Influencing Factors of the Brittleness of Continental Shales Containing Shell Limestone Interlayer

Brittleness is important in the evaluation of fracturing ability shale reservoir and has a significant impact on gas exploration development. This paper discusses characteristics controlling factors brittleness continental Da’anzhai Member Ziliujing Formation Lower Jurassic age northeast Sichuan Basin. Continental lithofacies their associations were grouped into four main rock types: clayey shale, silty shell calcareous characterized by high clay content local enrichment carbonate minerals as whole. Compared with marine contained low siliceous minerals, large number limestone interlayers. Carbonate play an role shale. The interlayers mainly thickness several centimeters laminates thicknesses millimeters also observed. filled calcite. Due to dissolution process, bedding joints corrosion formed calcite layers. In content, microfractures developed. energy consumption required for maintaining fracture expansion was lower after fracturing; fractures greatly improved reservoir’s brittleness.