The Key Factors Of Gas In Longmaxi Formation Of Silurian In Guizhou Qianbei Area

In this study,the distributary characteristics and geological setting of organic-rich shales in the Zhengan area of the Guizhou Province have been analyzed.The basic parameters such as the gas content of the shales have been tested.Then the shale gas resource quantity has been calculated.Due to the limited data of this study area,the Anye1 well as the first well in the Zhenan area has significant meaning for the future exploration of shale gas resource.This study is concentrated on the test of shale gas content in the interval between the Longmaxi Formation of the Lower Silurian and the Wufeng Formation of the Upper Ordovician,and then analyze the influencing factors.Through carefully observation of the cores and lithic fragments,we concluded that the main rock type of this interval is black-blackish carbonaceous shale.The target depth is between 2303m and 2331.6m with the thickness of 28.6m.The core is between 2317.6m and 2331.6m with the thickness of 14.4m.The main rock type is black carbonaceous shale.This interval has high total hydrocarbon and TOC.The TOC can up to 4.730%.There are several ways to test the gas content,including the desorption method,the isotherm-adsorption method,the theoretical calculation method,and so on.In this study we chose the desorption method and the well logging interpretation method.First we calculated the lost gas content through the desorption method and got the total gas content.Then we compared this result with the well logging interpretation result.The well logging interpretation method is a better way to calculate gas content,but it needs to be calibrated by the desorption results.In this study,the desorption method is a more reliable way.The gas content of the study interval is between 2.626and 6.488 m~3/t,and most of the test results are more than 3m~3/t.The lower part of the Longmaxi Formation and the upper part of the Wufeng Formation have higher gas content.The total hydrocarbon and the gas content have positive correlation.The strata pressure and the Ro also have important impacts on gas content.In the lost gas content calculation procedure,the results of linear and polynomial regression methods are more reasonable as calculative parameters.