China Petroleum Exploration ›› 2024, Vol. 29 ›› Issue (4): 45-60.DOI: 10.3969/j.issn.1672-7703.2024.04.004

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Geological characteristics and exploration potential of deep coal measure gas in Xishanyao Formation in Taibei Sag, Turpan-Hami Basin

Chen Xuan, Zhang Hua, Lin Lin, Liu Juntian, Gou Hongguang, Li Xinning, Cheng Yi, You Fan   

  1. Research Institute of Exploration & Development, PetroChina Tuha Oilfield Company
  • Online:2024-07-15 Published:2024-07-15

Abstract: The deep coal measure gas is a new field of petroleum exploration in Turpan-Hami Basin, but the study level is relatively low. Based on coal rock testing and basic geological data, the distribution, coal quality, reservoir properties, macro and micro coal petrology, gas source,and isothermal adsorption characteristics of coal seams in the Middle Jurassic Xishanyao Formation in Taibei Sag in Turpan-Hami Basin have systematically been studied, which support to identify the gas-bearing property of coal measure reservoir and its influencing factors,propose accumulation and enrichment conditions for the deep coal measure gas, establish enrichment and accumulation patterns, and predict exploration potential in Taibei Sag. The results show that: (1) The coal seams in the deep Jurassic Xishanyao Formation in Taibei Sag have a wide distribution area and a great thickness, which are characterized by medium-low rank, primary structure, well-developed cleavages, low ash content, low water cut, and rich vitrinite. (2) The coal reservoir has high porosity and permeability, which is insignificantly affected by burial depth. The gas logging anomalies are common in coal seam interval, and the reservoir has moderate-good adsorption capacity, showing characteristics of coexistence of free gas and adsorbed gas, rapid gas breakthrough during trial production, and complete gas compositions.(3) After hydrocarbon supply and charging in coal measure strata in Taibei Sag, two hydrocarbon accumulation patterns were formed, i.e.,adjustment type in forward structural zone, and self-generation and self-storage type in slope and subsag areas. (4) There are abundant coal measure gas resources in Taibei Sag, with resource volume of nearly 3×1012 m3 of the main coal seams in Xishanyao Formation. Based on the comprehensive evaluation of coal measure gas resource abundance, coal seam thickness, gas content, and preservation conditions, Wenjisang Structural Zone and Xiaocaohu South Slope are favorable areas for deep coal measure gas exploration.

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