塔里木盆地海相油气成藏年代与成藏特征

GEOCHRONOLOGY AND CHARACTERISTICS OF MARINE HYDROCARBON ACCUMULATION IN THE TARIM BASIN

塔里木盆地海相油气具有多期成藏、晚期调整的特点 ,早期形成的油气藏普遍受到后期不同程度的调整改造 ,以晚喜马拉雅期调整改造最为强烈。目前发现的古生界海相油藏主要为晚海西期形成的原生油藏 ,而中生界海相油藏以及部分古生界海相油藏则主要为燕山期特别是晚喜马拉雅期古油藏发生调整而形成的次生油藏。造成塔里木盆地海相油气藏普遍出现晚期调整的原因 ,一是中_ 新生代特别是晚喜马拉雅期强烈的构造变动和断裂活动 ,二是晚喜马拉雅期强烈的气侵作用 ,克拉通区圈闭幅度普遍较低也是其易发生调整的一个重要原因。因此 ,构造相对稳定的继承性古隆起和古斜坡区 ,是塔里木盆地寻找大_ 中型海相原生油藏的主要地区 ,其中以塔中隆起及其北斜坡、轮南凸起及其南斜坡和西斜坡。

A study on geochronology and filling history of marine hydrocarbon reservoirs in the Tarim basin revealed that hydrocarbon migration and accumulation there experienced an extremely complicated history of multiple migration accumulation and later adjustment. The earlier accumulations were more or less reworked by later tectonic orogenies which were very strong and frequent particularly during the Neogene to Quaternary (i.e. Late Himalayan). The primary reservoirs were formed during 3 major periods, namely, Late Caletonian to Early Hercinian, Late Hercynian and Himalayan, whereas the secondary generated reservoirs were mostly formed in the Late Hymalayan through adjustment of earlier formed primary accumulations. Many Paleozoic oil fields were mainly primary ones formed in Permian; while most of the Mesozoic as well as some Paleozoic oil reservoirs were secondary ones, as a result of adjustment of early primary ones in the Late Himalayan. The reasons for adjustment of marine hydrocarbon accumulations commonly occurring might be strong orogeny and faulting, and intrusion of high over matured natural gas in the Late Himalayan; in addtion, the less altitude of traps was easier for widespread adjustment of earlier formed petroleum reservoirs in the cratonic area. Therefore, the relatively stable inherited paleo uplifts and their slopes were major target region for mid large marine primary oil fields, in which the Central Tarim Uplift and its north slope, south and west slopes of the Lunnan Uplift, the Maigaiti slope and the recently discovered Hadexun Uplift should be most favorable.