重力测井用于注CO_2油藏监测的理论分析

Theoretical Analysis of the Application of Gravity Logging to the Monitoring of CO 2 Injected Reservoir.

云美厚，蔺景龙，于舒杰．重力测井用于注ＣＯ２油藏监测的理论分析．测井技术，１９９８，２２（４）：２４１～２４４在３次采油过程中，注采已为广泛应用，但所面临的问题是如何确定油层中注入流体的波及范围、流体前缘位置及推进速度等。利用地震方法进行注采由于受地震资料分辨率的限制，只适用于浅层，而其它测井方法由于探测范围限制，揭示井间注采动态又显不足。重力测井具有探测范围大、受井径变化影响小、重复观测周期短、不受目的层埋深限制等优点。通过正演模拟分析表明，重力测井方法不仅可监测ＣＯ２前缘空间位置的变化，而且可以判定ＣＯ２前缘的推进方向，进一步可用不同时间不同观测井的监测结果确定ＣＯ２波及面积以及推进速度。

Water and CO 2 injection is widely used in tertiary recovery. The problem is how to determine the swept volume, the position of the injected fluid front and the frontal advance rate. The seismic method is only adaptable to shallow zone due to its limited resolution and logging methods other than gravity log are not good enough to reveal the injection performance between wells because of their limited investigation range. Gravity log has such advantages as wide investigation range, small effect of caliper variation, short repeated observation cycle, no limit for depth of the interested zone. Forward modelling result shows that gravity log is capable of monitoring not only the positional variation of the CO 2 injection front but also the direction of the CO 2 frontal movement. Furthermore, the swept volume and advance rate of the CO 2 injection can be determined by the monitoring results from different observation wells at different time.