نویسندگان

1 ، مربی پژوهشی ، پژوهشکده علوم زمین پژوهشگاه صنعت نفت تهران

2 مربی پژوهشی، پژوهشکده علوم زمین پژوهشگاه صنعت نفت تهران

چکیده

 
سازند سروک به سن کرتاسه (آلبین-تورونین)، در میدان نفتی آزادگان در جنوب غرب ایران از توالی ضخیمی از نهشته های کربناته تشکیل شده است. تلفیق مطالعات ماکرو- میکروسکوپی با نشانگرهای لرزه ای نشان می دهد که افق مخزنی بخش بالایی سازند سروک در میدان مورد مطالعه از 4 رخساره رسوبی تشکیل شده است. این رخساره ها که شامل (1) وکستون تا پکستون الیگوستجینیددار، (2) پکستون تا وکستون بایوکلاستی/اکینوئیدی ، (3) باندستون بایوکلاستی/رودیستی و (4) نهشته های کربناته پرکننده کانال می باشند، به ترتیب، در بخش عمیق دریای باز، بخش کم عمق دریای باز، برآمدگی یا سد کربناته و کانال نهشته شده اند. مقایسه رخساره های مذکور با نهشته های کربناته مشابه در نقاط دیگر نشان دهنده رسوبگذاری در یک رمپ کربناته می باشد. خارج شدن بخشی از پلاتفرم کربناته سازند سروک در اواخر سنومانین سبب گسترش نهشته های کربناته کانالی در منطقه مورد مطالعه شده است. کیفیت مخزنی بخش بالایی سازند سروک ارتباط نزدیکی با رخساره های رسوبی دارد به نحوی که عوامل دیاژنزی موثر بر تخلخل و تراوایی سازند نیز توسط رخساره کنترل شده است. رخساره های گل- پشتیبان بخش عمیق دریای باز (رخساره 1) به دلیل دانه ریز بودن و عدم تاثیر فرآیندهای دیاژنزی از تخلخل و تراوایی پائینی برخوردارند. در حالیکه رخساره های دانه–پشتیبان بخش های کم عمق تر دریای باز و برآمدگی های کربناته (رخساره های 2 و 3) بدلیل وجود فضاهای خالی بین دانه ای اولیه و تاثیر انحلال از کیفیت مخزنی نسبتا" بالایی برخوردارند.
این مطالعه بر فرآیندهای دیاژنزی که توسط رخساره های رسوبی کنترل شده و همچنین اهمیت آنها در پیش بینی بهتر توزیع تخلخل و تراوایی در مخازن هیدروکربوری اکتشافی و ازدیاد برداشت تاکید دارد. بنابراین بهتر است چنین مطالعه ای  در سایر میادین نفتی و گازی و حوضه های رسوبی بکار گرفته شود.
 

کلیدواژه‌ها

عنوان مقاله [English]

Linking Depositional Facies to Diagenetic Events and Reservoir Quality of the Upper Sarvak Formation in a giant oil field, SW of Iran

نویسندگان [English]

  • j Honarmand 1
  • I Madahi 2

1 Instructor of Department of Petroleum Geology, R.I.P.I

2 Instructor of Department of Petroleum Geology, R.I.P.I

چکیده [English]

The Cretaceous Sarvak Formation (Albian-Turonian) in the Azadegan oil Field in SW Iran is composed of a thick succession of carbonate deposits. Integrated macro and microscopic studies and seismic attributes show that reservoir interval of the Upper Sarvak Formation in the studied field consists of four depositional facies. These are: (1) Oligosteginid wackestone to packstone, (2) Bioclastic-echinoid packstone to wackestone, (3) Bioclastic-rudist boundstone and (4) Channel-filled carbonate deposits. These facies were deposited in distal open marine, proximal open marine, carbonate buildups/barriers and channel depositional setting, respectively.  The comparison of these facies with the same worldwide carbonate successions show that the Upper Sarvak carbonates deposited on a carbonate ramp. Emergence of some parts of Sarvak carbonate platform at the end of Cenomanian stage resulted in development of channel deposition in the studied area.
Reservoir quality of the Upper Sarvak Formation has good relationship with depositional facies, so that diagenetic controls on porosity and permeability are also facies-controlled. Mud-supported facies belong to distal open marine setting (facies 1) have low porosity and permeability. This is due to fine-grained texture and also lack of diagenetic effects. On the other hand, grain-supported facies belong to proximal open marine and carbonate build up/barrier setting (Facies 2 and 3) have relatively good reservoir quality. This is due to presence of primary interparticle pore spaces and also development of dissolution.
This study highlights the facies-controlled diagenesis and its importance in prediction of the distribution of porosity and permeability ahead of exploration in hydrocarbon reservoirs as well as enhanced recovery. Therefore such study should apply to other oil and gas fields and sedimentary basins.
 
 
 

کلیدواژه‌ها [English]

  • : Facies
  • Diagenesis
  • Reservoir quality
  • Carbonate
  • Filled Channel
  • Sarvak
  • Azadegan


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