تاثیر فرآیندهای دیاژنزی در توزیع واحد‌های مخزنی و غیر مخزنی سازند آسماری در میدان نفتی اهواز (چاه‌های شماره X، Y، Z)

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه زمین‌شناسی، دانشکده علوم زمین، دانشگاه شهید بهشتی، تهران، ایران

2 گروه زمین‌شناسی، اداره زمین‌شناسی مناطق نفت خیز جنوب، اهواز، ایران

چکیده

مقدمه: سازند آسماری در جنوب غربی ایران جوان­ترین و مهم­ترین مخزن هیدروکربنی ایران است. سازند آسماری در میدان نفتی اهواز در چاه­های مورد مطالعه شامل سنگ آهک، دولومیت، سنگ آهک دولومیتی، دولومیت شنی و ماسه سنگ، سیلت سنگ و شیل است. در برخی موارد، رخساره­های مشابه تحت فرآیندهای دیاژنزی مشابهی قرار می­گیرند اما در اکثر مواقع به دلیل تاثیر زیاد فرآیندهای دیاژنزی، توزیع تخلخل-نفوذ کاملاً معکوس می­شود. بنابراین، انجام مطالعات دیاژنز دقیق و بررسی اثرات دیاژنز بر تغییرات و تحولات مخزن در کلیه مطالعات سیستماتیک و بنیادی مخازن کربناته و مخازن هیبریدی ضروری است.
مواد و روش­ها: این مطالعه بر روی چاه­های شماره X،Y  و Z میدان نفتی اهواز انجام شد. در این تحقیق 1100 برش نازک از هسته­های حفاری چاه­های مذکور مورد بررسی قرار گرفت. انواع رخساره­ها و فرآیندهای دیاژنز حاکم بر آنها با استفاده از مطالعات مقطع نازک میکروسکوپی هسته­های مته شناسایی شده است. انواع ریز رخساره­ها براساس روش دانهام نامگذاری شدند. به منظور تشخیص سنگ آهک از دولومیت، تمام مقاطع نازک با محلول قرمز آلیزارین طبق روش دیکسون (1965) رنگ آمیزی شدند. از داده­های دیجیتال چاه و تخلخل (ناشی از آزمایش هسته گاز هلیوم) و نفوذپذیری هسته (ناشی از آزمایش هسته اشباع جیوه) به منظور توزیع واحدهای مختلف (مخزن و غیر مخزن) در چاه­های مورد مطالعه و ترسیم مدل دو بعدی توزیع آنها با استفاده از نرم­افزار Geolog و Excel استفاده شد. میدان با استفاده از واحدهای هیدرولیک جریان در هر نوع سنگ مورد مطالعه قرار گرفت.
نتایج و بحث: اکثر فرآیندهای دیاژنز سازند آسماری در میدان مورد مطالعه در شرایطی رخ داده است که محیط دیاژنز تحت­تأثیر محیط رسوبی قرار گرفته است. انحلال و دولومیتی شدن بیشترین نقش را در افزایش کیفیت مخزن داشته است. این دو فرآیند مهم­ترین فرآیندهای دیاژنتیکی کنترل کننده کیفیت مخزن هستند. دولومیتیزاسیون در مخزن آسماری از فرآیندهای دیاژنتیکی بسیار زودرس و دیررس است که تأثیر دوگانه (سازنده و مخرب) بر کیفیت مخزن سازند آسماری داشته است، بالا بردن کیفیت مخزن در سنگ آهک و در ماسه سنگ ها به صورت سیمان است. سیمان انیدریت مهم­ترین فرآیند دیاژنتیکی است که تأثیر منفی بر کیفیت مخزن دارد. گسترش رخساره­های آواری درشت دانه بهترین رخساره­های مستعد مخزن هستند و فرآیندهای دیاژنز این رخساره­ها عمدتاً متاثر از محیط رسوبی آنها بوده است. در میدان مورد مطالعه، هرچه انبساط جانبی و ضخامت رخساره ماسه سنگی بیشتر باشد، کیفیت مخزن آن بهتر است. سهم شرایط محیطی در کنترل کیفیت مخزن رخساره­های کربناته کمتر از رخساره­های آواری و مختلط است.
نتیجه­ گیری: در بررسی‌ها، هشت واحد جریان هیدرولیک شناسایی شد که بهترین آن‌ها واحدهای جریان هیدرولیک هفتم و هشتم هستند. این واحدهای جریان هیدرولیک مربوط به نوع سنگ ماسه سست است. بدترین واحدهای جریان هیدرولیک 1 و 2 که مربوط به دولومودستون است.

