深层-古老海相层系温压场与油气成藏

Temperature-Pressure Field and Hydrocarbon Accumulation in Deep-Ancient Marine Strata

深层海相碳酸盐岩层系尚处于勘探初期,对于海相盆地深层温压场的演化特征及主控因素认识还不够清晰.本文总结了适用于深层海相层系的温压场研究方法,并以川中古隆起震旦系气藏和塔中隆起奥陶系凝析气藏为例,展示温压场恢复的结果.川中古隆起震旦系灯影组的温度演化经历了升温-降温-快速升温-快速降温的过程,主要受大地热流与沉积埋藏史的控制;而塔中隆起奥陶系则经历了持续缓慢增温的过程,现今为最高温度.川中震旦系和塔中奥陶系现今地层压力都表现为常压,但前者经历了常压-弱超压-强超压-卸压的演化过程,而塔中隆起奥陶系在3次主要的油气成藏期没有明显的超压.对温压场的系统研究,有助于解释塔中隆起和川中古隆起现今油气相态的差异,还可以为碳酸盐岩储层高温高压模拟实验提供参数,为海相大气田进一步勘探提供理论指导.

Deep marine carbonate strata are still in the early stage of exploration,and the evolution characteristics and main controlling factors of deep temperature and pressure field in marine basin are not clearly understanded. In this paper,the evolution of temperature and pressure of the Sinian gas reservoir in the central paleo-uplift of Sichuan Basin and the Ordovician condensate gas reservoir in the central uplift of Tarim Basin are reconstructed,on the basis of our summaries of suitable methods for deep marine reservoirs,in combination with our research findings and relevant literatures,the present geothermal gradient and heat flow in both the Sichuan and Tarim basins are lower. The Sinian Dengying Formation experienced the changes of warming-cooling-fast warming-fast cooling,which were mainly controlled by the heat flow and burial history. But the Ordovician in the central Tarim Basin underwent a sustained and slow warming process,and the present temperature is the highest during the geological time. The present-day pressures in both two reservoirs are in normal state. The Dengying Formation experienced the normal pressure,weak-overpressure,strong overpressure and pressure relief;but there were no obvious overpressures during the three major hydrocarbon accumulation periods in the Ordovician. The systematic research on temperature and pressure is not only very favorable for gas phase interpretations in these two gas reservoirs,but also provide modeling parameters for high temperature-high pressure experiment of carbonate rocks,improve the accumulation theory of deep marine strata,and support the further hydrocarbon exploration in deep marine gas field.