| Because of lacking understanding of oil and gas enrichment regularity in Anyue-Hechuan area, leading to the deployment of porosity reservoir for the object wells in the Anyue area were not eligible for gas, while Hechuan region has made good exploration results. For understanding the mechanism of accumulation in this area is not deep enough, It mainly show in the following aspects: Several factors must control two-stage gas enrichment, for example, air source, structure, reservoir, cracks and so on. But differences exist about gas accumulation between Anyue and Hechuan area and obviously differences also exist in the two regions about the history of gas and later adjustment. The difference of degree have hindered the gas reservoir in the region to be objective and scientific evaluation and understanding, and also has brought great difficulties to the further exploration and development.With description of the rock thin sections and the methods of SEM, mercury curve, X diffraction, seismic interpretation, well logging and other methods, we carried out a comparative study of basic geological characteristics in Anyue and Hechuan area.After analysing the test data of the 2th member of Anyue area, we conclude that the reservoir rock type mainly contain lithic feldspar sandstone and part of it come from feldspar lithic sandstone.In contrast, the reservoir rock type of the 2th member of in Hechuan area mainly contain feldspar lithic sandstone and part of it come from lithic feldspar sandstone.The 2th member of in Anyue and Hechuan area both take low-porosity and low permeability reservoir as the principal thing, but porosity and permeability have correlated better in Hechuan area. It thinks that the Ⅲ, Ⅳ class reservoir are mainly intergranular pore and dissolution pore in Anyue area, and the Ⅰ、Ⅱ class reservoir is mainly intergranular pore. Moreover, reservoir of the 2th member of Hechuan area mostly contain Primary intergranular pore and dissolution pore. The 2th member of Anyue area is short of Core crack, and it is not large, we can divide it into tectonic seam and the seam between the layers. There are mainly high Angle fracture and lesser horizontal fractures of the 2th member of Hechuan area, in addition, the cracks are small.It is reasonable to evaluate hydrocarbon source rocks by the abundance of organic matter, organic matter type, maturity of organic matter and so on, to compare gas sources by the characteristics of natural gas and carbon isotope, to do a analysis to determine trap type by the structural feature combined with the real drilling data, to build a synthetic analysis by the characteristics of evolution of source rocks、oil and gas infilling periods and gas migration, and then established the mechanism of reservoir of gas, restored the accumulation process of gas reservoir. The source rock of Anyue and Hechuan Xujia River for hydrocarbon generation showed some similarity. At the early and middle Jurassic hydrocarbon generation began and to early Cretaceous Epoch it reached the fastigium. At the late cretaceous, the source rock generate the condensate oil and condensate gas mostly, and enter into tectonic uplift stage since Cretaceous periodBy studying the geological characteristics and the mechanism of the reservoir, It reveals enrichment regulation of gas in Anyue- Hechuan area in the following several aspects:(1) Delta-front subfacies sediment,large thickness of a single layer of sand body,belong to gas-rich region;(2) gas-rich in fracture developing zone.(3) gas-rich in high quality source-reservoir effective superimposed area.(4) gas is relatively rich in the area of large reservoir thickness and high energy storage. The gas enrichment regularity in the area of HeChuan:(1) the deposition of delta front provides a good foundation for good reservoir which leads to the enrichment of natural gas.(2) Certain thickness of the "highly porous" sandstone reservoir accumulate gas.(3) Crack is an important condition to promote the gas accumulation with high productivity. Anyue- Hechuan areas are identified as favorable exploration targets by gas accumulation rule and control factors. The six favorable areas of the 2th member of Anyue area shall be optimized, and the north area of the Yue 6 well ~ Yue101-67-X2 well is in accordance with the rule of natural gas enrichment and the development of the present stage is low, which can be used as the focus of the exploration area. Hechuan 1 well、the 2th member of Tongnan and other Areas shall be selected to optimize the 2~3 favorable exploration areas, for example, the regions of Hechuan 6 well ~ Hechuan 001-10~ Hechuan 001-8~ Hechuan 001-28 meet the gas enrichment rules, which can be used as the key areas for exploration. |
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