کلیدواژه‌ها

عنوان مقاله [English]

Effect of diagenetic processes on the distribution of reservoir and non-reservoir units in the Asmari Formation, Ahvaz Oilfield (Wells No, X, Y, Z)

نویسندگان [English]

  • nastaran Azadbakht 1
  • Mahboobeh Hosseinibarzi 1
  • Abdolreza Bavi owidi 2
1 Department of Geology, Faculty of earth Siences, Shahid Beheshti University, Tehran, Iran
2 Department of Geology, Geology Department of National Iranian South Oil Company, Ahwaz, Iran
چکیده [English]

Introduction: The Asmari Formation in southwest Iran is the youngest and most important hydrocarbon reservoir in Iran. Asmari Formation in Ahvaz oil field in the studied wells consists of limestone, dolomite, dolomitic limestone, sandy dolomite and sandstone, siltstone and shale. In some cases, similar facies are subjected to similar diagenesis processes, but most of the time due to the high impact of diagenetic processes the porosity-permeability distribution is completely reversed. Therefore, it is necessary to carry out detailed diagenesis studies and investigate the effects of diagenesis on reservoir changes and evolutions in all systematic and fundamental studies of carbonate reservoirs and hybrid reservoirs (Lucia, 2007; Ahr, 2008).
Materials and methods: This study was conducted on wells No. X, Y and Z of Ahvaz oil field. In this study, 1100 thin sections of the drilling cores of the mentioned wells were studied. The types of facies and their governing diagenesis processes have been identified using microscopic thin-section studies of drill cores. Types of microfacies were named based on Dunham's method (Dunham, 1962). In order to distinguish limestone from dolomite, all thin sections were stained with alizarin red solution according to Dickson's method (1965). From digital well and porosity data (resulting from helium gas core testing) and core permeability (resulting from mercury saturation core testing) in order to distribute different units (reservoir and non-reservoir) in the studied wells and drawing the two-dimensional model of their distribution using Geolog, Excel software was used. This field was studied using flow hydraulic units in any rock type.
Results and discussion: Most of the diagenesis processes of the Asmari Formation in the studied field have occurred under conditions where the diagenesis environment was affected by the sedimentary environment. Dissolution and dolomitization, have played the greatest role in increasing the reservoir quality. These two processes, the development of which depended on the sedimentary environment, are the most important diagenetic processes controlling the reservoir quality. Dolomitization in the Asmari reservoir is very early and late diagenetic processes that and has had a dual effect (constructive and destructive) on the reservoir quality of the Asmari Formation, raising the reservoir quality in the limestone and in the Sandstones are in the form of cement Anhydrite cement is the most important diagenetic process with a negative impact on reservoir quality. The expansion of coarse-grained clastic facies are the best reservoir-prone facies, and the diagenesis processes of these facies have been mainly affected by their sedimentary environment. In the studied field, the higher the lateral expansion and thickness of the sandstone facies, the better its reservoir quality. The contribution of environmental conditions in controlling the reservoir quality of carbonate facies is less than that of clastic and mixed facies.
Conclusion: In the survey, eight hydraulic flow units were identified, the best of which are the 7th and 8th hydraulic flow units. These hydraulic flow units correspond to the rock type of loose sand. The worst hydraulic flow units 1 and 2, which corresponds to the dolomudstone rock type.

کلیدواژه‌ها [English]

  • Dolomitization
  • Meteoric Diagenesis
  • Asmari Formation
  • Anhydrite Cement
  • Reservoir Quality

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