مدلسازی فیزیکی چاه‌های نفت هنگام حفاری با استفاده از سلول سه محوری طراحی شده

نوع مقاله : مقاله پژوهشی

نویسندگان

گروه مهندسی معدن، دانشگاه بین المللی امام خمینی (ره)، قزوین، ایران

چکیده

پپیش‌بینی رفتار چاه‌های نفت هنگام حفاری برای جلوگیری از صرف هزینه‌های زیاد و بروز مشکلات پایداری مهم می‌باشد. از جمله مشکلات می‌توان به شکست دیواره‌ی چاه طی حفاری اشاره کرد. برای مدل‌سازی شکست دیواره‌ی چاه‌های نفت هنگام حفاری می‌توان از نمونه‌های استوانه‌ای توخالی جدار ضخیم استفاده کرد. سلول‌های سه محوری مختلفی برای این آزمایش در دنیا وجود دارند. سلول استفاده شده در این تحقیق بر اساس سلول هوک طراحی شده است. از مزایای این سلول می‌توان به قابلیت مدل‌سازی چاه‌های نفت هنگام حفاری و همچنین مدل‌سازی آزمایش شکست هیدرولیکی اشاره کرد. همچنین امکان اندازه‌گیری کرنش مماسی در حفره مرکزی وجود دارد. این امکانات در بیشتر سلول‌های سه‌محوری به طور همزمان وجود ندارند. برای بررسی کارایی این سلول، نمونه‌های استوانه‌ای توخالی جدار ضخیم از گچ و بتن ساخته شد. در این مقاله از دو مسیر تنش مختلف برای اعمال فشار در سلول سه‌محوری استفاده شده است که عبارتند از: Ϭϴ= ϭ1˃ϭr = ϭ2˃Ϭz = ϭ3، Ϭϴ = ϭ1˃ϭz = ϭ2˃Ϭr= ϭ3 =0. نتایج مطالعات در دو مسیر تنش مختلف نشان می‌دهد که در شرایطی که تنش مماسی ناشی از تنش جانبی، تنش حداکثر باشد، شکست در اطراف چاه به‌صورت برشی در دو جهت مخالف دیواره رخ ‌می‌دهد. هم‌چنین وقوع شکست در دیواره نمونه های استوانه ای جدار ضخیم به علت اختلاف تنش جانبی و فشار داخلی است. با افزایش این اختلاف تنش، عمق شکست و گسترش ترک در دیواره نمونه های استوانه ای جدار ضخیم نیز افزایش خواهد یافت. علاوه بر این،  قابل توجه است که در حضور فشار داخلی، عمق شکست یا ناحیه پلاستیک نسبت به عدم حضور آن کاهش می یابد.

کلیدواژه‌ها

عنوان مقاله [English]

Physical Modelling of Oil Wells During Drilling Using Designed Triaxial Cell

نویسندگان [English]

  • M. Hosseini
  • S. Aghayi
Department of Mining Engineering, Imam Khomeini International University, Qazvin, Iran
چکیده [English]

Behavior prediction of oil well during drilling is important to prevent of instability problems and lots of cost spending. One of the problems can be pointed is failure of oil well wall during drilling. Thick-walled hollow cylindrical specimens can be able to modelling failure of oil well wall during drilling. Different triaxial cells exist for this test in world. Cell was used is designed based on Hoek cell. The benefits of this cell are ability of oil well during drilling and hydraulic fracture modelling. Also it is possible to measure the tangential strain in the center hole. This feature simultaneously is absent in most triaxial cells. To evaluate the performance of this cell, gypsum and concrete hollow cylinder specimens were made to modelling of oil wells during drilling. Literature studies and experimental results showed that, depending on the magnitudes of the applied internal pressure, external pressure and axial load, any of the radial, tangential and axial stresses induced in the cylinder considered as minor, intermediate or major principal stress. Hence, in this paper, two different stress conditions were used that consist: ϭϴ = ϭ1 ˃ ϭr = ϭ2 ˃ ϭz = ϭ3،. ϭϴ = ϭ1 ˃ ϭz = ϭ2 ˃ ϭr = ϭ3 =0. Results showed that, in condition that tangential stress induced of lateral stress is maximum stress, shear failure occurred toward at around well. So, failure of wall of thick wall hollow cylinder is caused by the deviator stresses between lateral stress and inner pressure. By increasing deviator stresses, the plastic zone will increase around wall of thick walled hollow cylinder specimens. It is noteworthy that, presence of internal pressure reduces the breakouts propagation.

کلیدواژه‌ها [English]

  • Physical Modelling
  • Triaxial Cell
  • Drilling
  • Oil
  • Well

مراجع

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نشریه مهندسی عمران امیرکبیر
دوره 49، شماره 4
اسفند 1396
صفحه 801-812

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