储层条件下气-水和油-水互驱地震岩石物理实验研究

Seismic rock physical experiment on the porous fluid replacement at reservoir conditions

针对影响岩石波速的主要因素——不同孔隙流体,展开了储层条件下气-水和油-水互驱地震岩石物理实验研究。在模拟储层温度、压力条件下,对取自南海的砂岩岩样进行了不同含水饱和度的气-水和油-水互驱波速测量实验,获得了不同状态下的纵、横波波速,得到了不同气-水、油-水条件下的弹性参数变化规律。实验表明:①在气-水驱替过程中,纵波速度vP随着含水饱和度Sw的增大呈缓慢增长趋势,当含水饱和度达到80%后,vP增长较快;②在水驱油过程中,vP随着含油饱和度的增加而减小,且实验波速值与经典的Biot-Gassmann理论值两者吻合较好;③气-水驱替过程中,vP/vS对不同含水饱和度的孔隙流体反映较为灵敏,通过泊松比σ与体积模量K交会分析可以较好地分离饱气与饱水岩样;④水驱油过程中,泊松比σ、拉梅常数λ和流体敏感因子F等参数对不同含水饱和度(含油饱和度)的孔隙流体反映较为敏感,利用λ-F交会图可以区分饱水和饱油岩样。这些实验结果为利用叠前地震属性进行油气检测提供了有利依据。

Different porous fluid is the main factor impacting the acoustic velocity of rock.In terms of this recognition,we carried out seismic rock physical experiment at reservoir conditions including gas-water and oil-water replacement.The wave velocity experiment of sand rock samples taken from the South China Sea in different gas-water and oil-water systems under simulated temperature and pressure conditions is studied.Some parameters were obtained,including vP,vS and the variation law of the elastic parameters in different gaswater and oil-water conditions.The results indicate:①In the gaswater replacement experiment,vP grows slowly along with the Sw increases.When the Sw >80%,vP grows faster;②In the oil-water replacement experiment,vP decreases with the So increases,and the experimental acoustic velocity coincides with that of classic BiotGassmann theory;③In the gas-water replacement experiment,the vP/vS reflects more sensitively to different content of water saturation,both the gas-saturated samples and water-saturated samples would be separated by the crossplot of K-σ;④In the oil-water replacement experiment,some parameters includingσ,λand F are more sensitively to the different content of water saturation(oil saturation),both the oil-saturated samples and water-saturated samples would be separated by the crossplot ofλ-F.These results can be used to detect oil and gas in prestack seismic attribute analysis.