Geological Conditions and Favorable Area Prediction of Shale Gas in Wufeng Formation–Longmaxi Formation of Kuankuo–Fuyan Area, Northern Guizhou

In order to predict the favorable shale gas area of Wufeng Formation – Longmaxi Formation in Kuankuo – Fuyan area, Northern Guizhou Province, on the basis of previous research results, based on data of 26 outcrop profiles and well QSD1, sample analysis and testing, combined with seismic and electromagnetic data, the buried depth of the bottom of Wufeng Formation – Longmaxi Formation, the petrological characteristics and sedimentary facies types of shale, the changes of total organic carbon (TOC), organic matter maturity (Ro) and brittle mineral content are analyzed, and the favorable areas for shale gas are predicted. The buried depth of the bottom of Wufeng Formation – Longmaxi Formation in the study area is mostly 0～1 500 m, and the maximum buried depth is 1 926 m; It is mainly composed of mudstone and silty mudstone, intercalated with thin argillaceous siltstone and occasional marlstone, which is argillaceous deep–water shelf sediments; The thickness of the strata is generally more than 30m, in the northeast is large, and the maximum thickness is more than 90 m, in the southwest is small, and the maximum thickness is less than 50 m; The distribution of TOC is low (<2.0%) in the middle and high (>3.5%) in the northeast and southwest; Ro is between 1.20% and 3.17%, and the average value is more than 2.50%, which is mainly over mature source rock; The content of brittle minerals is more than 50%, which is low (<60%) in the middle and high (>70%) in the northeast and southwest. Based on the above prediction indexes of shale gas favorable areas, the distribution of favorable areas is predicted in three categories. The type I favorable area in the middle of Fuyan Xiaoya syncline is the preferred target area for shale gas exploration in the next step.