Shale type division and logging identification in the Member 1 of Luzhai Formation,Lower Carboniferous,Guizhong Depression
The shale gas of Luzhai Formation in Liucheng North block of Guizhong Depression has made a breakthrough and is expected to become a replacement field for marine shale gas outside Sichuan Basin.However,it is difficult to identify shale type and evaluate reservoir due to the formation heterogene-ity and frequent transverse and horizontal phase transformation.In this paper,a shale type division scheme based on"mineral composition+TOC content"is established.Logging identification and prediction of shale composition and TOC content are realized by using elite-mineral conversion optimization equation and BP neural network model,respectively.The shale layers are identified and characterized by two methods:im-age log dynamic slice and button electrode apparent conductivity image.By elaborating the stratification de-gree and gas bearing characteristics of different lithofacies types,the favorable shale types and distribution characteristics in the study area are described.The results show that five typical shale types are developed in the Member 1 of Luzhai Formation.Controlled by sedimentary palaeoenvironment,the shale distribution in the study area shows strong vertical heterogeneity.The Member 1 of Luzhai Formation is located in the lower slope sedimentary environment as a whole,and the sedimentary water in the vertical layer(①-⑦)gradually becomes shallower,the content of gray matter decreases while the supply of terrigenous debris increases,and the total organic carbon content also gradually decreases.The shale type gradually changes from organic-rich siliceous mixed shale and organic-rich clayey mixed shale to organic-containing siliceous mixed shale.The shale assemblage types of organic-rich siliceous mixed shale and organic-rich clayey mixed shale in small layer ③ has high organic matter abundance,better laminae combination type and de-velopment degree,and higher overall gas content and brittleness,which are favorable shale types in the study area.
万方数据
维普
