failure criterion and numerical modeling using FLAC software. Results demonstrate that parameters such as pore pressure, in-situ stress ratios, and wellbore radius influence wellbore convergence, with the numerical GRC method providing a larger safe drilling fluid pressure window compared to the analytical approach, potentially enhancing drilling efficiency and reducing operational risks. Introduction Wellbore stability is increasingly critical in the oil and gas industry as drilling operations target complex geological formations to meet rising energy demands. Conventional analytical methods for determining safe drilling fluid weights often rely on simplifying assumptions that may not fully address the challenges posed by these environments. This study introduces a novel approach by adapting the ground reaction curve (GRC), a concept from tunnel engineering, to wellbore stability analysis. The GRC relates internal pressure to radial displacement, offering a framework to evaluate rock mass behavior under varying conditions. Pertinent literature highlights diverse approaches to wellbore stability, including elastoplastic and poroelastic models, and failure criteria such as Mohr-Coulomb, Mogi-Coulomb, and Hoek-Brown [1-2]. Building on these foundations, this research employs two methods: an analytical approach using the Mohr-Coulomb criterion with Kirsch equations to calculate stress distributions and critical pressures, and a numerical approach using FLAC software to simulate wellbore excavation and generate the GRC. The study investigates the effects of pore pressure, stress anisotropy, and wellbore radius on stability. The main findings indicate that the numerical method yields a broader safe drilling fluid pressure window, offering potential operational advantages over the analytical method. Methodology and Approaches The methodology integrates analytical and numerical techniques to assess wellbore stability. Analytically, stress distributions around the wellbore are computed using the Kirsch equations, which describe radial and tangential stresses as functions of drilling fluid pressure, in-situ stresses, and Poisson’s ratio. The Mohr-Coulomb failure criterion is then applied to determine the minimum pressure preventing shear failure (collapse) and the maximum pressure avoiding tensile failure (fracturing), establishing the safe pressure window. Numerically, the FLAC software (version 8) simulates wellbore excavation in a two-dimensional model under hydrostatic and anisotropic stress fields. The GRC is generated by monitoring radial displacement as internal pressure varies. The lower limit of the safe pressure window is identified when the wellbore stabilizes (e.g., at 75% of in-situ stress in the hydrostatic case), while the upper limit is determined by minimizing the plastic zone around the wellbore (e.g., at 42 MPa). The study also examines the sensitivity of the GRC to pore pressure, stress ratios, and wellbore radius, with parameters detailed in the original paper’s Table 1. This dual approach provides a comprehensive stability analysis, with sufficient detail to replicate the methods or refer to cited works [3-4]. Results and Conclusions The GRC analysis shows that increased pore pressure, stress anisotropy, and wellbore radius amplify convergence. Table 1 compares the safe drilling fluid pressure windows from both methods in a hydrostatic field (σH = σh = 30 MPa). The numerical GRC method consistently provides a larger window across conditions, enhancing drilling flexibility. Fig. 1 visually contrasts these windows, confirming that the numerical GRC method generally provides a larger safe range across conditions, enhancing drilling flexibility. This principle suggests that integrating displacement-based numerical analysis with failure-based analytical methods improves stability assessment. An exception occurs in specific hydrostatic cases where the numerical window narrows slightly, possibly due to differing criteria emphasis. Theoretically, this approach refines wellbore mechanics understanding; practically, it suggests cost and risk reductions. Validation with field data remains necessary. The study concludes that the GRC method is a promising tool for optimizing drilling fluid design, recommending further testing across diverse formations. | |
| کلیدواژهها [English] | |
| well instability, ground reaction curve, mud window, Failure Criterion | |
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[1] González-Cao J, Varas F, Bastante FG, Alejano LR. Ground reaction curves for circular excavations in non-homogeneous, axisymmetric strain-softening rock masses. Journal of Rock Mechanics and Geotechnical Engineering. 2013 Dec 1;5(6):431-42.
[2] Amberg F. For a correct interpretation of ground reaction curves. In12th ISRM Congress 2011 Oct 16. OnePetro.
[3] Fenner R. Untersuchungen zur erkenntnis des gebirgsdrucks. (No Title). 1938.
[4] Pacher F. Deformationsmessungen im Versuchsstollen als Mittel zur Erforschung des Gebirgsverhaltens und zur Bemessung des Ausbaues. In Principles in the Field of Geomechanics: 14th Symposium of the Austrian Regional Group (if) of the International Society for Rock Mechanics Salzburg, 27. und 28. September 1964 (pp. 149-161). Springer Berlin Heidelberg.
[5] Carranza-Torres C, Fairhurst C. The elasto-plastic response of underground excavations in rock masses that satisfy the Hoek–Brown failure criterion. International Journal of Rock Mechanics and Mining Sciences. 1999 Sep 1;36(6):777-809.
