نشریه ژئومکانیک و ژئوانرژی

نشریه ژئومکانیک و ژئوانرژی

مقایسه تأثیر انواع تخلخل بر خواص الکتریکی سازندهای کربناته دالان و کنگان در بخش مرکزی خلیج فارس

نوع مقاله : مقاله پژوهشی

نویسندگان
1 دانشکده زمین‌شناسی، دانشکدگان علوم، دانشگاه تهران
2 دانشگاه تهران، تهران، ایران
چکیده
تخلخل و انواع آن از مهم‌ترین ویژگی‌های مخازن هستند. مقاومت الکتریکی سازند نیز از ویژگی‌های مهم پتروفیزیکی مخازن است که با استفاده از این ویژگی می‌توان اشباع آب و متعاقباً اشباع هیدروکربور را محاسبه کرد. بنابراین بررسی تأثیر نوع تخلخل بر مقاومت الکتریکی به افزایش درک ارتباط بین ویژگی‌های زمین‌شناسی بر ویژگی‌های پتروفیزیکی و ارزیابی مخازن به ویژه مخازن کربناته کمک خواهد نمود. در این مطالعه از مغزه‌ها، پلاگ‌ها، مقاطع نازک میکروسکوپی و نگار مقاومت الکتریکی یک چاه در سازندهای کربناته-تبخیری دالان و کنگان به ضخامت ۳۴۲.92 متر استفاده شده است. از پلاگ‌های تهیه شده در مجموع ۱۳۶۷ مقطع نازک تهیه شده و ویژگی‌های سنگ‌شناسی، بافت‌های رسوبی، انواع تخلخل‌ها و فرآیندهای دیاژنزی مشخص شد. ضرایب آرچی و اشباع آب برای هر نوع تخلخل با استفاده از داده‌های آزمایشگاهی و چاه‌پیمایی تعیین و محاسبه شد. سپس با استفاده از داده‌های اشباع آب و مقدار تخلخل آزمایشگاهی به بررسی تأثیر و مقایسه هر نوع تخلخل شناسایی شده بر مقاومت الکتریکی پرداخته شد. نتایج نشان داد که مقدار تخلخل تأثیر قابل توجهی بر مقاومت الکتریکی دارد. با افزایش مقدار تخلخل در همه انواع تخلخل‌ها، مقاومت الکتریکی کاهش می‌یابد اما میزان تغییرات و متوسط مقاومت الکتریکی در منافذ گوناگون متفاوت است. تخلخل‌های حفره‌ای با بیشترین مقدار تخلخل مقاومت الکتریکی کمتری دارند در صورتی که تخلخل‌های غیرقابل مشاهده (ریز‌تخلخل‌ها) با کمترین مقدار تخلخل متوسط مقاومت الکتریکی بالاتری نسبت به سایر تخلخل‌های شناسایی شده دارند. علاوه بر این اشباع آب نیز نقش مهمی بر مقاومت الکتریکی دارد و با کاهش اشباع آب در همه تخلخل‌های مورد مطالعه مقاومت الکتریکی افزایش می‌یابد. فرآیندهای دیاژنزی افزاینده تخلخل مانند انحلال در تخلخل‌های قالبی و دولومیتی‌شدن در تخلخل‌های بین‌بلوری منجر به کاهش مقاومت الکتریکی می‌شود و فرآیندهای کاهش‌دهنده تخلخل مانند سیمان انیدریتی و انیدریت‌های پر‌کننده منافذ با کاهش فضای منافذ منجر به افزایش مقاومت الکتریکی می‌شوند.
کلیدواژه‌ها

عنوان مقاله English

A Comparison of the Impact of Different Pore Types on the Electrical Properties of the Dalan and Kangan Carbonate Formations in the Central Part of the Persian Gulf

نویسندگان English

Aliakbar Jahanpanah 1
Vahid Tavakoli 2
1 School of Geology, College of Science, University of Tehran
2 University of Tehran, Tehran, Iran
چکیده English

Porosity and its types are among the most important reservoir characteristics. Formation resistivity is another crucial petrophysical property of reservoirs that allows for the calculation of water saturation and subsequently hydrocarbon saturation. Therefore, investigating the impact of pore type on electrical resistivity will enhance our understanding of the relationship between geological and petrophysical properties and reservoir evaluation, especially in carbonate reservoirs. In this study, cores, plugs, microscopic thin sections and resistivity logs from a well in the Dalan and Kangan carbonate-evaporite formations with a thickness of 342.92 meters were used. A total of 1367 thin sections were prepared from the prepared plugs, and the lithological characteristics, sedimentary textures, pore types and diagenetic processes were determined. Archie's coefficients and water saturation were determined and calculated for each pore type using laboratory and well log data. Then, using water saturation data and laboratory porosity values, the impact and comparison of each identified pore type on electrical resistivity were investigated. The results showed that porosity has a significant impact on electrical resistivity. With an increase in porosity in all pore types, electrical resistivity decreases, but the rate of change and average electrical resistivity in different pores vary. Vuggy porosities, with the highest porosity values, have lower electrical resistivity, while no visible porosities (microporosity), with the lowest porosity values, have a higher average electrical resistivity compared to other identified porosities. In addition, water saturation also plays a significant role in electrical resistivity, and with a decrease in water saturation in all studied porosities, electrical resistivity increases. Diagenetic processes that increase porosity, such as dissolution in moldic porosities and dolomitization in intercrystalline porosities, lead to a decrease in electrical resistivity, and processes that reduce porosity, such as anhydrite cementation and pore-filling anhydrites by reducing pore space, lead to an increase in electrical resistivity.

کلیدواژه‌ها English

Porosity
Pore type
Electrical resistivity
Water saturation
Diagenetic processes
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