The Reservoir Formation Conditions And The Patterns Of Yan9Oil Reservoir Of Yan’an Formation In Suijing Area Of Shanbei Slope

The Ordos Basin is the second largest sedimentary basin on land in China which preserves abundant oil and gas resource. It is necessary to do particularity research for the sedimentary facies, the reservoir formation conditions and the reservoir model in order to find the prospective exploration targets.Yan9oil reservoir of Yan’an Formation is the researching strata. On the basis of the Sequence Stratigraphy and sedimentology, combined with the drill, logging, cores and other geological materials, we confirmed the boundary of strata, described the characteristics of the early Jurassic strata, reconstructed the pre-Jurassic palaeogeomorphic of studied area, divided palaeogeomorphic into valley, remnant, slope and highland, analyzed the various characteristics of the palaeogeomorphic units.Based on the facies signs, the sedimentary facies in the Yan9oil reservoir was delta plain subfacies which can be divided into distributary channels, inter-channel bays, natural levee and crevasse channel. The distributary channels sand bodies are the main reservoir, whose extension area and thickness is big, the porosity and permeability is good.By the detailed analysis of the main geologic factors, it is demonstrated that the main source rock of Yan9oil reservoir was high quality hydrocarbon came from Chang7oil reservoir of Yanchang Formation; the distributary channels sand bodies had the dominant position to trap oil and gas; incised-valley was good hydrocarbon migration pathway; nose-shaped uplift and differential compaction structural zone were the main pointing areas of oil and gas migration. Reservoir types are structural reservoir and lithologic structural reservoir. There are two reservoir models, valley-distributary channels reservoir model and slope-distributary channels reservoir model.Pre-Jurassic palaeogeomorphic and sedimentary microfacies are primary factors of controlling hydrocarbon distributing and accumulation; structure and source rock are important factors. Distributary channels with good reservoir properties, nose-shaped uplift and the slope mouth areas in the south of studied area where were near the source rock are the main pointing areas of oil and gas accumulation and distributing.