[6] Panet M. Analysis of convergence behind the face of a tunnel.
[7] Duncan Fama ME. Numerical modeling of yield zones in weak rock.
[8] Guan Z, Jiang Y, Tanabasi Y. Ground reaction analyses in conventional tunnelling excavation. Tunnelling and Underground Space Technology. 2007 Mar 1;22(2):230-7.
[9] Alejano LR, Rodriguez-Dono A, Alonso E, Manín GF. Ground reaction curves for tunnels excavated in different quality rock masses showing several types of post-failure behaviour. Tunnelling and Underground Space Technology. 2009 Nov 1;24(6):689-705.
[10] Lee YK, Pietruszczak S. A new numerical procedure for elasto-plastic analysis of a circular opening excavated in a strain-softening rock mass. Tunnelling and Underground Space Technology. 2008 Sep 1;23(5):588-99.
[11] Wang S, Yin X, Tang H, Ge X. A new approach for analyzing circular tunnel in strain-softening rock masses. International Journal of Rock Mechanics and Mining Sciences. 2010 Jan 1;47(1):170.8
[12] Zhang C, Feng XT, Zhou H, Qiu S, Wu W. Case histories of four extremely intense rockbursts in deep tunnels. Rock mechanics and rock engineering. 2012 May; 45:275-88.
[13] Boness NL, Zoback MD. Mapping stress and structurally controlled crustal shear velocity anisotropy in California. Geology. 2006 Oct 1;34(10):825-8.
[14] Aadnøy BS, Belayneh M. Elasto-plastic fracturing model for wellbore stability using non-penetrating fluids. Journal of Petroleum Science and Engineering. 2004 Dec 15;45(3-4):179-92.
[15] Al-Ajmi AM, Zimmerman RW. Stability analysis of vertical boreholes using the Mogi–Coulomb failure criterion. International Journal of Rock Mechanics and Mining Sciences. 2006 Dec 1;43(8):1200-11.
[16] Al-Ajmi AM, Zimmerman RW. A new well path optimization model for increased mechanical borehole stability. Journal of Petroleum Science and Engineering. 2009 Nov 1;69(1-2):53-62.
[17] Zhang L, Cao P, Radha KC. Evaluation of rock strength criteria for wellbore stability analysis. International journal of rock mechanics and mining sciences. 2010 Dec 1;47(8):1304-16.
[18] Gholami R, Moradzadeh A, Rasouli V, Hanachi J. Practical application of failure criteria in determining safe mud weight windows in drilling operations. Journal of Rock Mechanics and Geotechnical Engineering. 2014 Feb 1;6(1):13-25.
[19] Maleki S, Gholami R, Rasouli V, Moradzadeh A, Riabi RG, Sadaghzadeh F. Comparison of different failure criteria in prediction of safe mud weigh window in drilling practice. Earth-Science Reviews. 2014 Sep 1;136:36-58.
[20] Najibi AR, Ghafoori M, Lashkaripour GR, Asef MR. Reservoir geomechanical modeling: In-situ stress, pore pressure, and mud design. Journal of Petroleum Science and Engineering. 2017 Mar 1;151:31-9.
[21] Andrieux P, Detournay C, Hart R. FLAC and numerical modeling in geomechanics. Brummer RK, editor. Balkema; 2003.
[22] Fjær E, Holt RM, Horsrud P, Raaen AM. Petroleum related rock mechanics. Elsevier; 2021 Dec 8.
[23] Gholami R, Moradzadeh A, Rasouli V, Hanachi J. Practical application of failure criteria in determining safe mud weight windows in drilling operations. Journal of Rock Mechanics and Geotechnical Engineering. 2014 Feb 1;6(1):13-25.
[24] Abdollahipour, A., & Fatehi-Marji, M. Numerical modeling of borehole breakouts formation in various stress fields using a Higher-Order Displacement Discontinuity Method (HODDM). Journal of Petroleum Geomechanics, 2022, 4(3), 1–18.
[25] Abdollahipour, A., Kargar, A., & Fatehi-Marji, M. Numerical modeling of effect of Anderson’s stress regimes on volume of sand production in oil wellbores. Analytical and Numerical Methods in Mining Engineering, 2023, 13(25), 31–38.
[26] Amirkhani, M., & Abdollahipour, A. Sensitivity Analysis and determination of the most important affecting parameters in stability of oil wellbores based on numerical modeling in Phase2. Journal of Analytical and Numerical Methods in Mining Engineering, 2024, 14(38).
[27] Heydari, M., Aghakhani Emamqeysi, M. R., & Sanei, M. Finite element analysis of wellbore stability and optimum drilling direction and applying NYZA method for a safe mud weight window. Journal of Analytical and Numerical Methods in Mining Engineering, 2022, 11(29).
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