Shiyou shiyan dizhi (Nov 2022)
Source and migration direction of hydrocarbon in Lower Paleozoic in Gubei buried hill, Jiyang Depression, Bohai Bay Basin
Abstract
In order to clarify the characteristics of oil and gas migration and accumulation in the Lower Paleozoic of the Gubei buried hill and guide the direction of further oil and gas exploration, the hydrocarbon generation, transportation, migration and accumulation were systematically studied based on the data of drilling, seismic and testing. The oil and gas in the Lower Paleozoic of the study area were mainly sourced from the third member of the Shahejie Formation in the Bonan Sag. Faults and the weathering crust of the Lower Paleozoic provided channels for oil and gas migration. The active period of NE trending faults and EW trending basin-dipping faults is consistent with the hydrocarbon generation period of the Bonan Sag, and is one of the important channels for oil and gas migration. The weathering crust on the top of the buried hills in the Lower Paleozoic has big thickness, good physical properties and strong seepage ability, which can be regarded as a good transport layer for long-distance lateral migration of oil and gas. Crude oil mainly migrated from west to east and north to south. The western buried hill and the Bonan subsag are connected by the Guxi No. 1 fault, and the oil and gas generated in the Bonan subsag can be directly migrated to the western buried hills. For the central and eastern buried hills, oil and gas first migrated eastward along the Chengdong and Gubei faults to the lower part of the buried hill, and then migrated and accumulated to the higher part along the Lower Paleozoic weathering crust. Meanwhile, the oil and gas in the central buried hill migrated into the eastern buried hill along the EW trending basin-dipping faults F1 or F2. The central part of the western buried hill, the rising wall of the Chengdong fault in the north of the central buried hill and the whole eastern buried hill area are key targets for further exploration in the study area.
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