改造型盆地与天然气勘探

REFORMATION BASIN AND NATURAL GAS EXPLORATION

随着油气工业的发展，天然气勘探将面对更深、更复杂的领域———改造型盆地。所谓改造型盆地是指形成较早、在其后的地质历史中受到较强烈剥蚀、变形并且叠加、深埋等改造作用的沉积盆地。与盆地改造相应的是油气生成、运聚的变化，多次生烃、成藏，古油气藏部分或全部被破坏以及次生油气藏的形成等。通过对我国主要含油气盆地改造状况的分析归纳，认为依据改造程度，可将我国４４个主要含油气盆地分为五大类：①上覆为基本未被剥蚀的原型盆地，下伏为保存大致完好的简单断陷或断坳结构；②上覆为基本未被剥蚀的原型盆地，下伏为复杂结构盆地，其中部分为剥蚀残留盆地，但构造破坏微弱；③上覆层已受到轻微剥蚀破坏，下伏层中主力生储岩系受到一定程度剥蚀分割和构造破坏；④上覆层受到严重的剥蚀分割，主力生储层系受到严重破坏；⑤全盆地各沉积层系均受剥蚀和构造破坏，常被分割成盆地群并被地下水氧化破坏。在此基础上提出下世纪天然气勘探总体指向有二：一是东部的挖潜和向新区带、新领域的开拓；二是中、西部的主要含气盆地。而不论是哪一个方向，其重点都是向勘探难度更大的改造型盆地发展。

Along with the development of petroleum industry,the deeper and more complicated domainthe reformation basin will be faced in natural gas exploration.Socalled reformation basin means such a sedimentary basin which was formed relatively early,then suffered a strong degradation,deformation,superposition and deep burying in its later geological history.The basin reformation could lead to the change in the oil and gas generation and migration,repeated hydrocarbon generation and reservoir formation,partial and entire destruction of ancient oil and gas reservoirs and the formation of secondary reservoirs,etc.Through analyzing and summarizing the reformation circumstances of the main oiland gasbearing basins in China,it is considered that according to the degree of reformation,the 44 main oiland gasbearing basins in China may be divided into five categories:the overlying is the prototypical basin with a little degradation and the underlying is the relatively full structure of simple fault depression or fault sag;the overlying is also the prototypical basin with a little degradation and the underlying is the basin with complicated structure,of which part being the denuded remnant basin with a slight destruction by tectonism;the overlying suffered a slight destruction by denudation and the major sourcereservoir rock series in the underlying strata suffered degradation and division to a certain degree and were seriously destroyed;all the sedimentary rock series in the whole basin were denuded and destroyed by tectonism,the basin being always subdivided and destroyed by ground water oxidation.On the basis of this,an overall trend of natural gas exploration in the next century is proposed as follows:one is to tap the latent potentialities in the old fields and to open up the new prospective zones and new domain in the East China;the other is the main gasbearing basins in the West China.No matter which it is,the focal point is to carry out the exploration work in the reformation basin with more complicated circumstances.