Shale Fracture Characteristics and its Main Controlling Factors in the Southeast of Chongqing

Zeng, Weite; Zhang, Jinchuan; Ding, Wenlong

Gas production relies on hydraulic fracture stimulation. Natural opening-mode fractures reactivate during stimulation and enhance efficiency by widening the treatment zone.We characterized natural fractures in Longmaxi Shale from Yuye-1 well core and Niutitang shale from Yuke-1 well core in terms of size and sealing properties.We researched regional geological structural evolution and analyzed shale geochemistry test data, include TOC and mineralogy,by statistical method.The controlling factors of shale natural fractures had been confirmed and which had been analyzed qualitative or semi-quantitative . The results show that fractures are abundant, in both Longmaxi Shale from Yuye-1 well core and Niutitang shale from Yuke-1 well core ,due to the multiphase Strong tectonic movement in the southeast of Chongqing.For Yuke-1 well, shale mineralogy is high degree of discrete with strong heterogeneity ,therefore,the development and distribution of fractures are controlled by quartz and dolomite content in shale,moreover, the quartz content shows positive correlation with the fractures quantity,and fractures are most abundant where dolomite content up to the maximum in core. For Yuye-1 well, shale mineralogy is low degree of discrete with strong homogeneity, therefore, the development and distribution of fractures are controlled by TOC, moreover, the TOC shows positive correlation with the fractures quantity. Fractures are sealed by calcite, quartz and pyrite. Although sealed fractures do not contribute to the permeability of the reservoir, they are important planes of weakness that tend to be reactivated by hydraulically induced fractures. SEM show that intergranular pore is connected by microfractures, thereby, the validity of porosity had been improved.The mixed network of microfractures and micropore provide enhanced permeability or storage capacity for the reservoir.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013