向斜下中和面构造油气藏——中国南方海相中-古生界油气勘探新方向

在褶皱地层中部既无伸长亦无缩短的无应变面为中和面,其上地层称上中和面,其下地层称下中和面。背斜构造的上中和面和向斜构造的下中和面处于张应力状态(T),为有利的油气储集区域;而背斜下中和面和向斜上中和面则处于压应力状态(C),属于油气排出区域。油气从C区域向T区域运移成藏,称"C—T"成藏模式。中国南方海相中、古生界的背斜构造几乎都遭受剥蚀,背斜上中和面油气构造已被破坏。但是向斜下中和面构造仍保存完好,且随着上覆地层被剥蚀,埋藏变浅,易于对其进行商业勘探。我们可以改变思路,以向斜下中和面构造油气藏为中国南方海相中、古生界的勘探新方向。

Hydrocarbon Accumulation Below the Syncline Neutral Surface:A New Prospecting Target of Petroleum Exploration in Mesozoic-Paleozoic Marine Formations in Southern China

The stratigraphic neutral surface of a folded bed means neither elongated nor shortened a non-strain plane, above which it is called upper neutral surface and below which it is called lower neutral surface. The places where the upper neutral surface of an anticline and the lower neutral surface of a syncline are in a status of tensile stress(T) are the favorable hydrocarbon-gathering areas,while the places where the lower neutral surface of an anticline and the upper neutral surface of asyncline are in compressional zone (C) are the hydrocarbon-discharged areas. If hydrocarbon is migrated from the compressional zone to the tensional area, it is defined as "C-T" accumulation model. In the Mesozoic-Paleozoic marine formations in southern China, anticlines are almost exposed to denudate and traps, i.e. the upper neutral surface of anticlines, are commonly destroyed but the lower neutral surface of buried synclines keeps intact yet and gets shoaling with denudating of overlying,which brings in getting easy for commercial oil prospecting. Therefore we can change our idea to prospect for the lower neutral surfaces of synclines,which may be able to become new petroleum prospecting targets in Mesozoic-Paleozoic marine formations in southern China in future.