地质科技通报 (May 2022)
Re-understanding on hydrocarbon accumulation of the Hetaoyuan Formation in Xiaermen area of the Biyang Depression
Abstract
The Xiermen area is located in the east of Biyang Depression, and the Xiermen Oilfield has been discovered in this area. The upper part of He-3 Member to the lower part of He-2 Member are completely oil reservoirs, while the upper part of He-2 Member is a reservoir with gas cap, and He-1 Member and Liaozhuang Formation are pure gas reservoirs. After more than 40 years of exploration and development, it is increasingly difficult to find new oil and gas reservoirs in the Xiermen area, and oil and gas exploration has reached a bottleneck stage. In order to further expand the exploration scale and obtain new discoveries, it is necessary to re-understand hydrocarbon accumulation mechanism in this area, providing insights for the next exploration direction. Based on source rock characterization, oil to source correlation, natural gas composition and reservoir profile analysis, combined with the latest exploration reservoir data, our results suggest that the He-2 Member has wide distribution of mudstones, and is characterized by low maturity stage, indicative of good hydrocarbon generation potential. The relationship between hydrocarbon from the Xiaermen area and source rocks in the deep depression is clear, indicating that hydrocarbon is laterally migrated; in other words, the He-2 Member low-maturity oil largely comes from the low-maturity source rocks in the deep depression, and crude oils of the upper and lower part of He-3 Member primarily comes from mature source rocks of the upper and lower part of He-3 Member in the deep depression. The He-2 Member natural gas is low maturity oil-associated gas, which is obviously different from the deep-buried condensate gas, excluding the possibility of migration from deep part along faults. There is a large amount of deep oil and gas resources in the Xiaermen area, but the discovered reserves are limited at present, indicating that there is still a great exploration potential in this area. Therefore, summarizing oil and gas accumulation patterns in the Xiaermen area can not only provide guidance for further oil and gas exploration in this area, but also provide example for further exploration of oil-bearing structures in similar fault depression basins in the eastern China.
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