四川盆地已知大中型气田成藏条件研究

RESERVOIR-FORMED CONDITION RESEARCH ON THE KNOWN LARGEMEDIUM GAS FIELDS IN SICHUAN BASIN

为指导大中型气田勘探．采用盆地数值模拟、峨眉地裂运动及古隆起圈闭动态演化等新理论、新方法，对四川盆地已知大中型气田的成藏条件、成藏机制及分布规律等进行了研究。研究认为，不同地区、不同层位的大中型气田有不同的成藏机制：川东区上石炭统气藏为二次成藏机制；威远上震旦统气藏为水溶气成藏机制；川西区上三叠统气藏为“高压流体封存箱”成藏机制。因此，不同地区应以不同的地质规律指导气田勘探。已知大中型气田的成藏条件表明，继承性古隆起、圈闭大、储层厚、烃源足和古侵蚀面等是控制大中型气田形成的主要地质因素。四川盆地属古老克拉通内部盆地，有进一步寻找大中型气田的前景。通过对天然气地质条件的分析、对比认为，盆地内加里东期古隆起的上震旦统、川东区上石炭统的复合型圈闭、川西及川中的上三叠统、川中及川东区的雷－１层是勘探大中型气田的新领域。

For guiding the exploration of large-medium gas fields, the reservoirformed conditions, reservior-formed mechanism and distributive laws of the known largemedium gas fields in Sichuan Basin are researched by use of the new theories and methods asbasin numerical simulation, Emei taphrogeny and palaeohigh trap dynamic evolution etc.Which shows that the large-medium gas fields in the various formations and areas have different reservoir-formed mechanisms: the gas reservoirs in Upper Carboniferous in EastSichuan belong to secondary reservoir-formed mechanism; the ones in Upper Sinian inWeiyuan belong to water-soluble gas reservoir-formed mechanism and the ones in Upper Triassic in West Sichuan 'belong to high pressure fluid mothballed box' reservoir-formed mechanism. So,the gas explorations in various areas should be guided by the different geologiclaws. The reservoir-formed conditions of the known large-medium gas fields show that themain geologic factors of forming large-medium gas fields are the inherited palaeohigh, bigtrap, rich hydrocarbon sources and fossil erosion surface etc. Sichuan Basin is a palaeo-intracratonic basin, being of the prospects of further surveying large-medium gas fields. It isrecognized by analysing and contrasting the gas geologic conditions that the new territories ofexplorating large-medium gas fields in Sichuan Basin are the Upper Sinian in Caledonian papaeohigh,the combination trap of Upper Carboniferous in East Sichuan,the Upper Triassic inWest and Centre Sichuan and the T2l1 1in Centre and East Sichuan.