Heterogeneity Of Hydrocarbon Distribution In E₂d₁ In Yongan District Of Jiangsu Oil Field

The first member of Dainan formation in Yongan District has considerable oil and gas reserves. It is in the progressive exploration and development stage, and hydrocarbon distribution has heterogeneity. Guided by the theories of modern hydrocarbon accumulation and distribution, this paper summarized the heterogeneity characteristics of hydrocarbon macroscopic distribution and distribution in key fault-blocks in E₂d₁ in Yongan District. Furthermore, it deeply analyzed the main controlling factors of hydrocarbon heterogeneous distribution on different levels, and subsequently made a quantitative evaluation of the hydrocarbon accumulation differences. Finally, the favorable rolling target area was proposed.The heterogeneity of hydrocarbon distribution in E₂d₁ in Yongan District shows as follows: In the plane, the oil reserves, oil domain, and the oil-bearing formation have diversities; the oil and gas mainly accumulate in the fault-blocks dropping to the south which are located in downthrow block of Hanliu Fault. In the vertical, there are many oil-bearing series. There exists differences reflecting in the amount of hydrocarbon reservoir, the ratio of oil and gas containing, and the thickness of hydrocarbon zone. Hydrocarbon mainly enriches in Ⅱ、Ⅲ sand groups, and it increases from bottom to top within a sand group. Hydrocarbon distribution characteristics and degree have diversities in different layer within a fault block. The shape of hydrocarbon distribution in deep zone block, middle zone block and shallow zone block shows ?convex?, ?concave?, ?convex? in the section plane. In general, the physical properties of crude oil have the characteristics of low-density, low-viscosity, middle-freezing point. Along the migration, density and viscosity of the oil are gradually increasing, showing the differential accumulation of hydrocarbon phenomenon. Hydrocarbon reservoir types are various, and the main types are the fault block reservoirs, fault-nose reservoirs and fault-lithologic reservoirs. The main reservoir type, quantity and scale are different in different fault blocks.Hydrocarbon source condition and the distance between traps and hydrocarbon source, reservoir condition, the seal ability, the interaction of multiple elements are main controlling factors of the hydrocarbon heterogeneous distribution in this area. The distribution of mature hydrocarbon source and the distance between the hydrocarbon source and traps are the factor contributing to the hydrocarbon heterogeneous distribution among different fault blocks in the plane and different sand groups in the vertical. The distribution characteristics of reservoir, and the physical property of the reservoir are the key factor making hydrocarbon heterogeneous distribution in different series of strata. The variety of thickness of barrier, the control of the faults contribute to the complexity of hydrocarbon distribution.According to the main controlling factors study the hydrocarbon heterogeneous distribution, the evaluation model of heterogeneous distribution in study area is established. Multi-level fuzzy comprehensive evaluation methods are used to quantitatively evaluate the hydrocarbon accumulation differences in the fault blocks and different layers. The results of comprehensive evaluation divide the subjects into four categories. Quantitative characterization and evaluation of hydrocarbon heterogeneous distribution features is achieved, and a favorable target area is forecasted.