Systematic fractures analysis using image logs and complementary methods in the Marun Oilfield, SW Iran

Document Type: Research Paper

Authors

1 Department Geology, Chamran, University, Ahvaz, Iran

2 National South Iranian Oil Company (NISOC), Studies office, Ahvaz, Iran

Abstract

Fractures are considered as one of the important structures in fractured reservoirs due to their effect on fluid currents and reservoir
parameters such as porosity and permeability. Fracture parameters can only be directly calculated with core and image logs. Cores have
serious limitations, so image logs are the best method. The aim of this study is the systematic fractures analysis of the Asmari
Formation in the Marun field as one of the giant oilfields in world. The main objectives of image logs were evaluating structural dip,
characterizing natural fractures and field structure heterogeneity, and finally correlating the results with complimentary methods such
as Velocity Deviation Log (VDL), Repeat Formation Test (RFT), mud lost data, and isodip map in the carbonate Asmari Formation.
Generally, electric and ultrasonic imaging tools record vast amounts of high-resolution data. This enables geoscientists to describe in
detail the structural fracture networks. The results indicate that the highest fracture density is in the zones 1, 20, and 30 of the Asmari
reservoir that show high correlation with VDL and mud lost data. Image logs also show a range of bedding dips from 20˚ in the
northern limb to 30˚ in the southern limb with strikes ranging from 10˚ to 270˚N. Regarding the general pattern of fractures, it is
evident that they are related to the folding and are classified mainly as longitudinal, transverse, and oblique. The longitudinal pattern is
dominant and often forms open fractures. They are characterized by N50W-S50E and mainly observed in the upper Asmari zones.
Moreover, to find the vertical relation of the layer and fractures, RFT data were used. The findings revealed the presence of a vertical
relation in the upper horizons of the reservoir, especially in the eastern section due to the high fracture density.

Keywords


Article Title [Persian]

تحلیل سیستماتیک شگستگی های میدان مارون با استفاده از نمودارهای تصویرگر و روش های تکمیلی

Authors [Persian]

  • ایمان زحمت کش 1
  • قاسم عقلی 1
  • روح انگیز محمدیان 2
2 شرکت ملی مناطق نفتخیز جنوب
Abstract [Persian]

شکستگی ها به دلیل تاثیر بر پارامترهای مخزنی مانند تخلخل و تراوایی، یکی از مهمترین پارامترها در مخازن شکسته هستند. شکستگی‌ها تنها با استفاده از مغزه و نمودارهای تصویرگر به صورت مستقیم مطالعه می‌شوند. به دلیل محدودیت‌های استفاده ازمغزه، نمودارهای تصویرگر بهترین ابزارها می‌باشند. هدف این مقاله بررسی سیستماتیک شکستگی‌های مخزن آسماری میدان نفتی مارون به عنوان یکی از بزرگترین مخازن نفتی جهان است. در این مطالعه، از نمودارهای تصویرگر برای تفسیر شکستگی‌ها و هتروژنی مخزن استفاده شد و در نهایت نتایج حاصل با سایر روش‌های تکمیلی مانند نمودار انحراف سرعت، لایه آزمایی مکرر چاه، هرزروی گل و نقشه‌های هم‌شیب مقایسه شدند. به طور کلی نمودارهای تصویرگر حجم زیادی از اطلاعات با قدرت تفکیک بالا را ذخیره می‌کنند که این مهم به مفسران کمک شایانی می‌کند. نتایج این تحقیق تمرکز بالای شکستگی‌ها را در زون‌های 1، 20 و 30 نشان می‌دهد که انطباق بالایی با نتایج نمودار انحراف سرعت و هرزروی گل حفاری دارد. نمودارهای تصویرگر میانگین شیب لایه‌بندی را از 20 درجه در یال شمالی تا 30 درجه در یال جنوبی با امتداد 270 درجه از شمال نشان می‌دهد. به طور کلی شکستگی‌های این میدان از نوع مرتبط با چین می‌باشند که به سه دسته طولی، عرضی و مورب تقسیم می‌شوند که نوع طولی غالب، و بیشتر شکستگی‌های باز را شامل می‌شود. در این مطالعه، داده‌های چاه آزمایی مکرر برای بررسی ارتباط بین لایه‌ها و شکستگی‌ها استفاده شدند. نتایج حاصله بیشترین ارتباط بین لایه‌ها را را در قسمت شرقی میدان نشان می‌دهد که دلیل آن تمرکز بالای شکستگی‌ها در این قسمت میدان است.

Keywords [Persian]

  • مخزن آسماری
  • متدهای تکمیلی
  • تحلیل شکستگی
  • نمودارهای تصویرگر
  • میدان مارون
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Volume 5, Issue 2
Summer and Autumn 2015
Pages 139-150
  • Receive Date: 05 June 2015
  • Revise Date: 20 November 2015
  • Accept Date: 25 November 2015