砂岩储层AVO特征影响因素的不确定性研究

传统的地震AVO正演研究多采用参数固定的岩石物理模型,而实际地层属性参数在勘探范围内具有不确定性.本研究以目标地层岩芯样品的实验室测试数据为基础,通过样品孔隙度和干燥状态下纵、横波阻抗的高度线性关系对岩石物理模型进行了简化,并结合实验测量和测井解释建立了主要模型参数的概率密度函数.采用Monte-Carlo随机正演和G...

The uncertainty analysis of the key factors that affect the AVO attributes in sandstone reservoir

Traditional seismic AVO forward study normally uses constant parameters to construct rock physics model, but these parameters in real formations have uncertainties across exploration area. Using laboratory measurements of cores from target formation, the rock physics model was simplified with relationships of reservoir sandstone porosities and P- and S-wave impedances in dry condition. To study influences of model parameter uncertainties, the probability density functions of key model parameters were introduced based on core measurement and well logging analysis. Using Monte-Carlo method and Gassmann fluid replacement technique, the AVO responses of models were obtained for saturation fluids as brine, oil and gas. The comparative analysis indicates that the velocity uncertainty of covering mud is the primary factor affecting the fluid cluster's distribution and deviation from water background trend on AVO intercept-gradient crossplots, while the porosity uncertainty of sand is also significantly affecting but less than covering mud. Thus, the correct interpretation of AVO anomalies for real seismic data requires forward simulation on probabilistic rock physics model to find out the most likely reservoir and fluid characters.