SRV Estimation Using Hydraulic Fracture Microseismic Event Data

A significant source of unconventional hydrocarbons is shale gas reservoirs. These reservoirs are unconventional in that they are low porosity and permeability, hence making recovery difficult. The implementation of fracturing stimulation is the key to producing these reservoirs. Knowledge of the effectiveness of the hydraulic fracture treatment is important both in terms of planning future treatments and also for assessing the success of the treatment and expected recovery. The effectiveness of the treatment is related to the volume of the reservoir that has been altered (permeability-enhanced) by the fracturing treatment – i.e. the estimated SRV. Microseisms are generated during the hydraulic fracturing process and these data can be analyzed to provide an estimate of the SRV since their locations represent the reservoir space which has been contacted by the fracturing treatment. Three methods are described for calculating the SRV from microseismic data: the Delaunay triangulation method, a rectangular voxel-based approach and a trapezoidal method. The results show a range in the calculated SRV values, indicating the uncertainty in the estimate yet providing a basis for the magnitude that may be expected.