油田注水开采地震监测理论研究

Theoretical study of the seismic monitoring of oilfield waterflood recovery

在高孔隙度低粘度（小于100mP·s）油田开发中，注水开采是目前世界上应用最为普遍的改善采收率的方法。本文根据Gassman方程和岩石密度平均方程着重研究了注水强化开采过程中，由于水置换砂岩储层中不同油气比原油所引起的纵横波速度和密度的变化规律，并通过三种地质模型的试算对水置换石油所引起的界面反射系数变化规律进行了分析和研究。研究结果表明，由于水置换石油所引起的砂岩纵横波速度和密度以及界面反射系数的变化是十分显著的。对含中、高油气比原油的砂岩储层来说，其反射系数相对变化率约在30％左右，有时甚至可高达40％或50％以上。而对含低油气比原油的砂岩储层，其反射系数的相对变化率也至少可达到17％以上。上述研究为地震注水监测提供了重要的理论依据。

In the development of high porosity and low viscosity (less than 100mPa·s) oilfield, the waterfloodrecovery is the most widely used method in the world at present to improve the recovery ratio. In the paper, accorcing to the Gassman equation and the rock density average equation, we emphatically researchon the variation law of P- and S-wave velocity and density due to the replacement of oil with differnt oilgas ratio in sandstone reservir by water in waterflood enhanced recovery. The trial computation forthree geological models are performed to analyze the variation of interface reflection coefficients caused bythe replacement of oil by water. The research results show that the variation of sandstone P-ant S-wavevelocity, density, and interface reflection coefficients caused by water replacing oil is very obvious. Forthe sandstone reservoir bearing oil with high or middle oil-gas ratio, the relative change rate of reflectioncoefficients is about 30%, aometimes more than 40% or 50%. And it is at least more than 17% for thesandstone reservoir bearing oil with low oil-gas ratio. The above researches give an important theoreticalbasis for the seismic monitoring of waterflood recovery.