The accumulation of natural gas and potential exploration regions in the southern margin of the Junggar basin
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    Abstract:

    The southern margin of the Junggar basin has the similar history of sediment and tectonic evolution with the Kuqa depression of Tarim basin, but has never made a great breakthrough in natural gas exploration. Based on the results of genetic type and origin of the natural gas, this paper discusses the conditions for natural gas generation and accumulation compared with the Kuqa depression, and the favorable exploration regions and potential target in the region. The results show that the natural gases in the southern margin are dominated by thermogenic wet gas, which are divided into three types, coal- derived gas, mixed gas and oil- associated gas, and are dominated by former two types. The Jurassic coal measures is the main natural gas source rocks in the southern margin, and its main period of gas generation matches the formation epoch of the anticline structures, which constitutes the best source- trap combination for gas accumulation. The Permian lacustrine and Upper Triassic lacustrine- limnetic facies source rocks may also be important natural gas source rocks, whose main period of gas generation is earlier than the formation epoch of most anticline structures in the central region, but coincides with the epoch of anticline formation in the western region. Compared with the Kuqa Depression, the southern margin has batter material base of hydrocarbon generation than the Kuqa depression, but the maturity of the source rocks of the Jurassic coal measures is slightly lower than that of the Kuqa depression, the capping of the caprock and the scale of reservoir rock are slightly inferior to those of the Kuqa depression. The southern margin still has the conditions for forming large- scale oil and gas fields. The combination of the Permian- Jurassic- Cretaceous in the deep is the most favorable system for natural gas exploration, where the western part is a favorable target area for finding and discovering Jurassic coal- derived oil and gas reservoirs, and the middle part is a favorable target area for finding and discovering Jurassic coal- derived gas reservoirs. The combination of the Cretaceous- Neogene in the shallow is a secondary system for natural gas exploration, with the potential to find and discover a certain scale of natural gas reservoirs. The natural gas in the Qingshuihe oil and gas reservoir of the well Gaotan- 1 is a mixture of coal- derived gas and oil- associated gas, of which the Jurassic and Permian contributions account for about half each. The great breakthrough in oil and gas exploration in the well Gaotan- 1 indicate that the factors that restrict the discovery of natural gas in the southern margin are not the gas source scale, migration path, reservoir properties and caprock sealing, but the identification of effective traps, drilling technology and exploration workload.

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CHEN Jianping, WANG Xulong, NI Yunyan, XIANG Baoli, LIAO Fengrong, LIAO Jiande.2019. The accumulation of natural gas and potential exploration regions in the southern margin of the Junggar basin[J]. Acta Geologica Sinica,93(5):1002-1019

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History
  • Received:April 12,2019
  • Revised:April 19,2019
  • Adopted:
  • Online: April 20,2019
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