Frontier exploration in the Kuqa Depression, western China, has identified the continuous tight-sand gas accumulation in the Lower Cretaceous and Lower Jurassic as a major unconventional gas pool. However, assessment of the shale gas resource in the Kuqa Depression is new. The shale
succession in the Middle–Upper Triassic comprises the Taliqike Formation (T3
t), the Huangshanjie Formation (T3
h) and the middle–upper Karamay Formation (T2–3
k), with an average accumulated thickness of 260 m. The
high-quality shale is dominated by type III kerogen with high maturity and an average original total organic carbon (TOC) of about 2.68 wt%. An improved hydrocarbon generation and expulsion model was applied to this self-contained source–reservoir system to reveal the gas generation
and expulsion (intensity, efficiency and volume) characteristics of Middle–Upper Triassic source rocks. The maximum volume of shale gas in the source rocks was obtained by determining the difference between generation and expulsion volumes. The results indicate that source rocks reached
the hydrocarbon expulsion threshold of 1.1% VR and the hydrocarbon generation and expulsion reached their peak at 1.0% VR and 1.28% VR, with the maximum rate of 56 mg HC/0.1% TOC and 62.8 mg HC/0.1% TOC, respectively. The volumes of gas generation and expulsion from Middle–Upper
Triassic source rocks were 12.02 × 1012 m3 and 5.98 × 1012 m3, respectively, with the residual volume of 6.04 × 1012 m3, giving an average gas expulsion efficiency of 44.38% and retention efficiency of 55.62%.
Based on the gas generation and expulsion characteristics, the predicted shale gas potential volume is 6.04 × 1012 m3, indicating a significant shale gas resource in the Middle–Upper Triassic in the eastern Kuqa Depression.
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Gas generation and expulsion characteristics;
eastern Kuqa Depression;
Document Type: Research Article
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing, 102249, PR China
CNOOC Research Institute, Beijing, 100027, PR China
Sinochem Petroleum Exploration & Production Co., Ltd, Beijing, 100027, PR China
Petrochina Tarim Oilfield Company, Korla, 841000, PR China
Strategic Research Center of Oil and Gas Resources, Ministry of Land and Resources, Beijing, 100034, PR China
Publication date: October 3, 2014