龙门山造山带与川西前陆盆地的盆山耦合关系对油气成藏的控制作用

摘要

According to the geochemistry, field section and well logging, the basin-range coupling relationship between Longmen Mountain orogenic belt and Western Sichuan foreland basin was explained, control of the coupling relationship to hydrocarbon accumulation was discussed, and some suggestion were put forward to exploration and predication of favorable area by means of petrology, stratigraphic correlation and basin modeling. The results showed that the basin-range coupling relationship, which included the correspondence of falling and uplift, that of provenance and sediment and that of tectonic multi-screen and sedimentary cycle, was good in terms of sediment and structure; the sedimentary coupling relationship controlled the sediment thickness and thermal evolution, and influenced the vertical and lateral distributions of reservoirs, but the tectonic coupling relationship had decisive effect on the development of faults in orogenic belt and foreland basin, and the traps for oil/gas migration and accumulation; the basin-range coupling was multi-phase, and the center of sediment and falling and the spread sedimentary facies were continuous migration and multi-overlay; there were three-dimensional screen evolution accumulation models in deep, middle and superficial layers in Western Sichuan foreland basin. The predication of favorable area showed that the southern part of Zitong Depression was the favourable region of deep basin gas;superficial layer gas distributed in the middle and southern parts of the basin developed by palaeohigh; deep layer gas mainly distributed in the pinchout zone of the northern and middle strata of the basin.%综合地球化学、野外剖面和钻测井等资料,运用岩石学和地层对比、盆地模拟等方法,剖析了龙门山造山带和川西前陆盆地的盆山耦合关系,探讨了这种盆山耦合关系对油气成藏的控制作用,最后给出了勘探建议及有利区带预测.结果表明:龙门山造山带和川西前陆盆地在沉积和构造方面表现出良好的盆山耦合关系,具体表现在沉降与隆升的对应、物源与沉积的对应以及构造多幕性和沉积旋回性的对应等特征上；沉积耦合关系控制着烃源岩的沉积厚度及热演化程度,并影响着储层的垂向和横向分布,而构造耦合关系则对造山带和前陆盆地的断层发育以及油气运移和成藏所需圈闭具有决定性作用；盆山耦合呈多期性,具有沉积、沉降中心以及沉积相展布不断迁移和多期叠加的特征；形成了川西前陆盆地深、中、浅层的三维立体幕式演化成藏模式.有利区带预测表明:梓潼坳陷南端是深盆气的有利聚集区；浅层气主要分布在古隆起发育的盆地中、南段；深层气则多分布于盆地北部及中部地层尖灭带.