柴达木盆地西部埋藏史分析与油气关系类型

An Analysis of the Burial History of Western Qaidam Basin in Relation to Oil-Gas Accumulation

地层埋藏史研究是借助计算机恢复地层古厚度,动态的再现盆地的沉积发育过程,同时也是含油气系统研究的核心内容,是研究油气的生、运、聚及成藏过程的基础和关键。本文在区域概况分析的基础上,应用EASY%Ro方法定量计算了柴达木盆地西部31口重点探井的剥蚀量,并应用实例详细论证了该方法恢复的剥蚀量是合理可靠的,然后应用回剥技术恢复原始地层厚度,做出了单井埋藏史图。并划分出了连续沉积型、中期剥蚀型和晚期强烈剥蚀型3种埋藏史类型。埋藏史与油气的关系密切:未遭受强烈抬升、剥蚀影响的地区能够较好的保存原生油气藏;而后期的强烈剥蚀使得早期的原生油气藏遭到破坏,同时又导致了浅层次生油气藏的形成。这对正确认识该地区沉积沉降演化历史和成藏机制,指导油气勘探具有重要作用。

Burial history analysis, by which the depositional process can be reproduced dynamically on computer according to the restored fossil strata thickness, is the core of petroleum system research and also serves as the basis and key in the study of hydrocarbon generation, migration and accumulation. On the basis of a regional geological background analysis, the total thickness of the eroded strata was calculated quantitatively by EASY% Ro method. The thickness of the eroded strata was proved reasonable and reliable by examples, and the original thickness of formations was restored by the backstripped technique. Maps for the burial history of single wells were drawn and the burial history was divided into three types, namely non-erosion （continuous sedimentation）, middle erosion and late erosion. There exists close relationship between burial history and oil-gas accumulation. The primary oil-gas reservoirs might be preserved in areas not affected by strong uplift and erosion. Nevertheless, late strong erosion could destroy primary oil-gas reservoirs and lead to the formation of secondary oil-gas reservoirs in shallow layers. The results of the study can play an important role in recognizing sedimentary evolution history and guiding oil-gas exploration work in western Qaidam.