فاکتورهای موثر زمین شناسی (رخساره، دیاژنز و تکتونیک) در ویژگی های مخزنی زون C1 مخزن ایلام میدان اهواز

نوع مقاله : مقاله پژوهشی

نویسندگان

گروه حوضه‌های رسوبی و نفت، دانشکده علوم زمین، دانشگاه شهید بهشتی، تهران، ایران

چکیده

سابقه و هدف: اجرای یک پروژه سیلاب زنی نیاز اساسی به مطالعات زمین­ شناسی دارد. این درک نیاز به شناخت فاکتورهای زمین­ شناسی محیط رسوبی، فرایندهای دیاژنتیکی و رفتار گسل­ های مخزنی دارد تا درک مناسبی از خصوصیات سنگ/ آب/ نفت بدست آید. در این مطالعه به دلیل آبی شدن زود هنگام بعضی از چاه ­های تولیدی غرب میدان اهواز و همچنین کاهش فشار مخزنی این ناحیه، تصمیم به انجام عملیات سیلاب زنی گرفته شد که تاکنون چنین عملیاتی در ایران بصورت عملی انجام نشده است.
مواد و روش ها: لذا جهت مطالعه زمین ­شناسی مخزن ایلام اهواز چاه ۱۱۶ از دیدگاه دیاژنز، تغییرات رخساره­ای و تکتونیک توسط ابزار­های میکروسکوپ پلاریزان، میکروسکوپ الکترونی، اطلاعات حاصل از داده ­های مغزه، ارزیابی پتروفیزیکی و مدل مخزنی بررسی گردید.
نتایج و بحث: از دیدگاه رسوب­شناسی، زون C1 مخزن ایلام اهواز از اجزای موجودات میکروسکوپی همی پلاژیک غالبا اولیگوستژینیده در محیط رسوبی دریای باز تشکیل شده است. چنین رخساره­ای که متشکل از گل آهکی میکریتی است، ذاتا باید تخلخل نداشته باشد. اما فرایند دیاژنز متئوریکی قبل از سنگ شدگی باعث افزایش کیفیت مخزنی آن گردیده است. بنحوی که در گستره مخزن شاهد ایجاد مخزنی از نوع آهک گل سفید (chalky) با  تخلخل از ۵  تا  ۲۷ درصد (در ناحیه غربی مخزن از ۱۵ تا ۲۷ درصد تخلخل) و تراوایی کلینکنبرگ ۱ تا ۱۰ میلی دارسی و گاها ۱۰۰ میلی دارسی شده است. همچنین شرایط ایجاد گلوگاه­های خلل و فرجی از ۲۰ تا غالبا چند دهم میکرون را نیز فراهم نموده است. اما دلیل توسعه دیاژنز متئوریکی متفاوت در گستره مخزن را باید در حوادث تکتونیکی زاگرس در دوران کرتاسه دنبال کرد. در دوران کرتاسه  گسل های پی سنگی کششی دوران مزوزوئیک فعالیت مجدد کرده و بر جغرافیای گذشته حوضه تاثیر می ­گذارند. بنحوی که که در امتداد این گسل ­های شمالی-جنوبی در زون C1 مخزن ایلام اهواز شاهد تفاوت در  فرایندهای دیاژنزی ناحیه غربی و نواحی دیگر مخزن هستیم. این تفاوت فرایندهای دیاژنزی کمی قبل از سنگ شدگی رسوب اتفاق افتاده است.
نتیجه گیری: تاثیر مناسب فاکتورهای زمین­ شناسی (رخساره، دیازنز و تکتونیک) شرایطی ایده آلی را برای سیلاب زنی مخزن فراهم کرده است.

کلیدواژه‌ها


عنوان مقاله [English]

Effective geological factors (facies, diagensis and tectonic) for reservoir characterization of Ilam Reservoir zone C1 (Ahwaz oilfield)

نویسندگان [English]

  • Mehdi khoshnood kia
  • Mohammad Hossein Adabi
  • Mahboubeh Hosseini-Barzi
Department of Sedimentary and Petroleum Basins, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran
چکیده [English]

Introduction: Geological studies is essential for running a water flooding project. So, understanding the geological factors is important such as sedimentary environment, diagenetic processes, and reservoir fault behavior to obtain a proper understanding of rock / water / oil properties. In this study, due to the early breakthrough of some wells in west of Ahwaz field as well as the reduction of reservoir pressure in this area, it was decided to perform a water flooding operation, which so far have not been practiced in Iran.
Material and methods: Therefore, geological study have done in Ilam reservoir of AZ-116 in view of diagenesis, facies and tectonic. In this study were used polarizing microscope, electron microscope, core data, petrophysical evaluation and reservoir model.
Results and discussion: From a sedimentological point of view, the C1 zone of the Ilam reservoir of Ahwaz is composed of components of frequently oligostegina hemiplegic microscopic organisms in the sedimentary environment of the open seas. Such a facies, which is composed of calcareous micritic mud, should not inherently have porosity. But the process of meteoric diagenesis before lithification has increased its reservoir quality. Chalky reservoir with porosity of 5% to 27% (in the western part of the reservoir from 15% to 27% porosity) and Klinkenberg permeability of 1 to 10 milli-darcy and sometimes 100 milli-darcy. It also provides conditions for the porethroats from 20 to often several tenths of microns. But the reason for the development of different meteoric diagenesis across the reservoir has to be follwed to the Zagros tectonic events of the Cretaceous period. During the Cretaceous, extensional basement crust of the Mesozoic period reactivated and affected the paleogeography of the basin. So that along these north-south faults in zone C1 of Ilam reservoir of Ahwaz, we see different diagenetic processes in west area incontrast to other part of reservoir, just before litification.
Conclusion: Appropriate impact of geological factors (facies, diagensis and tectonics) has provided ideal conditions for water flooding operation.

کلیدواژه‌ها [English]

  • Diagensis
  • Facies
  • Tectonic
  • Ilam reservoir
  • Ahwaz oilfield
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