Oil & Gas Geology ›› 2022, Vol. 43 ›› Issue (1): 161-174.doi: 10.11743/ogg20220113

• Petroleum Geology • Previous Articles     Next Articles

Genetic types and exploration potential of natural gas at northwestern margin of Junggar Basin

Deyu Gong1(), Changyong Zhao2, Wenjun He3, Long Zhao3, Yumei Kong4, Liya Ma1, Ruiju Wang1, Wei’an Wu1   

  1. 1.Research Institute of Petroleum Exploration & Development,PetroChina,Beijing 100083,China
    2.Exploration Department of Xinjiang Oilfield Company,PetroChina,Karamay,Xinjiang 834000,China
    3.Petroleum Exploration and Development Research Institute of Xinjiang Oilfield Company,PetroChina,Karamay,Xinjiang 834000,China
    4.Geophysical and Geological Division,Hebei Coalfield Geological Bureau,Xingtai,Hebei 054000,China
  • Received:2021-08-13 Revised:2021-12-12 Online:2022-02-01 Published:2022-01-28

Abstract:

Although the Junggar Basin is one of the four major onshore petroliferous basins in China, the progress of natural gas exploration is poor with major discoveries confined to the eastern and southern parts of the basin. Based on gas composition and stable carbon isotopes, we find four types of natural gas at the northwestern margin of Junggar Basin. TypeⅠgas is primarily generated from the lacustrine source rocks of the Lower Permian Fengcheng Formation, and can be further subdivided into TypeⅠA (mainly derived from Shawai Sag) andⅠB (mainly from Mahu Sag). Type Ⅱgas is mainly of coaliferous gas derived from the Carboniferous and Lower Permian Jiamuhe humic source rocks of high to over-mature type in the Shawan Sag. Type Ⅲ gas is a mixture of TypeⅠandⅡ. Type Ⅳ gas is of secondary biogenic gas with oil biodegradation under reservoir destruction. During the Cretaceous, a mass of coaliferous and petroliferous gases were derived from the Fengcheng, Jiamuhe and Carboniferous source rocks in the Shawan Sag, which then migrated to higher parts of the structure along the carrier system composed of faults and unconformities; while the Fengcheng source rocks in the sag was at oil generation peak during which only a small amount of petroliferous gas of low maturity could be generated and accumulate within or over margins of the sag. In this study, it is confirmed that two suites of effective gas source rocks of large scale were developed in the Upper Paleozoic, west of Junggar Basin, that is, the Carboniferous (including Jiamuhe Formation) and Fengcheng Formation source rocks, serving to shed lights on a new field of natural gas exploration. In all, the study is of a typical case to show gas-source correlation under complex geological conditions and hydrocarbon accumulation restoration, and also deepens the understanding of the exploration potential of natural gas in the Junggar Basin.

Key words: carbon isotope, genesis and origin, exploration potential, natural gas, Junggar Basin

CLC Number: