南美前陆盆地古生界天然气成藏特征及勘探潜力分析

基于对Chaco盆地的详细解剖，通过分析其古生界天然气的成藏条件和成藏特征，总结其成藏主控因素，进而类比和分析南美前陆盆地古生界天然气的成藏特征和勘探潜力。Chaco盆地天然气资源丰富，为南美天然气储量最大的盆地，且天然气资源主要集中在古生界；其古生界天然气成藏模式优越，成藏具有优生、多储、圈闭规模大、新生古储、多期成藏、近源成藏及集中分布的特征，天然气成藏受主力成藏组合和断裂的双重控制。由于构造演化的差异，南美前陆盆地古生界有效储层仅在中部3个盆地发育；除Chaco盆地外，其他2个前陆盆地古生界与Chaco盆地具有相似的天然气成藏条件，成藏背景有利，具有一定的勘探潜力。研究指出Chaco盆地古生界天然气勘探程度较高，下一步勘探仍以次安第斯带和前渊带泥盆系为主要目的层系，兼探深层和斜坡带浅层非构造圈闭。Beni盆地和Madre de Dios盆地古生界勘探程度非常低，下一步应加强断裂最为发育的次安第斯带和前渊带的勘探力度，以构造圈闭为最有利勘探目标。

The Exploration Potential and Accumulation Characteristics of Paleozoic Gas of Foreland Basins in South America

In order to analyze and point out the Paleozoic gas reservoir characteristics and exploration potential of South American foreland basins,the Chaco basin was taken as an example in this paper.By analyzing the Paleozoic gas reservoir accumulation conditions and characteristics,the main factors of gas accumulation were summarized.The Chaco basin is the largest basin of gas resources in South America,and gas is mainly concentrated in the Paleozoic.The gas accumulation conditions of Paleozoic reservoir in Chaco basin are very good,which have the characteristics of excellent source rocks,multi-reservoirs,large-scale traps,younger source rock-older reservoir,multi-phase and near source accumulation and centralized distribution.The gas accumulation is mainly controlled by the main plays and faults.Due to the differences of tectonic evolution,the Paleozoic reservoirs of South America foreland basins are only developed in the three basins in central South America.With favorable background of gas accumulation and certain amount of exploration potential,the two other Paleozoic foreland basins have a similar gas accumulation conditions with the Chaco basin.This study pointed out that the exploration of Paleozoic gas in the Chaco basin reached a higher degree.As to its exploration in the future,the sub-Andean belt and fore deep are still the main plays,and Devonian is still the main stratum,considering the non-structural traps of deep strata in the fore deep and shallow strata in the slopes.The Paleozoic of the Beni basin and the Madre de Dios basin has very low degree of exploration,so more consideration should be given to the sub-Andean belt and fore deep area in the next step,where faults are the most developed and structural traps are the most favorable exploration targets.