柴北缘尕丘凹陷大煤沟组烃源岩特征及有利勘探目标分析

Analysis of the source rock characteristics of Dameigou Formation and the favorable exploration target in Gaqiu Sag of the northern margin of Qaidam Basin

为明确柴达木盆地北缘尕丘凹陷烃源岩生烃潜力和有效性,选取尕丘凹陷及周边地区典型烃源岩和原油样品,进行岩石热解峰温、总有机碳质量分数、干酪根镜检类型指数和饱和烃色谱—质谱等分析测试,开展烃源岩地球化学评价和油源对比,分析烃源岩展布和埋藏热演化史、油气源、运聚及保存等条件,明确有利勘探目标区。结果表明:尕丘凹陷发育有机质丰度为优质等级、有机质类型以Ⅱ1型为主的烃源岩;烃源岩总面积为750 km^(2),厚度为50~400 m;尕丘凹陷北部洼陷主体烃源岩埋藏经历两次抬升,目前处于低成熟—成熟阶段,以生油为主,烃源岩生成的原油在马北、绿梁山、圆丘等构造和地区聚集成藏;北部洼陷近洼地区发育的背斜、断背斜等构造圈闭为研究区有利勘探目标。该结果为尕丘凹陷进一步勘探提供依据。

In order to clarify the hydrocarbon potential and effectiveness of the source rock in the Gaqiu Sag,northern margin of Qaidam,typical source rocks and crude oil samples from this depression and its surrounding areas are selected for the rock-eval pyrolysis,the total organic carbon,the analysis of kerogen macerals and saturated hydrocarbons GC-MS,are used to evaluate geochemical characteristics of the source rock and oil-source correlation.Through analysis of the source rock distribution,the thermal evolution,the oil and gas source,the accumulation,the preservation and other conditions,the favorable exploration targets are indicated.The results show that the source rocks are high quality organic matter abundance and the organic matter types of the source rocks are primarily Ⅱ_(1) in Gaqiu Sag.The total area of source rock is about 750 km^(2)with a thickness of 50-400 m.The main source rock buried in the northern depression of Gaqiu Sag has been uplifted twice,and is in the low-mature stage now,mainly oil generation.The oil generated by the source rock in Gaqiu Sag have accumulated in Mabei,Lyuliang Mountain,Yuanqiu Areas.The traps of anticlines and fault block anticlines near the north sub-depression are favorable exploration targets in this area.The research results provide the basis for the the further exploration.