从苏北盆地黄桥和朱家墩气田成藏特征看江汉盆地勘探前景

苏北盆地发育了“黄桥型”和“朱家墩型”两类气藏。黄桥型气藏为断裂—裂缝型复合圈闭,不受层位控制,其气源为具有晚期生烃潜力的海相烃源岩重新深埋后再次生成的烃类气和经多期次火成岩侵入和喷发产生的大量CO2。朱家墩型气藏主要是海相烃源岩深埋后二次生烃形成晚期烃源充注、向上运移到白垩系成藏,属“古生新储”型。江汉盆地的成藏条件与苏北盆地具有可对比性,其中的江陵凹陷具备形成黄桥型气藏的条件,而沔阳凹陷则具备形成朱家墩型气藏的条件。江陵凹陷与苏北黄桥气田在构造演化、储盖条件、烃源、岩浆活动等方面均具有相似性,且前者的成藏条件更显优越。沔阳凹陷与苏北盐城坳陷东南部的烃源岩基础数据具有可比性,古生界均具备多套烃源岩层,且均表现为高演化特点,晚期生烃潜力也相似,其烃源为晚期生烃的古生界和上三叠统—侏罗系。

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.