胜利油田高89区块CO_2驱油与地质封存过程中横波速度预测方法研究（英文）

Shear wave velocity prediction during CO_2-EOR and sequestration in the Gao89 well block of the Shengli Oilfield

CO_2驱油与地质封存过程中,预测储层横波速度曲线及横波速度随注入压力或产出压力的变化,是解释四维地震监测数据的关键。但是在实际油田中,横波测井资料较少。尤其是在CO_2地质封存的四维地震监测中,CO_2注入之后会把井关闭,而无法进行测井。但后续还要进行地震监测,因此需要预测CO_2注入之后的纵横波速度。CO_2注入之后,储层的压力和饱和度都会发生变化,弹性参数也发生了变化。本文以胜利油田高89区块为例,利用Hertz-Mindlin公式和Gassmann方程结合,提出了预测横波速度,以及不同孔隙度储层随压力变化的横波速度预测方法。由于Hertz-Mindlin公式中的配位数为未知量,本文还提出了Hertz-Mindlin公式中配位数的计算方法。利用本文提出的方法分别制作了不同CO_2注入阶段的储层纵横波速度变化曲线,然后根据这些预测速度曲线制作四维人工合成地震记录,将四维人工合成地震记录与实际四维地震数据进行对比,其相关性高。

Shear-wave velocity is a key parameter for calibrating monitoring time-lapse 4D seismic data during CO2-EOR （Enhanced Oil Recovery） and CO2 sequestration. However, actual S-wave velocity data are lacking, especially in 4D data for CO2 sequestration because wells are closed after the CO2 injection and seismic monitoring is continued but no well log data are acquired. When CO2 is injected into a reservoir, the pressure and saturation of the reservoirs change as well as the elastic parameters of the reservoir rocks. We propose a method to predict the S-wave velocity in reservoirs at different pressures and porosities based on the Hertz-Mindlin and Gassmann equations. Because the coordination number is unknown in the Hertz Mindlin equation, we propose a new method to predict it. Thus, we use data at different CO2 injection stages in the Gao89 well block, Shengli Oilfield. First, the sand and mud beds are separated based on the structural characteristics of the thin sand beds and then the S-wave velocity as a function of reservoir pressure and porosity is calculated. Finally, synthetic seismic seismograms are generated based on the predicted P- and S-wave velocities at different stages of CO2 injection.