Analysis Of Accumulation Characteristics And Main Controlling Factors Of Buried Hill Oil Reservoirs In Shulu Sag, Jizhong Depression

Shulu sag is located in the southern part of Jizhong depression in Bohai Bay Basin,and is a north-eastward single-fault kei-shaped sag formed in the late Yanshan-Paleogene tectonic movement.The oil and gas resources in the region are abundant,and many sets of oil-bearing systems,such as Guantao Group,Paleogene dongying Group,Shahe Street Group and Basement Qianshan,have been found.Among them,the proven reserves of Qianshan Reservoir account for only 18.3%of the proven reserves in the whole region,and the exploration degree is low.In this area,the open strata of buried Hill are changed greatly,the structure is complex,the understanding of oil and gas accumulation law is unclear,and the study of reservoir formation characteristics and main control factors of reservoir formation needs to be strengthened to provide favorable support for future exploration and development work.Guided by the Theory of petroleum geology,combined with earthquake,logging,logging,core,oil test and means of production,this study uses modern analytical and detection technology to carry out the analysis of reservoir formation characteristics and main control factors of Qianshan in Shulu sag,Through the analysis of organic matter content,type and fluid inclusions,the oil source and reservoir formation period of Qianshan Reservoir are analyzed,According to the location of reservoir,reservoir scale,test mining and crude oil properties,the reservoir formation characteristics of Qianshan reservoirs are summarized,the types of Qianshan reservoirs are analyzed,the effects of oil production,migration and trap conditions on reservoir formation are studied,and the reservoir formation pattern of Qianshan reservoirs in Shulu sag is always ended.The results show that the hydrocarbon source rocks in Qianshan Reservoir in the Shulu sag are in good condition,and two sets of hydrocarbon source rocks are developed,which correspond to two sets of strata,sand first bottom and third lower,respectively,among which the organic matter content of sand third source rock is high,most of which has entered the mature stage,is the main hydrocarbon supply source.The permeable rock formations with stable development and good connectivity of the two-stage fault,the Qianshan at the top of the slope area and the Shahe Street group in the Near East and east are the main channels for oil and gas migration.Qianshan Ordovician,Jixian County Wumi Mountain Group is a good carbonate reservoir,its overlying Paleogene,Neogene mudstone,Carboniferous-Permian mudstone and Qianshan Insider shale for high-quality cover layer,played a role in blocking oil and gas migration.The main controlling factors of reservoir formation are as follows:first,the mature source rocks developed in the lower part of the depression and slope control the oil and gas filling degree and the crude oil quality of the buried hill reservoir;Secondly,fault migration system and unconformity surface migration system control the oil and gas supply channel of buried hill reservoir,permeability lithologic migration system is the transitional stage of these two migration systems,third,trap conditions control the accumulation of buried hill reservoir.Four types of reservoir formation models of buried hill reservoir in Shulu sag are summarized:buried hill reservoir with fault back slope,buried hill reservoir with fault block,formation reservoir with inside shielding buried hill and residual hill buried hill reservoir.It is pointed out that the enrichment area of buried hill reservoir with fault back slope is around the paleouplift in the depression area.The north and south end of the slope area are the enrichment areas of buried hill reservoir of fault block and hidden buried hill reservoir,and the upwelling zone of Ningjin uplift is the enrichment area of residual hill buried hill reservoir.