Forming Condition And Distribution Prediction Of Shale Gas Of Longtan Formation In Northwest Guizhou

The study area is located at northwestern Guizhou province with the high terrainin northeast and low terrain in southwest. Affected by long-term tectonic movements,the study area presents complex structural features with abundance of folds and faults.Longtan formation is mainly distributed at the central and south area of the study areawhich is composed of the marine-terrigenous facies, such as sandstone, siltstone, blackshale and so on.Through the study of previous results such as regional geology, sedimentarysequences and facies, and the experiment tests such geochemistry, physical propertyand gas content, the paper drawn conclusions that the deposition center of Longtanformation is along the Dafang to Xifeng county with the largest thickness of30to40meters; Xishui county has the largest burial depth which is dominated by lagoon-delta-swamp-barrier island facies; the type of Longtan organic matter is III type; TOC isbetween1.0%to10%with an average of6.07%;pore types is dominated by inorganicpores which is different with the marine shales because of different depositionalenvironment and geochemical conditions; the average content of clay minerals andquartz is41.4%and47.8%respectively; gas content is between2.5m3/t to10.0m3/twith the highest value of19.1m3/t; potential shale absorption is between1.88m3/t to8.8m3/t with the average value of4.51m3/t which suggests that the absorption potentialis attractive. In conclusion, the paper believes that the most favorable areas of the UpperPermian shale is distributed at the central area of northwestern Guizhou, includingJinsha, Dafang, Qianxi and Nayong county.