Reservoir Characteristics of Huangqiao and Zhujiadun Gasfields in Subei Basin: Enlightening on Exploration Prospect of Jianghan Basin

Two types of gas reservoirs, Huangqiao and Zhujiadun namely, are developed in Shubei Basin. In Type Huangqiao, the reservoirs consist of fault-fissure traps in which there are no unified gas-water contacts and are not controlled by horizons. The gas of this type mainly comprises the hydrocarbon that is regenerated from deep-reburied marine source rocks with late hydrocarbon-generating potential, and the carbon dioxide that is generated by multiphase of igneous rock intrusion and eruption. In Type Zhujiadun, the gas is mainly the secondary-generating hydrocarbon that is derived from deep-reburied marine source rocks and late migrated and accumulated into the overlying Cretaceous traps. It is shown that the petroleum geologic conditions, such as tectonic evolution, reservoir/seal relationship, source rocks magma activities and late hydrocarbon-generating potential, in Jianghan Basin are similar and correlative to those in Shubei Basin. In Jianghan basin, gas reservoirs in Jiangling Sag have as favorable geologic conditions as Type Huangqiao while those in Mianyang Sag have as Type Zhujiadun.