Mechanical and Elastic Characterization of Shale Gas Play in Upper Indus Basin, Pakistan

Abstract

The organic-rich shale intervals of Patala Formation of Paleocene age may be considered as potential shale gas play in the Upper Indus Basin of Pakistan. Until now, seismic and elastic properties of the Patala shales are not investigated in detail necessary to declare it as shale gas play and to differentiate shale gas pay zone from the non-pay zone. Data of eight wells in which Patala shales were encountered at various depth levels from 2000 to 4300 m were deeply investigated for shale gas characterization. This shale fulfills the basic criteria of organic-rich shale with TOC ~ 0.5–5.8%, vitrinite reflectance (level of maturity) is 0.6–1.7%, average thickness 48 m. The brittleness index (BI) of this organic-rich shale was computed by using effective mechanical properties and mineralogy to define brittle zones in the shale intervals preferable for generating the fracture network. BI data points demonstrate that a large number of values fall in the brittle zone, whereas fewer values fall in the ductile zone. However, a certain number of values fall in the brittle–ductile transition zone. The quantitative comparison between different elastic and seismic properties derived from the wireline logs guide for the delineation of the pay zone from the non-pay zone in the organic-rich shale intervals.