The exploitation of unconventional (continuous) resource plays with horizontal drilling and fracturing techniques continues to spur renewed development in mature producing basins in the US. The Permian basin of west Texas has emerged as a particularly strong prospect due to the potential for multiple stacked resource plays in formations such as the Wolfcamp shale and Spraberry and Bone Spring formations.
Production began in the Permian basin in the early 1920s, and more than 116,000 wells have been drilled in Midland basin alone.1 2 In 2017, total Permian basin oil production climbed to nearly 1.7 million b/d.3
The US Geological Survey (USGS) conducts geologic-based assessments of undiscovered, technically recoverable domestic hydrocarbon resources. The USGS recently assessed the Wolfcamp shale in the Midland basin portion of the Permian basin for continuous (unconventional) oil and gas resources, and completed a reassessment of the Spraberry formation for both continuous and conventional oil and gas.4 5 Combined, the assessments of the Spraberry formation and underlying Wolfcamp shale in Midland basin comprise the largest domestic continuous oil assessment in the contiguous US (Fig. 1).