柴达木盆地阿尔金山山前带基岩气藏差异富集因素

基岩油气藏多分布在盆缘山前带,其形成与山前带隆升和断裂活动息息相关,具有差异成藏的特点。通过系统梳理阿尔金山山前带基岩油气成藏要素,结合国内外基岩油气勘探情况,总结了阿尔金山山前带基岩气藏差异富集规律。研究结果表明,阿尔金山山前带基岩油气成藏具有4大主控因素,一是存在多个侏罗系局部生烃中心,控制了阿尔金山山前带基岩气藏分布和丰度;二是阿尔金山山前带具有“隆起区、斜坡区、坳陷区”三大构造台阶,靠近生烃凹陷斜坡区的基岩圈闭油气优先充注、保存完整,对成藏有利;三是阿尔金山山前带优质基岩储集层分布影响了基岩气藏的局部富集,其分布受基岩岩性、风化淋滤强度等多因素控制;四是受多期构造运动控制,阿尔金山山前带断裂形成期次、活动性各有不同,起着控制基岩圈闭形成和油气差异成藏的重要作用。烃源岩分布差异、储集层发育差异、构造格局差异和断层活动性差异等多重因素共同控制了阿尔金山山前带基岩气藏的差异富集。

Differentiated Hydrocarbon Enrichment Factors of Bedrock Gas Reservoir in Piedmont Belt of Altun Mountain,Qaidam Basin

The bedrock gas reservoir whose formation is closely related to structural uplift and fault activity is mainly distributed in the piedmont belt of the basin margin and has the characteristics of differentiated hydrocarbon accumulation. Based on the systematic teasing of the main reservoir-forming factors of the bedrock reservoir in the piedmont belt of the Altun Mountain in Qaidam basin and combined with the exploration status worldwide, the paper summarizes the differentiated hydrocarbon accumulation in the bedrock reservoir. The study results show that there are four main factors controlling the formation of the bedrock reservoir in the piedmont area of Altun Mountain: 1.Several local hydrocarbon generating centers in Jurassic strata control the distribution and abundance of the bedrock gas reservoir in the piedmont zone. 2.There are three tectonic steps including uplift belt, slope belt and depression area in the piedmont belt, and the bedrock traps in the slope belt near hydrocarbon generating center are featured with the priority of oil and gas charging and good preservation, which are favorable for reservoir forming. 3.The distribution of high-quality bedrock reservoir in the piedmont belt which is controlled by multiple factors such as lithology of bedrock and intensity of weathering and leaching affects the local enrichment of the bedrock gas reservoir. 4.As a result of multistage tectonic activities, the formation period and activity intensity of the faults in the piedmont belt are different, which control the bedrock trap formation and differentiated hydrocarbon accumulation. It is concluded that the differences in source rock distribution, reservoir development, structural framework and fault activity jointly contribute to the differentiated hydrocarbon accumulation in the bedrock reservoir in the piedmont belt of Altun Mountain.