Identification of brittle and ductile zones in sandstone reservoir using well log analysis; a case study, Southern Indus Basin, Pakistan

Brittleness and ductility play a very important role in the stimulation design of unconventional reservoirs as it controls the fracture length and shape of hydraulic fractures. The estimation of mechanical properties of the reservoir rock is very important for the successful execution of reservoir drilling, production, and development operations. In this study, the mechanical properties are calculated using well log responses for selected reservoir section after a quality check of the data. Brittleness is estimated from empirical correlations based on mechanical properties estimated from well logs response, uniaxial compression strength and tensile strength. High values of young modulus and corresponding low values of Poison's ratio were indicating the brittle zones in the reservoir. Brittle-ductile zone identification based on mechanical properties were giving consistent results. Brittle-ductile categorization is done for identification of brittle, less brittle, less ductile and ductile reservoir lithology in each studied well. It was found from the computer-assisted approach and graphical presentation that, there was a high brittleness in the lower part of the reservoir which is due to highly compressed shale formation. This part of the reservoir could be a good candidate for hydraulic fracturing if it satisfies all other constraints for a prospective reservoir. (paper)