负压地层形成机制及其对油气藏的影响

Formation Mechanism of Underpressure Strata and Its Effect on Oil-Gas Accumulation

具异常压力场特征的盆地在我国比较普遍 ,但更多的是研究超压体系 ,对于异常低压体系的成因与机制在国内还没有很好的解释。盆地内的广泛沉积造成的巨厚沉积地层 ,并在随后的地层抬升过程中造成的严重剥蚀 ,导致剥蚀反弹现象 ,从而形成负压区。由于地层的温度或其他因素的影响 ,也会造成局部的负压现象。根据百色盆地的负压现象 ,从其成因着手 ,分析其形成过程及其对该地区油气藏的影响。负压造成流体的局部回流 ,形成低压封隔窗 ,促使油气二次运移 ,从而改造油气藏的分布 ,形成一些与负压有关的油气藏。

Basins with abnormal pressure characteristics are numerous in China; nevertheless, up till now, studies have been mainly focussed on the overpressure system, and insufficient attention has been paid to the abnormal underpressure system. Extensive deposition within the basin results in strata of great thickness, and the uplifting procedure of sedimentation leads to serious erosion and the erosional unloading phenomenon, finally forming the underpressure area. There are of course many other factors such as temperature of the strata which can produce underpressure. It is therefore very important to consider all the factors in an integrated way in the exploration of the underpressure basin. This paper deals with the underpressure of Baise basin and analyses its formation and its effects on oil-gas accumulation. Underpressure causes regional back flow of fluids, forms underpressure seal windows, stimulates the second oil gas transition, thus affecting the distribution of oil gas reservoirs and forming some oil gas accumulations associated with underpressure.