Reservior Forming Conditions Of 1st Member Of Liushagang Formation In Fushan Sag

The 1st member of Liushagangformation(ELs1) is the main producing oil stratum in Fushan sag. With the development of oil and gas exploration, the oil deposit of ELs1 seems very complicated. The situation of oil and gas resources of ELs1 has not been identifiedyet. Thenfurther study of reservoiring conditions has great significance to resource potential evaluation and guidance of the formation of oil and gas exploration.Thereforce, this paper is to attempt to analyze the reservoir condition of ELs1 and forecast favorable areas.Based on seismic, logging, well logging and gravity-magnetic data, guided by sedimentology, sequence stratigraphy and petroleum geology, this study is to research tectonic structure, fault distribution and tectonic evolution characteristics of Fushan sag by using tectonic evolution analysis technology, palaeotopography recovering technology, fine structure interpretation, seismic attribute extraction analysis, joint well seismic reservoir prediction technology, formation lithologic trap identification and description, reservoir analysis and evaluation.Specifically, distribution range of strata, paleogeomorphy, sedimentary environment, sedimentary model and the changing rule of the different sedimentary facies belt, hydrocarbon accumulation conditions, main controlling factors and models of petroleum accumulation are studied to forecast favorable oil and gas accumulation zones and guide the deployment of oil and gas exploration.Research results show that bi-layered fracture system is developed in Fushan sag which resulted in west-east differentiation and north-south dissimilitude. Two sub-sags means the deposition centers moved northeastward gradually. Dark mudstone of 2ed member of Liushagangformation(ELs2) with large thickness and high evolution of maturity is the main hydrocarbon source rocks. There developed four main sources and seven sedimentary systems. The braided river delta sedimentary system in the south and short axial fan deltasedimentary system in both the east and west sides are widely distributed. Sandstone is the main reservoir. At present, most of oil and gas is found in both sides of the deep fault which came from ELs2 mainly controlled by faults providing the pathway for the oil-gas migration. Fractures and lithology control the distribution of oil and gas. The accumulation of oil and gas has 3 different stages and matches well with reservoir forming condition. Structural reservoir, updip pinch out reservoir, structural-lithologic reservoir, sand lenses and low porosity-permeability are the main five types of reservoir of ELs1.Chaoyang, Huachang and Yong’an areas are favorable zones for further oil and gas exploration after the comprehensive evaluation of ELs1.