砂岩油藏地震数据流体替换

Fluid substitution based on seismic data of sand reservoirs

流体替换常用于计算油藏流体变化前后岩石弹性参数变化,是进行地震油藏描述与监测研究的关键步骤。流体替换需要孔隙度、岩石基质、流体属性和泥质含量等数据信息,因此目前往往只能在有测井数据的油藏部分进行流体替换,并通过地震数值模拟获取流体变化前后地震响应,从而进行地震属性分析与优化。为了扩大流体替换应用范围,提出利用地震资料直接进行流体替换。在确定油藏流体类型与岩石物理模型基础上,建立油藏地质模型,模拟油藏流体变化前后地震反射振幅峰值关系,并分析储层参数(包括孔隙度、储层厚度和泥质含量等)变化时该振幅关系变化特征。采用曲线拟合方式对该振幅峰值关系进行计算,得到可直接应用于地震数据的流体替换线性拟合方程,从而进行实际地震数据流体替换。基于胶结砂岩油藏岩石物理模型的模拟分析与实际资料应用试验,证明了基于地震数据流体替换的可行性。

Fluid substitution is commonly used to compute elastic property parameters of rocks before and after the variation of reser- voir fluids, which is a key procedure in seismic reservoir characterization and monitoring. However, fluid substitution requires the information on parameters of rock porosity and matrix, fluid properties, clay content, etc. Therefore, at present fluid substitution can be only conducted on the part of a reservoir that has available log data, and the dynamic seismic response of fluid variations is ob- tained through seismic numerical simulation during seismic attribute analysis and optimization. In order to expand the application of fluid substitution, we proposed to directly conduct fluid substitution by utilizing seismic data, in which a geologic model of oil reser- voirs was established to simulate the amplitude peak value correlation of seismic reflection between wet and gas reservoirs according to the determination of reservoir fluid types and petrophysical models, and to characterize variations in the amplitude correlation dynamically with the change of reservoir parameters, including porosity, thickness and clay content. The correlation was calcu- lated by means of curve fitting to obtain a linear equation of fluid substitution capable of the direct application to seismic data, a- chieving the fluid substitution of in-situ seismic date. Both the simulation analysis based on the petrophysical model of cemented- sand reservoirs and the application experiment of in situ seismic data have proved the feasibility of directly conducting fluid substi- tution based on seismic data.