بررسی آزمایشگاهی نقش اجزای سنگ بر ازدیاد برداشت به وسیله سیلاب‌زنی آب کم‌شور در میدان نفتی شادگان

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی شیمی و نفت، دانشگاه صنعتی شریف، تهران، ایران

2 بخش مهندسی نفت، مواد و معدن دانشکده فنی و مهندسی، دانشگاه آزاد تهران مرکز، ایران

چکیده

ساز و کار‌های تزریق آب کم‌شور در مخازن کربناته به دلیل طبیعت پیچیده آن نسبت به مخازن ماسه‌سنگی به خوبی درک نشده است. با استفاده از سنگ آهک و نفت خامِ یکی از چاه‌های میدان نفتی شادگان، آزمایش تزریق مغزه با توالی آب پرشور و کم‌شور انجام شد. آب دریای 10 بار رقیق شده به عنوان آب کم‌شور توانست 5/14% از نفت درجای اولیه را پس از تزریق ثانویه آب دریا بازیافت کند. در نقطه مقابل، تزریق ثالثیه همان آب کم‌شور در سنگ مصنوعی از جنس کلسیت خالص (با خواص پتروفیزیکی مشابه با سنگ واقعی) تنها 4/3% از نفت درجای اولیه را تولید کرد.  نتایج زاویه تماس، ازدیاد برداشت نفت در تزریق آب کم‌شور را به تغییر ترشوندگی سنگ‌ها به سمت آب‌دوستی بیشتر نسبت داد. با این حال، میزان تغییر ترشوندگی در سنگ آهک میدان نفتی شادگان (°42) نسبت به سنگ کلسیتی خالص (°16) به صورت معنی‌داری بیشتر بود. بر اساس نتایجِ پتانسیل زتا، تغییر ترشوندگی توسط آب کم‌شور به منفی‌تر شدن بار الکتریکی میان‌رویه‌های نفت خام/ شورآب و سنگ/ شورآب نسبت داده شد. روند افزایشی pH با کاهش شوری نشان داد جذب بیشتر CO3-2 در شوری پایین عامل کاهش بار الکتریکی سطح کلسیت می‌باشد. میزان بار الکتریکی سنگ آهک میدان نفتی شادگان در ازای کاهش شوری آب تزریقی از آب دریا به آب دریای 10 بار رقیق شده کاهش بیشتری (mV 7/7) نسبت به  سنگ کلسیتی خالص (mV 1/4) تجربه کرد. نتایج طیف‌سنجی فلورسانس پرتوی ایکس این رفتار را به حضور ناخالصی‌هایی همچون سیلیکا، سولفات و فسفات در سنگ آهک میدان نفتی شادگان نسبت داد.
 

کلیدواژه‌ها


عنوان مقاله [English]

Experimental Investigation of the Role of Rock Components in Enhanced Oil Recovery Using Low Salinity Water Flooding in Shadegan Oil Field

نویسندگان [English]

  • Hamed Farhadi 1
  • Mahdi NazariSaram 2
1 Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran
2 Department of Petroleum, Engineering and Technical Faculty, Islamic Azad University Central Tehran Branch, Tehran, Iran
چکیده [English]

Due to the complex nature of carbonate reservoirs, mechanisms behind low salinity water injection (LSWI) in these reservoirs are not well understood compared to sandstone ones. Using a limestone core and crude oil from one of the wells of the Shadegan oil field, a core injection test was performed with a sequence of high salinity-low salinity water. 10-time diluted seawater, as low salinity water, was able to recover 14.5% of initial oil in place (IOIP) following the secondary injection of seawater. In contrast, the tertiary injection of the low salinity bine into artificial pure calcite rock (with petrophysical properties similar to real rock) recovered only 3.4% of IOIP. Using the results of the contact angle test, the improved oil recovery by LSWI is attributed to wettability alteration towards a more water-wet state. However, the amount of wettability alteration in Shadegan oil field limestone (42°) is significantly higher than that of pure calcite rock (16°). Based on the results of zeta potential, the wettability alteration by low salinity water is attributed to the more negative electric charge of the crude oil/brine and rock/brine interfaces. The increasing trend of pH with decreasing the salinity showed that more CO32- adsorption at low salinity reduces the electric charge on the calcite surface. The electric charge of Shadegan oil field limestone, by reducing the salinity of injected water from seawater to 10-time diluted seawater, experienced a greater decrease (7.7 mV) than pure calcite (4.1 mV). XRF results attributed this behaviour to the presence of impurities such as silica, sulphate, and phosphate in the Shadegan oil field limestone.

کلیدواژه‌ها [English]

  • Enhanced Oil Recovery
  • Low salinity water flooding
  • Fluid-Fluid and Rock-Fluid Interactions
  • Zeta Potential
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