Geological characteristics of shale gas of the Wufeng Fm-Longmaxi Fm in DD1 well in Northeast Yunnan and their exploration significances

Shale gas exploration of the Wufeng Fm-Longmaxi Fm outside Sichuan Basin is much more difficult than that within Sichuan Basin. In this paper, taking the DD1 well in Yiliang County, northeastern Yunnan as an example, we discussed geological characteristics of shale gas of the Wufeng Fm-Longmaxi Fm in DD1 well in Northeast Yunnan and their exploration significances. The geological conditions of shale gas of DD1 well are evaluated by drilling data, logging, core analysis and testing. The results show, comparing to wells in Sichuan Basin, the organic shale of the Wufeng Fm-Longmaxi Fm in DD1 well is with a thinner thickness, a lower organic matter abundance, a higher thermal evolution level, and poor gas-bearing and N₂ bearing leavels. The main evaluation indicators in DD1 well are obviously different from those of high-yield shale gas wells such as JY1 Well and N203 Well in Sichuan Basin. By comparing main evaluation parameters of shale gas of wells in Sichuan Basin to those out Sichuan Basin, we think there are three reasons which led to the failure of shale gas exploration in DD1 Well. First, the DD1 Well is close to the Central Guizhou paleo-uplift, and the Wufeng Fm-Longmaxi Fm in DD1 Well is shallow tidal flat deposit, lacking the material basis of black organic shale. Second, The high Ro of the Wufeng Fm- Longmaxi Fm shale in DD1 Well resulted in poor porosity. Third, the burial depth of the Wufeng Fm-Longmaxi Fm in DD1 Well is shallow, and multiple scale fractures are developed, and shale gas escaped seriously. DD1 Well has a very poor shale gas preservation condition. The failure of shale gas exploration in DD1 well provides a reference for shale gas exploration outside Sichuan Basin.