| Shulu Depression is located in the south of North China Hebei Depression east-cracked, west-super, single dustpaned depression. There are two sections of hydrocarbon source rocks in the lower part of Shahejie Formation and the lower three members of Shahejie Formation. Among them, the lower three members of the Sha formation is dark grey mudstone, with high carbon abundance, good type and moderate maturity, it is considered to be a potential layer for shale oil / tight oil exploration. It has established the "marl self-storage" source-reservoir integrated reservoir model and conglomerate of source rock and reservoir accumulation model were generated.However, the oil source problem has not yet been unified. In this study, a detailed oil source correlation study of oil and gas shows and potential source rocks revealed by current drilling is carried out by means of molecular isotope geochemistry. The results show that there are three kinds of crude oil in the Shulu depression. Firstly, based on the oil conglomerate of the SQ1 sequence in the bottom of the Shutan3 well, the crude oil derived from the gypsum salt phase source rocks; secondly, the source rocks of SQ2 sequence are authigenic and self-storing crude oils, the distribution of these crude oils may vary with maturity and change their geochemical properties along the plane of the sag; the third crude oil,with a beam of exploratory well Shutan3 in first and second core wells widely fractured oil and obvious, this kind of crude oil mainly from the deep SQ4 and SQ5 sequence of hydrocarbon source rocks. The crude oil in the exploratory well test has mixed source characteristics,and the carbon isotopic composition of n-alkanes reflects its homology. The main source is freshwater lacustrine source rock, and the low salinity brine source rock is supplemented. Biomarkers and differences of n-alkanes hydrogen isotopic composition of crude oil accumulation process has revealed, "the nearest independent reservoir,adjacent source rocks for hydrocarbon characteristics",thermal evolution degree between the nature of the crude oil reservoir by mainly for their source rocks from different foci. According to the vitrinite reflectance measured results, combined with the organic molecular geochemical characteristics, exploration wells reveal sand three 3 beam under sub paragraph SQ2 below has entered the peak early,SQ3 entered the early stage of oil generation,while SQ4 and SQ5 in immature low mature stage. At present, the main source of crude oil comes from SQ2 sedimentary source rock, accompanied by a set of oil source contribution of gypsum salt facies source rock.According to hydrocarbon fluid properties, can be divided into three independent fluid systems in the vertical direction, the fluid system I and fluid system II by SQ2 and SQ3 between the conglomerate layer as a spacer layer,fluid system between II and III spacer fluid system may also belong to a gravel stratum. The hydrocarbon generation processes of the three fluid systems are different. The enrichment of I hydrocarbon gas in the fluid system is mainly concentrated in the SQ3 top to the bottom of the SQ4,which belongs to the typical vertical migration and accumulation. The fluid system II is a typical self-generating and self-storing reservoir. At the same time,the generated oil and gas does not break through the gravel layer between SQ2 and SQ3, and is well separated from the fluid system ?. ? system of migration hydrocarbon accumulation in fluid system. On this basis,a new model of tight oil shale oil accumulation is proposed in order to guide the next tight hydrocarbon / shale oil exploration in the sag. |
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