بررسی عوامل کلیدی مؤثر بر دقت محاسبات اشباع آب در مخازن کربناته: سازندهای کنگان و دالان، غرب خلیج فارس

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده زمین‌شناسی، دانشکدگان علوم، دانشگاه تهران، تهران، ایران

چکیده

ارزیابی خصوصیات مخازن کربناته باتوجه‌به ناهمگنی بسیار زیاد این مخازن، همواره با دشواری‌ها و عدم‌قطعیت‌های زیادی همراه است. اشباع آب یکی از پارامترهای بسیار مهم در ارزیابی این مخازن به شمار می‌آید. علاوه بر این، تأثیر اشباع آب بر مکانیک سنگ به‌عنوان یک پدیده‌ی مهم در مهندسی ژئوتکنیک شناخته می‌شود. رایج‌ترین رابطه برای اشباع آب، معادله‌ی آرچی است. دقت اشباع آب محاسبه شده از طریق معادله‌ی آرچی به‌دقت پارامتر‌های آن از جمله ضریب سیمانی‌شدن، ضریب پیچاپیچی و ضریب اشباع بستگی دارد. ناهمگنی مخازن کربناته، به طور قابل‌توجهی بر ضرایب معادله‌ی آرچی و در نتیجه محاسبات اشباع آب تأثیر می‌گذارد. در این مطالعه، از ۱۵۷ داده‌ی اشباع آب دین استارک، ۵۷ داده‌ی فاکتور مقاومت سازند، ۲۰ داده‌ی شاخص مقاومت سازند، ۱۳۶۸ مقطع نازک و ۱۱۱۴ داده‌های تخلخل و نفوذپذیری تهیه شده از یک چاه اکتشافی در غرب خلیج‌فارس استفاده شده است. به‌منظور مدیریت ناهمگنی، از روش‌های مختلفی از جمله روش راندمان الکتریکی، نشانگر زون جریان و وینلند استفاده شد. پس از دسته‌بندی سنگ‌ها با پارامترهای الکتریکی و پتروفیزیکی مشابه، پارامترهای آرچی در دسته‌های مختلف محاسبه شدند. سپس اشباع آب با استفاده از رابطه‌ی آرچی در هریک از دسته‌های تعیین شده، محاسبه و با اشباع آب دین استارک مقایسه شد. علاوه بر این، پارامترهای تأثیرگذار بر دقت اشباع آب، موردبحث و برسی قرار گرفت. نتایج، اهمیت برسی ویژگی‌های رفتار الکتریکی و شعاع گلوگاه‌های منفذی به‌عنوان عوامل کلیدی مؤثر بر دقت محاسبات اشباع آب را نشان دادند. بر اساس یافته‌ها، استفاده از پارامترهای ثابت آرچی منجر به محاسبه اشباع آب، بیش از اندازه‌ی واقعی و در نتیجه، برآورد کمتر از میزان واقعی هیدروکربور در مخازن می‌شود. یافته‌ها نشان داد که مدیریت ناهمگنی مخزن به روش راندمان الکتریکی، تأثیر قابل‌توجهی بر افزایش دقت اشباع آب پیش‌بینی‌شده در مقایسه با دیگر روش‌ها دارد. در مقابل، روش وینلند بیشترین عدم‌قطعیت را در پیش‌بینی اشباع آب دارد.

کلیدواژه‌ها

عنوان مقاله [English]

Examining Key Factors Influencing the Accuracy of Water Saturation Calculations in Carbonate Reservoirs: A Case Study of Kangan and Dalan Formations in the Western Persian Gulf

نویسندگان [English]

  • Sajjad Omrani
  • Vahid Tavakoli
School of Geology, College of Science, University of Tehran, Tehran, Iran
چکیده [English]

Evaluating the characteristics of carbonate reservoirs, given their significant heterogeneity, is always accompanied by challenges and high uncertainties. Water saturation is a crucial parameter in assessing these reservoirs, and the Archie equation is commonly used for water saturation estimation. Moreover, the effect of water saturation on the mechanical behavior of rock is recognized as an important phenomenon in geotechnical engineering. The accuracy of water saturation calculated through the Archie equation depends on the precision of its parameters, including cementation exponent, saturation exponent, and tortuosity exponent. The heterogeneity of carbonate reservoirs significantly affects the Archie equation coefficients and, consequently, water saturation calculations. In this study, various methods, including the electrical efficiency, current zone indicator, and Winland method, were employed to manage reservoir heterogeneity. Subsequently, Archie parameters were calculated for each category, and water saturation was determined and compared with Dean-Stark water saturation. Furthermore, the influential parameters on the accuracy of water saturation were discussed and examined. To achieve the study objectives, 157 Dean-Stark water saturation data, 57 core plug samples for formation resistivity factor (FRF) determination, 20 core plug samples for measuring formation resistivity index (FRI), 1114 porosity and permeability measurements from core plug samples and 1368 thin sections were utilized from an exploration well in the western Gulf of Persian. Our findings highlight the significance of exploring electrical behavior characteristics and pore throat radii as crucial elements influencing the precision of water saturation calculations. As per the results, employing constant Archie parameters leads to an overestimation of water saturation and, consequently, an underestimation of hydrocarbon reserves. Our analysis illustrates that effectively managing reservoir heterogeneity through the electrical efficiency method significantly improves the accuracy of predicted water saturation compared to other approaches. Conversely, the Winland method exhibits the highest uncertainty in predicting water saturation.

کلیدواژه‌ها [English]

  • Rock type
  • electrical efficiency
  • Archie parameters
  • heterogeneity management
  • current zone indicator
  • electrical conductivity

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نشریه علمی ژئومکانیک نفت
دوره 7، شماره 1
فروردین 1403
صفحه 12-24

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