Research on Brittleness of Shale in Longmaxi Formation, the Southeastern Chongqing Area

摘要

This article studies Longmaxi exposures in southeast of Chongqing, and carries on experiments to analyze the feasibility of the fracturing from the aspect of brittleness. The results show that the shale is well bedded, tight, and has low porosity and low permeability in this area. And it needs to be reconstructed. The analysis of the mineral components shows that Longmaxi shale has a high content of brittle minerals, such as quartz and carbonate, and the content of these brittle minerals ranges from 49% to 65%, with an average of 57%. While the clay mineral content is low, and there is no kaolinite or montmorillonite which contains serious hydration expansion. On the basis of it. the shale brittleness coefficient calculated by the mineral composition and dynamic elastic parameters ranges from 49% to 77% and the average brittleness coefficient is higher than 57%, which shows the formation is brittle. Comparison with the successful exploitation of the North American shale reservoir, Longmaxi shale in southeast of Chongqing is fit for fracturing operations. According to the North American shale fracturing practical experience, we suggest that the rock brittleness should be taken into consideration in the fracturing design process, and the fracturing fluid should be with large volume of fluid, low proppant content and less proppant consuming.