World Recoverable Unconventional Gas Resources Assessment Chapter uri icon


  • 2016 Elsevier Inc. All rights reserved. For over 50. years, oil and gas companies in North America have been developing technology to produce from unconventional gas resources. During this time, developments in exploration, drilling, completions, and stimulation have led to what is now called the shale revolution. There are publications in the literature describing the volume of the resources (gas in place) in many of the plays in many of the basins. However, the industry is most interested in how much natural gas can be recovered using state of the art technology, which is called technically recoverable resources. Some publications address technically recoverable resources (TRR) of unconventional gas in small geographic areas in North America. However, there is virtually no information published about the magnitude of TRR for unconventional gas on a global scale. Uncertainty exists in geologic and engineering data and, consequently, in the results of calculations made with these data. The uncertainty of the problem begs for a probabilistic solution.The objective of our work was to determine the distribution of unconventional gas TRR worldwide. To achieve this goal, a computer program, called unconventional gas resource assessment system (UGRAS), was developed. The program integrates a Monte Carlo technique with an analytical reservoir simulator. The combination provides an excellent means to predict production profiles for a wide variety of reservoir characteristics and producing conditions. Using UGRAS, the probabilistic distribution of original gas-in-place, TRR, and recovery factor for selected unconventional gas reservoirs in the United States were established and the representative distribution of recovery factors for those unconventional gas reservoirs were derived. Finally, the distribution of recovery factors gained from the analyses of unconventional gas reservoirs in the United States was extended to estimate global unconventional gas TRR.UGRAS is a robust tool that may be used to evaluate and rank shale gas, tight gas, and coal bed methane (CBM) resources worldwide. Results of this work verify the existence of significant technically recoverable unconventional gas resources worldwide and can guide industry better target its exploitation efforts worldwide.Global CBM TRR was estimated from 500 (P90) to 3000 (P10) trillion cube feet (Tcf). Global tight gas TRR ranges from 37,000 (P90) to 80,000 (P10) Tcf and global shale gas TRR ranges from 4000 (P90) to 24,000 (P10) Tcf.

author list (cited authors)

  • Dong, Z., Holditch, S. A., & John Lee, W.

Book Title

  • Unconventional Oil and Gas Resources Handbook

publication date

  • January 1, 2016 11:11 AM