雪峰山西侧地区海相油气勘探前景初析

通过对雪峰山西侧地层叠覆关系、沉积序列、层序地层和旋回沉积特征等油气地质的调查研究,表明雪峰山西侧盆地演化与四川盆地一样,均经历了从被动陆缘(Z-O₁)→类前陆(O₂-S)→克拉通-大陆边缘盆地(D-T₂)→内陆湖盆(T₃-J)和山间盆地(K-Q)5个演化阶段;发育9个区域性平行不整合和1个角度不整合,构成5个构造层,即①南华系-震旦系;②下古生界;③上古生界-下中三叠统;④上三叠统-下中侏罗统;⑤上白垩统及其以上。总体构造活动性不强,对油气长期保存和演化有利。5个构造层孕育了4个一级生储盖组合,其中Ⅰ、Ⅱ为有利组合。因此,该地区原生油气地质条件优越,但后期改造较强,特别是侏罗纪末期的燕山运动以来的造山和隆升剥蚀量大,是该区海相下组合油气勘探的制约性因素。

An approach to the oil and gas exploration potential in the marine strata in the western part of the Xuefeng Mountains,southern China

The examination of stacking patterns,sedimentary sequences,sequence stratigraphy and cyclic deposition in the western part of the Xuefeng Mountains,southern China shows that just like the Sichuan Basin,the western part of the Xuefeng Mountains has gone through the basin evolution from the passive continental margin(Z-O1) through the forelandoid basin(O2-S) to the craton-continental marginal basin(D-T2) and the inland lake basin(T2-J),and finally to the intermountain basin(K-Q).Nine reginal parallel unconformities and one angular unconformity are observed,constituting five tectonic terranes,including: ① the Nanhuan to the Sinian;② the Lower Palaeozoic;③ the Upper Palaeozoic to the Lower-Middle Triassic;④ the Upper Triassic to the Lower-Middle Jurassic,and ⑤ the Upper Cretaceous or younger.In the above-mentioned tectonic terranes,there occur four first-order source-reservoir-seal associations,of which Associations I and II are believed to be favourable.The study area was originally in the favourable geological conditions,but there after underwent severe tectonic modification,especially the mountain building,uplifting and denudation from the Yanshanian movement at the end of the Jurassic onwards.It follows that the tectonic modification cited above are considered as the controlling factors of the oil and gas exploration in the marine lower association in the study area.