Barnett Shale is a major hydrocarbon source rock in the Fort Worth basin. As one of the most fully developed shale gas plays in North America, knowing the fracture orientation and density in Barnett shale is critical for fracturing during horizontal drilling. In our study, the main objective is to predicate the azimuth and density of natural fractures of the Barnett Shale.
We migrate our seismic data by a new binning approach that sort the data by azimuth. We calculate AVO gradient from prestack gathers for each azimuth bin. By comparing the azimuthal AVO gradient variation, we generate the AVO gradient anisotropy for prediction of natural fractures.
Strike-slip faults are known to modify the subsurface stress regime. We map faults using both the strike and magnitude of the most-positive and most-negative principal curvatures and visually correlate them to AVAz. There is high correlation between positive curvature and high anisotropy density. Finally, we generate a vector correlation between AVAz and the two curvatures, and find that perpendicular relationship between the most negative curvature and AVAz vector.
The Fort Worth Basin has been the interested object so far, because its role as one of the most important early shale gas plays. Although high TOC property of Barnett Shale makes it a good source rock, it is characterized by low permeability. Hydraulic fracture is required to provide pathways for fluid flow and increase the permeability. It has been a problem for the choice of the fracturing, so accurately mapping the density and azimuth of natural fractures and stress field can be essential for the production and horizontal hydraulic fracture choice.