Sweet Spot Mapping of the Barnett Shale Play, Fort Worth Basin, Texas

Fu, Qilong; Horvath, Susan; Potter, Eric; Roberts, Forrest; Tinker, Scott; Fisher, William

This study characterizes the Barnett Shale play in the Fort Worth Basin by log-based sweet spot mapping. We employ a porosity-footage (PHI*H) map to identify sweet spots. The key data are digital logs from 146 selected wells based on availability of gamma-ray and density curves, log quality, and good spatial distribution. One important step for sweet spot mapping involves determining the pay zone within the Barnett Shale Formation. In the middle and southern part of the study area, the whole Barnett interval is considered as the pay zone. In the northern part, only the lower portion of the Barnett Shale is counted as pay zone. The pay zone is picked based on (1) density log porosity (DPHI) > 5%, (2) high GR (commonly > ~100 API units), and (3) no significant carbonate-rich beds (< ~10-15 feet). The Barnett pay zone varies from about 107 to 434 feet in thickness. Density log porosity is a primary proxy to gas shale reservoir quality, and average DPHI of individual wells for the Barnett pay zone ranges between 7.0% and 14%. Our porosity-footage map shows that areas with high PHI*H values (i.e. sweet spots) coincide largely with those with relatively high natural gas production. An exception is the northernmost part of the study area that is located in wet gas to oil window. The pattern of sweet spot map for the Barnett Shale play mimics that of the thickness isopach map for the Barnett pay zone, suggesting that thickness or storage volume is the major driver of sweet spot locations.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013