Accummulation conditions and key technologies for exploration and development of Zhongjiang gas field in Sichuan Basin

The Jurassic reservoir in the eastern slope belt of western Sichuan depression is generally characterized by "dual-source" hydrocarbon supply of the high-quality source rocks from the Member 5 of Upper Triassic Xujiahe Formation and the Lower Jurassic, development of multi-stage, multi-set, superimposed channel sandstones in a large scale, hydrocarbon supply owing to the continuous activity of faults connecting source rock, and favorable conditions for configuration of the ancient and present faults and sand bodies. Thus, it has the geological conditions and temporal-spatial combinations of source and reservoir for forming a tight sandstone gas field. By summarizing and analyzing the geological conditions of the reservoir in Zhongjiang gas field, this paper proposes a new understanding that the reservoir in Middle Jurassic Shaximiao Formation is characterized by development of channel-controlled sand bodies, hydrocarbon transportation through faults and sand bodies, and accumulation under superposition and compound condition, and establishes the enrichment pattern with the characteristics of continuous fault activity, multi-period hydrocarbon charging, lithologic gas reservoir development and hydrocarbon enrichment far from faults. Based on the exploration and development of Zhongjiang gas field, key supporting technologies have been formed, such as the fine characterization technology of "sweet spots" of tight sandstone gas, high-efficient development technology for tight sandstone gas reservoir in complex narrow river channel, and dense cutting and strong-support volume fracturing technology of horizontal well. Through the integrated operation of geology and engineering, Zhongjiang gas field, as a tight sandstone gas field in the narrow river channel of Shaximiao Formation, has provided a cumulative proved reserve of natural gas of more than 100 billion cubic meters, with the gas output of over 20×108m3/a. © 2022, Editorial Office of ACTA PETROLEI SINICA. All right reserved.