Critical conditions for natural gas charging and delineation of effective gas source rocks for tight sandstone reservoirs

• Published in: Geological journal (Chichester, England) England), 2016-01, Vol.51 (1), p.113-124
• Main Authors: Jiang, Fujie, Pang, Xiongqi, Guo, Fengtao, Guo, Jigang
• Format: Article
• Language: English
• Subjects: effective gas source rock; force balance; gas charging condition; resource potential; tight-sand gas
• ISSN: 0072-1050; 1099-1034
• DOI: 10.1002/gj.2614

Although it has been shown that the potential of tight‐sand gas resources is large, the research into the mechanisms of hydrocarbon charging of tight sandstone reservoirs has been relatively sparse. Researchers have found that there is a force balance during hydrocarbon charging, but discriminant models still have not been established. Based on the force balance conditions observed during gas migration from source rocks to tight sandstone reservoirs, a calculation formula was established. A formula for identifying effective source rocks was developed with the gas expulsion intensity as the discrimination parameter. The critical gas expulsion intensity under conditions of various burial depths, temperatures, and pressures can be obtained using the calculation formula. This method was applied in the Jurassic tight sandstone reservoirs of the eastern Kuqa Depression, Tarim Basin, and it was calculated that the critical expulsion intensity range from 6.05 × 108 m3/km2 to 10.07 × 108 m3/km2. The critical gas charging force first increases with depth and later decreases with greater depths. The distribution range of effective gas source rocks and total expelled gas volume can be determined based on this threshold. This method provides new insight into and method for predicting favourable tight‐sand gas‐bearing regions and estimating their resource potentials. Copyright © 2014 John Wiley & Sons, Ltd.