油气水界面追溯法——研究烃类流体运聚成藏史的一种重要方法

HYDROCARBON-WATER CONTACT RETROSPECTION: AN EFFECTIVE METHOD IN TIMING HYDROCARBON FLUID ACCUMULATION

通过对塔里木盆地多个油气藏的油气水界面演化史与成藏期的综合分析 ,认为油气水界面追溯法是研究烃类流体运聚成藏期与成藏演化史的一种十分有效的方法。其确定成藏期、恢复成藏演化史的基本原理是 ,规则油气藏形成时其油气水界面通常为一水平的界面 ,以后因构造变动等影响 ,油气水界面可能发生变迁 ,直至构造稳定期其油气水界面又重新演变为水平的界面。因此 ,可以通过对油气藏油气水界面演变史的分析 ,研究油气藏的形成演化历史。具体做法是 ,首先编制大比例尺圈闭发育史剖面图 (或平面图 ) ,然后计算现今油气藏的油气水界面在各地质历史时期的古埋深 ,并标于相应时期的剖面图 (或平面图 )上 ,则现今油气水界面埋深最早形成水平直线或水平界面的时间 ,即是油气藏的形成时间。其后的油气水界面变迁则纪录了油气藏形成以后调整。

Based on the analyses of the forming time of many petroleum reservoirs in the Tarim basin, it can be concluded that hydrocarbon\|water contact retrospection of reservoirs is an effective method in timing the formation of petroleum accumulations. The basic principle of this method is that a regular reservoir is formed with a leveled oil or gas\|water contact,which may be altered by later tectonic movements or other geologic events and would not readjust to a leveled one until to a static tectonic period. Therefore, the hydrocarbon charging time can be estimated by tracing the earliest occurring time of the leveled contact. The timing of the studied reservoirs estimated by this method has been verified by other methods such as fluid inclusions and isotopic dating of illites in reservoirs. The specific method is as follows: first, compiling a large\|scaled map or profile of trap evolutionary history; then calculating the buried depth of the present oil\| or gas\|water contact in each geologic interval; finally, marking the paleo\|depth to the present oil\| or gas\|water contact on the trap evolution profile or map of corresponding interval and observing the earliest time of leveled hydrocarbon\|water contact, which is the forming time of the hydrocarbon reservoir. Later changes of the hydrocarbon\|water contact are a record of the history of adjustment and even destruction of the reservoir. Therefore, the hydrocarbon\|water contact retrospection can be used as an effective method in determining hydrocarbon filling time and studying the accumulation history of a petroleum reservoir.