ESTIMATING BRITTLENESS USING SEISMIC DATA IN AN UNCONVENTIONAL SHALE RESERVOIR, FORT WORTH BASIN, NORTH CENTRAL TEXAS

Abstract

Brittleness within unconventional shale plays is a major component in reservoir stimulation. Mineralogy measured in nearby wells estimates brittleness and can be correlated to elastic parameters measured in well logs and surface seismic data. Brittle zones are dominated by high quartz and TOC while ductile zones are dominated by clay and calcite with lower TOC. λρ and µρ calculated from prestack inversion seismic data predictes brittle and ductile zones, which is validated using microseismic data. Near the heel of the well, many microseismic events propagated into the more ductile Forestburg limestone. Using a borehole image log, it appears that open and partially open fractures allow perforation energy to travel into the overlying more ductile formations. Near the toe of the well events occur in the more brittle areas of the target Barnett Shale formation. Correlating fracture type with curvature, low (near zero) values of most positive curvature are highly fractured and contains the most microseismic activity. Creating a brittleness volume, microseismic events occur in brittle and less brittle zones with the exception of the events that occur in the ductile Forestburg limestone due to an increase in open and partially open fractures towards the heel of the well.