مطالعه ژئوشيميايي و كروماتوگرافي گازي بر روي نفت توليدي به روش پيروليز آبي از نمونه‌هاي شيل نفتي حاوي كروژن نوع II در منطقه قالي كوه لرستان ايران

Geochemical and gas chromatography study on oil produced by hydrous pyrolysis from kerogen type II oil shale samples in Ghali kuh Mountain area of Lorestan Iran

در مطالعه حاضر به بررسي ابعاد مختلف ژئوشيميايي و همچنين بلوغ ماده آلي بر روي نمونه­ هاي شيل نفتي قالي كوه به وسيله انجام پيروليز آبي پرداخته مي­شود. قبل از انجام آزمايش به كمك آناليز راك – اول ويژگي­هاي ژئوشيميايي نمونه­ ها مشخص گرديد. نتايج آناليز فوق بيانگر اين موضوع است كه با توجه به دماي بيشينه (Tmax) 418 درجه سانتي گراد براي نمونه ­ها، آن­ها در شرايط نابالغ قرار دارند، ضمن اين كه داراي غناي مناسبي از ماده آلي هستند (TOC=4.33). محيط رسوبي نمونه­ ها نيز با توجه به شاخص­هاي بايوماركري پريستان و فيتان، محيط دريايي تا درياچه­اي با شرايط احيايي است كه حاوي كروژن نوع II نيز هستند. آزمايش پيروليز آبي بر روي نمونه در 6 دماي مختلف صورت پذيرفت. پس از جمع­ آوري نفت و گاز به دست آمده در پايان هر آزمايش، بيشترين ميزان نفت در دماي 330 درجه سانتي­گراد حاصل شد كه مقدار آن 739 ميلي گرم به ازاي 50 گرم نمونه است. نفت توليدي نيز به لحاظ داشتن درصد وزني سولفور و رزين و آسفالتين پايين داراي كيفيت مناسبي است. از لحاظ ايزوتوپ C13 نفت توليدي نيز مقدار آن معادل با دوره سني سازند سرگلو يعني دوره ژوراسيك است. در كل نتايج مطالعه انجام شده نشان مي­ دهد نمونه ­هاي شيل نفتي قالي كوه از لحاظ توان و ميزان توليد هيدروكربن در وضعيت مناسبي قرار دارند، ضمن اين كه مواردي همچون صرفه اقتصادي، ميزان بهره­ وري و ... نيز مورد توجه است كه در مطالعه حاضر به آن پرداخته مي ­شود.

Introduction The first discovery studies on oil shale in the Zagros Basin are in the Qali Kuh region in Lorestan province. The results of their studies showed that Sarglu Formation in Qali Kuh region has the characteristics of oil shale. There are different methods for evaluating rocks in terms of hydrocarbon generation potential. One of the best methods is to use hydrous pyrolysis. This method can determine the production capacity of oil shales by simulating near-reality conditions. Materials and Methods In this study, the hydrocarbon generation potential of Sarglu Formation has been studied using hydrous pyrolysis method. Therefore, for this study, hydrous pyrolysis cell was performed according to the desired specifications. Also, gas chromatography and carbon isotope analysis were performed to complete the studies on the samples. Discussion Hydrous pyrolysis test for oil shale samples of Qali Kuh region is performed at six temperature points of 330, 310, 290, 270, 250 and 350 ° C for 72 hours. Most hydrocarbon generation in this experiment occurs at 330 ° C. At 330 ° C, the percentage of gaseous hydrocarbons and non-hydrocarbon gases (CO2, N2, H2) is set as a bar graph in Figure 1. Fig. 1. percentage of the frequency of different hydrocarbon and non-hydrocarbon compounds in the gaseous product of aqueous pyrolysis at 330 ° C The rock-eval study on the sample of oil shale studied shows that the type of organic matter in the sample of Type II kerogen (Figure 2). Fig. 2. Diagram of hydrogen index versus total organic carbon to determine the type of organic matter In Figure 3, the Pri / n-C17 diagram is plotted in terms of Phy / n-C18. The above data is shown as a blue dot in Figure 3, which shows that the organic matter of samples is mainly of type II kerogen and was deposited in the marine sedimentary environment with reducing conditions. Fig. 3. Graphs of ratios of paristan and phytan biomarkers to normal alkanes and sediment environment indices and kerogen types Conclusion This study showed that the highest oil generation occurs at a temperature of 330 ° C, which is equal to 739 mg of oil per 50 g of sample. According to a study conducted in this region, 15.72 liters of oil is generated per ton of oil shale. In fact, the above study clarifies that with the help of laboratory methods such as hydrous pyrolysis, it is possible to evaluate the production of hydrocarbon compounds such as oil from oil shale samples on a very small scale. This facilitates calculating and accurate estimating of oil production on a large scale.