Hydraulic fracture quality from time lapse VSP and microseismic data

Abstract

The ability to produce from low permeability, tight gas reservoirs is directly tied to the ability to repetitively perform successful hydraulic fracturing in a series of closely spaced wells. The key question is whether the induced fractures remain open and permeable, which is in part a function of the stress field and the emplacement of proppant. We study the ability to detect and characterize hydraulic fractures from scattered seismic energy. A 3D VSP forms the reference for seismic reflectivity before hydraulic fracturing. During the hydraulic fracturing the microseismic events are recorded and then the arrival times picked and the events located. Another 3D VSP survey is recorded after the fracture treatment. The difference between the VSP surveys yields a 3D time lapse VSP dataset which contains the changes in the reflected wavefield and the addition of scattered energy. The microseismic moveout times can be used to extract from the time lapse VSP data the seismic energy scattered from the induced fracture planes. We show the encouraging results from both model and field data.