柴达木盆地西南区油气充注与青藏高原隆升耦合关系的包裹体证据

准确厘定柴达木盆地内含油气储层中烃类充注历史对于全面认识青藏高原隆升构造活动影响盆地内油气的成藏和分布均具有重要意义。本文详尽地调查了柴西南地区新生界主力含油层位的流体包裹体显微测温数据及所对应的烃类充注期次及时间,全面厘清了油气充注期次与高原隆升强活动期之间的耦合关系。研究结果表明,研究区油气藏普遍存在至少2期次的油气充注,通常发生在青藏高原隆升强活动期C、D和E期(中新世以后),几乎所有的油气藏均在强活动E期发生过规模化的油气聚集,说明青藏高原隆升运动末期的构造活动是研究区油气成藏和分布的关键影响因素。由于“多期成藏、晚期富集”的油气成藏特征,早期充注的石油可能改变砂岩储层的天然亲水性,有利于晚期油气的运移和聚集,在一定程度上弥补储层在继续埋藏过程中的物性损失,预示着深层存在油气勘探潜力的可能性。

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To determing the accurate charging history of hydrocarbon in the sandstone reservoirs of Qaidam Basin is significantly important to comprehend the effects of Tibetan Plateau uplifting on the migration and accumulation of oil and gas in this basin. The microthermometry data of brine inclusions that related to hydrocarbon movements and the coreesponding stages and ages of hydrocarbon chargings are investigated to clarify the coupling relationship between the uplifting activities of Tibetan Plateau and hydrocarbon accumulations in the Cenozoic of southwestern Qaidam Basin. Two stages of hydrocarbon chargings that occurred in the active periods C, D and E (all after Miocene) of the plateau and the large-scale hydrocarbon accumulation that occurred in the active Period E for almost all of oil and gas reservoirs are proposed. It is suggested that the tectonic activities during the late uplift period is the key factor influencing the migration and distribution of oil and gas, and the enrichment of oil and gas depends on the late adjustment of hydrocarbon. The wettability alteration resulted from the early hydrocarbon chargings is regarded as an offset to the possible loss of reservoir quality during the successive burial and to be beneficial for the late oil and gas to migrate and accumulate. A potential of hydrocarbon exploration is proposed in the deeper-buried sandstones of this basin.