| The Carboniferous-Permian in the Huanghua Depression of the Bohai Bay Basin is rich in oil and gas resources and is an important field of oil and gas accumulation in buried hills.Based on the regional tectonic background of the Bohai Bay Basin and the sedimentary characteristics and evolution of the Carboniferous-Permian,the research focus of buried hill hydrocarbon accumulation is to analyze the control effect of buried hill hydrocarbon accumulation conditions,including the rules of hydrocarbon generation in source rocks,the development of high-quality reservoirs and the formation of buried hill traps.This has certain practical significance for increasing oil and gas reserves.This paper takes the Upper Paleozoic buried hill in Huanghua Depression as the research object,based on the field outcrop and well-seismic data,collates and summarizes the previous research results,explores the control effect of tectonic evolution on the hydrocarbon accumulation conditions of the Carboniferous-Permian,and the research results show that :(1)The North China Platform has experienced four stages of evolution: cratonization,stable development,cracking failure and extensional rifting.Under this background,the sedimentary filling of the Carboniferous-Permian is established on a stable carbonate platform.After going through the ?two-phase reconstruction and two-phase construction? of the Mesozoic and Cenozoic,the Carboniferous-Permian finally showed the characteristics of a residual basin.(2)The Taiyuan Formation and Shanxi Formation coal measure strata are the main stratum of the source rocks in buried hills.Tectonic evolution promotes its hydrocarbon generation process into two stages,which correspond to the early and middle Yanshan movement and the Himalayan movement period,respectively.Hydrocarbon generation modes include continuous burial type,early uplift and late burial type,and intermittent burial type.In addition,the threshold of secondary hydrocarbon generation in the study area is greater than the threshold of primary hydrocarbon generation.Wumaying,Wangguantun and Qikou deep concave areas are the most favorable zones for hydrocarbon generation.(3)The storage space of high-quality Carboniferous-Permian reservoirs is mainly composed of secondary pores,supplemented by fractures,and few primary pores.The effective range of structural fractures for reservoir reformation is within 759 m from the main fault.The transformation of the reservoir by dissolution is divided into: organic acid dissolution-atmospheric freshwater leaching composite mode,organic acid dissolution dominant mode,and atmospheric freshwater leaching dominant mode.Among them,the third mode has the widest distribution and the greatest transformation intensity.(4)The types of buried hill traps developed in the study area include: anticline traps,thrust traps,paleomorphological traps and tilt fault block traps.Different types of traps have different formation processes under the control of tectonic evolution.Among them,the traps of tilting fault blocks are the most widely distributed,the anticline traps are mainly distributed in the south,the paleomorphological traps are mainly distributed in the north,and the thrust traps are scattered.The typical buried hill reservoirs are analyzed,and it is found that the buried hill reservoirs in the study area include: Paleozoic oil and gas stored in Paleozoic reservoirs or Cenozoic oil and gas stored in Paleozoic reservoirs.Under the control of structural evolution,buried hill oil and gas reservoirs reflect the reasonable allocation of effective source rocks,high-quality reservoirs,and good traps.Areas such as Wumaying,Wangguantun and northern Qibei-Chenghai areas with good trap conditions,source-reservoir-cap rock assemblages and preservation conditions are conducive to oil and gas accumulation in buried hills.The above analysis has certain guiding significance for buried hill oil and gas exploration. |
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