高、低煤阶煤层气藏成藏过程及优势地质模型

在构造演化研究的基础上,对比了典型的高、低煤阶煤层气藏的形成过程,探讨了决定现今煤层气藏富集程度的关键因素。高煤阶煤层气藏由于生气量足,成藏过程复杂,通常经历了多次沉降、抬升及改造,到最高演化程度后就不再有煤层气的生成,其形成具有明显的阶段性,故现今煤层气的富集程度主要取决于保存条件;而低煤阶煤层气藏成藏过程简单,煤层形成后一般只经历了一次沉降,一次抬升,受现今地下水的补给、运移、排泄和滞流的控制作用。基于以上认识,分别建立了封闭系统高煤阶煤层气藏优势地质模型和盆缘缓坡低煤阶煤层气藏优势地质模型。

Formation Processes and Advantageous Models for High-Low-Rank Coalbed Methane Reservoirs

The typical formation processes of high-low rank coalbed methane (CBM) reservoirs are presented based on tectonic evolution extents. The key factors controlling current accumulation and enrichment of CBM reservoirs are discussed. The study shows that the high rank CBM reservoir is of obvious episode for it normally undergoes multiple subsidence, uplift and modification with sufficient CBM and complex forming process; the CBM is not generated till reaching its highest evolution. So its current accumulation and enrichment mainly depend on conservation conditions. The formation process of low rank CBM reservoir is often simple, just undergoing single subsidence, single uplift and gentle modification, and controlled by underwater supply, migration, drainage and detention. According to these understandings, the advantageous model of high rank CBM reservoirs with closed system and the advantageous model of low rank CBM reservoir with basinal margin or gentle slope area are developed.