Impact of organic contents and brittleness indices to differentiate the brittle-ductile transitional zone in shale gas reservoir

Abstract

The economic success of shale gas plays depends expansively on the brittle-ductile behavior of shale rock for effective hydraulic fracturing. Successful hydraulic fracturing requires targeting the most brittle rocks. Therefore it is worthwhile to classify the shale regarding brittle and ductile zones. To study the impact of brittleness indices in the brittle-ductile transitional zone, we have estimated the mineralogy-based brittleness index, TOC (total organic carbon), pore pressure and geomechanical properties from well logs and core description laboratory measurements. The petrophysical model of Sembar shale from Indus basin Pakistan was compared to brittleness index, organic contents, and pore pressure to differentiate the transitional zones in shale gas reservoirs. The result shows that constant change in rock minerals distribution and brittleness index follow the trend in TOC content, in brittle- ductile and transitional zone. Also, the data was plotted in λρ-μρ lithology templates and plots of Young’s modulus and Poisson’s ratio, shale with high quartz and clay contents trap in less ductile to less brittle zone while shale with abundant quartz and low clay contents give rise in the brittle zone. The observations of this study support the previous research idea by suggesting the zones of brittle and transition controlled by TOC to design the hydraulic fracture more efficient.