Lacustrine Turbidite Classification Feature Researth And Geological Modeling

Lacustrine turbidites are most developed in deep lake and semi-deep lake environment, which have good caprock conditions, and usually form lithologic reservoirs with high reserves. Lacustrine turbidites are the main exploration targets of old oilfield in the eastern part of our country. However, the sand body of turbidite is characterized with small scale, big variety and severe heterogeneity, so the rolling development is difficult. Therefore, it is essential to study the characteristics of different turbidites according to different genetic classification, anatomise the architecture elements of sand body deeply, and set up the corresponding modeling methods. All these study can provide basis for the searching of turbidite reservoir and improving the recovery efficiency of oil and gas.The formation conditions, sedimentary environment and oil-gas enrichment regularity of lake turbidite were analyzed. Lacustrine basin was divided into rifted basin, depression basin, foreland basin and graben basin on the basis of genesis and structure. According to the difference of sedimentary areas, different causes and types of lacustrine basin, lacustrine turbidites could be divided into 6 types: steep-slope turbidite, gentle-slope turbidite, fault-terrace turbidite, fault-trough turbidite, sublacustrine fan and storm turbidite. Based on the studying the geological of Qikou Oilfield, Gaosheng Oilfield and Suizhong Oilfield of Bohai Bay Basin and Yingtai Oilfield of Songliao Basin, steep-slope turbidite, gentle-slope turbidite, fault-terrace turbidite and fault-trough turbidite were studied in detail from the following aspects: depositional background, sedimentary mechanism, lithology, sedimentary structure, logging facies and seismic facies. The sedimentary microfacies of these turbidites were divided, and the features of the microfacies were analyzed, such as lithologic association, sedimentary sequence and sandbody distributing characteristics. The turbidite depositional model and evolution law were established, and the oil-gas control effect of lake turbidite was explained according to the source-reservoir-cap combination condition. The sand body architecture element of lake turbidite was carried thorough the whole research.By analyzing the turbidite sand body geometry parameters of Suizhong Oilfield, Yingtai Oilfield, Qikou Oilfield and Gaosheng Oilfield, the correlation relationship between length, width, area and the maximum thickness of steep slope turbidite and fault terrace turbidite were set up. The statistical results showed that the length-width ratio of sand body could be ranked in descending order as: fault trough type, steep slope type, gentle slope type and fault terrace type. On the basis of field data, the corresponding geological modeling methods were adopt according to different turbidite types. The 3D geological models of steep slope turbidite, gentle slope turbidite, fault terrace turbidite and fault trough turbidite were set up, which could reflect the spatial distribution characteristics of turbidite facies and porosity-permeability-saturation properties more objectively and truly, and provide sufficient scientific basis for the further development of lake basin turbidite reservoir.