Integrated Seismic and Petrophysical Characterization of the Barnett Shale in South-West Fort Worth Basin
While significant information on petrophysical properties and structural control of the Barnett Shale play has been reported in the high-producing core areas of the Fort Worth Basin, little has been reported on properties that lie at the basin fringe. Here, we present a post-mortem of a high-quality, wide-azimuth survey acquired in the south-western part of the Fort-Worth Basin. In this area the Barnett Shale is about 200 ft thick and occurs in the depth range of 3500 ft to 5000 ft. Analyses of surface seismic data calibrated with wireline logs helped to track the fine-scale variations of the Barnett Shale and correlated to a suite of conventional as well as more recently-developed seismic attributes to identify and quantitatively analyze the complex discontinuity patterns along with stratigraphic changes within the Barnett Formation. Significant impedance contrast between the Barnett Shale and adjacent limestone units facilitate identification of the vertical limits of the Barnett Shale; however the collapse structures and presence of basal conglomerates decrease the relative impedance contrast between the Barnett and the underlying Ellenburger in some places. Multi-attribute analyses of the surface seismic data provided a means to regionally track fault and fracture systems. Calibration of such analyses with the high-resolution borehole image log-based fracture analyses allowed us to further classify the fracture systems. Fracture analyses based on high-resolution borehole image logs revealed three types of natural fractures: open, partially-filled and closed along with drilling-induced fractures. Overall, the Barnett Shale is characterized by 2°- 4° structural dip except in the areas adjacent to faults where it approaches 12°. Borehole-image data also indicate that the maximum horizontal stress is oriented northwest-southeast.
The Barnett Shale is characterized by plane laminated mudstone along with some concretions. Stratigraphic changes coupled with changes in the deep resistivity were useful for detecting potential hydrocarbon-rich intervals. Extending the petrophysical analysis from the Barnett target interval, as well as to the Ellenburger, and Marble Falls frac barriers to seismic volume through prestack impedance inversion are critical to high-grade potential reservoir intervals and guide reservoir completion technologies.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California