ارزيابي پتانسيل هيدروكربن‌زايي و تاريخچه تدفين سنگ‌هاي مادر محتمل در ميدان سلمان، شرق خليج فارس

ميدان سلمان، يكي از مهم­ترين ميادين توليدي در بخش شرقي خليج فارس محسوب مي­شود كه در افق­هاي كنگان/دالان داراي گاز و در افق­هاي سورمه، گدوان و داريان داراي نفت است. پژوهش حاضر به بررسي پتانسيل هيدروكربن­زايي سازندهاي گورپي، سروك، كژدمي، داريان، گدوان، فهليان، سورمه و سرچاهان در ميدان سلمان با استفاده از اطلاعات پيروليز راك­اول، انعكاس ويترينايت و نتايج مدل­سازي يك بعدي در يكي از چاه­هاي عميق ميدان، مي­پردازد. بدين منظور 50 نمونه سنگ، بجز سازند سرچاهان، از اعماق مختلف در دو چاه، مورد آناليز و ارزيابي قرار گرفت. نمونه­هاي مربوط به سازندهاي سروك و سورمه به ترتيب پتانسيل هيدروكربن­زايي خوب و متوسط را نشان دادند در حالي كه بقيه نمونه­ها داراي پتانسيل ضعيف بودند. مواد آلي سازند سروك داراي كروژن تيپ II و مواد آلي سازند سورمه داراي كروژن تيپ II/III بودند. بنابر انعكاس ويترينايت حاصل از پتروگرافي و مدلسازي، سازند سروك نابالغ، سازند سورمه در اوايل پنجره نفتي و سازند سرچاهان در پنجره گازي قرار دارند. نسبت تبديل براي سازند سرچاهان، 95 درصد است در حالي كه اين نسبت براي سازندهاي سروك و سورمه صفر مي­باشد.

Introduction The Persian Gulf basin is one of the most prolific and important hydrocarbon provinces in the world. The presence of rich source rocks, fractured carbonate reservoirs, effective cap rocks alongside large anticlines has led to the accumulation of large volumes of oil and gas in this area. This study investigates the hydrocarbon generation potential of probable source rocks in Salman field through using Rock Eval, vitrinite reflection and 1D model results in one of deepest wells. Materials and methods In this study, Rock-Eval 6 and Vitrinite reflection were used to evaluate the hydrocarbon generation potential of source rock samples. Accordingly, 50 and 18 rock samples from Gurpi, Sarvak, Kazhdumi, Dariyan, Gadvan, Fahliyan and Surmeh formations in two wells of Salman were analyzed, respectively. Moreover, one-dimensional modeling of burial history was performed by using Petromed software (2011-Schlumberger) on well B of Salman field. Results and discussion The TOC of the samples is between 0.16 and 2.83%, of which about 90% have a value less than one. Petroleum potential index (S1+S2) varies from 0.43 to 17.5 mg HC/gr Rock. The highest TOC and petroleum potential index values are related to Sarvak samples. Surmeh samples indicate fair petroleum generation potential while the rest of the samples indicate poor petroleum generation potential. Based on HI, Sarvak and Surmeh samples have kerogen type II and II/III respectively. Vitrinite reflectance values range from 0.3 to 0.55, indicating that the samples are in the immature to early mature stages. One-dimensional modeling was performed to determine the burial and thermal history of the Sarchahan, Surmeh and Sarvak source rocks and the time of hydrocarbon generation at well B. The temperature history of the layers in the sedimentary basin is estimated by model and calibrated by vitrinite reflections. According to estimated vitrinte reflection (Sweeney and Burnham model), Sarvak Formation is immature and Surmeh Formation is early mature. The Sarchahan Formation is currently in gas window. This formation has entered the peak of the oil window since 157 million years ago and entered the gas window since 75 million years ago. Conclusions Geochemical assessment of different formations in Salman field confirmed that Sarvak, Surmeh and Sarchahan formations are the most important source rocks in the eastern part of the Persian Gulf. Sarchahan source rock is in the gas window and has produced 95% of its potential so far. Organic matters of Sarvak and Surmeh formations have kerogen type II and II/III, respectively. Sarvak Formation is immature and Surmeh Formation is in the early oil window. Although Sarvak Formation is immature in Salman field, it could generate high amounts of hydrocarbon by increasing depth in the eastern parts of Salman oil fields.