بررسی پتانسیل وقوع خودمهاری چاه به عنوان یکی از روش های کنترل فوران در حفاری چاه های آب های عمیق

نوع مقاله : مقاله پژوهشی

نویسندگان

مهندسی نفت-دانشکده نفت-دانشگاه صنعتی امیرکبیر-تهران-ایران

چکیده

کیک به ورود سیالات مخزن به داخل چاه گفته می شود که مشکلات زیادی را حین عملیات حفاری به وجود می آورد. در سازندهای پرفشار با مقاومت استحکامی کم، احتمال وقوع خودمهاری چاه با مکانیزم پل‌زدگی بیشتر خواهد بود. شرایط فروتعادلی که حین وقوع کیک به وجود می‌آید، باعث ناپایداری دیواره چاه شده و ریزش دیواره چاه ممکن است باعث به وجود آمدن پدیده خودمهاری و در نتیجه منجر به کنترل کیک گردد.. در این پژوهش پتانسیل وقوع خودمهاری طبیعی و توانایی آن برای جلوگیری از وقوع فوران، در یکی از چاه‌های آب های عمیق در دریای خزر مورد مطالعه قرار گرفته است. بدین منظور از چند سری شبیه سازی های عددی نیمه کوپل برای ارزیابی پروفایل فشار دیواره چاه و ناپایداری دیواره به عنوان تابعی از‌ زمان در شرایط کیک استفاده شده است. شبیه سازی های انجام شده در یک سناریوی خاص از فوران نشان می‌دهد که قطعات سنگ جدا شده از دیواره چاه در طول وقوع کیک، در درون سیال سازند در حال حرکت، معلق می‌مانند، به گونه ای که احتمال پلاگ شدن چاه و وقوع خود مهاری از طریق تجمع خرده های حفاری در درون چاه کم خواهد بود. از طرف دیگر ورود خرده سنگ های حاصل از ریزش دیواره چاه به داخل چاه باعث افزایش سریع غلظت مواد جامد موجود در درون سیال می شود. به طوری که پس از گذشت زمان مشخصی از وقوع کیک، این غلظت به یک حد بحرانی رسیده و پل‌زدگی مانع از گسترش کیک و تبدیل آن به فوران می شود.

کلیدواژه‌ها

عنوان مقاله [English]

Assesment of self-killing as a blowout control method in deep water wells

نویسندگان [English]

  • Alireza Tayefeh Younesi
  • Mohammad Sabah
  • Mohammad Javad Ameri Shahrabi
Department of petroleum engineering-Amirkabir University of Technology-Tehran-Iran
چکیده [English]

Blowout is the uncontrolled flow of reservoir fluids into the well, which can cause different types of problems during the drilling operations. In high-pressure formations with low rock strengths, it is more likely to occur self-killing through bridging mechanisms. The underbalanced conditions that are induced during developing a kick, leading into sufficient instability in exposed formations such that the borehole bridges over and kick kills itself. In this research, the potential of natural bridging is studied in one of the deep-water wells in the Caspian Sea to figure out whether this natural phenomenon is able to terminate the uncontrolled influxes of formation fluids into the borehole. For the reason, a series of semi-integrated numerical simulators are employed to evaluate wellbore pressure profile and wellbore instability as a function of time under blowout conditions. Applied analyses to a particular blowout scenario indicated that rock fragments falling off the wellbore wall are suspended in the two-phase flow (a mixture of gas and drilling mud) during developing the kick. As a result, cavings settlement is less not probable to plug the wellbore. On the other hand, suspension of rock fragments gradually increases the solid concentration of fluid phase until it hits a critical value at a certain time after the beginning of the kick, thereby bridging occurs before developing the kick into a blowout.

کلیدواژه‌ها [English]

  • Kick
  • Wellbore instability
  • Self-killing
  • Blowout
  • Caspian Sea

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نشریه علمی ژئومکانیک نفت
دوره 5، شماره 2
شهریور 1401
صفحه 17-33

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