多层复合油藏试井解释模型建立

Foundation of well test interpretation model for composite reservoirs with multi-layers

油藏开发过程中,多层非均质油藏呈现与单层均质油藏的不同特性,层间及平面物性差异会对产量的贡献及压力衰竭程度造成影响。本文从渗流力学基本理论出发,建立了多层复合油藏试井解释模型,通过Laplace变换和Stehfest数值反演对模型进行求解,获得典型试井分析样版曲线,对反映储层特征的参数敏感性进行分析。结果表明,无层间窜流的多层复合渗流模型表现出压力导数曲线存在反映复合物性变化的"台阶"型;每个层的复合变化不同会引起压力导数出现多个"台阶"。试井解释时,应区别储层物性变化或不渗透边界造成的压力导数曲线上翘。该模型可以对多层合采且储层平面存在变化的复合油藏进行评价,获取多层合采复合油藏各分层渗透率、表皮系数、地层压力、边界等参数信息,为该类储层描述和开发规律提供指导及理论依据。

During the reservoir development process,the multi-layer heterogeneous reservoirs exhibit different characteristics from the single-layer homogeneous reservoirs.This difference was mainly reflected in the influence of the difference in interlayer and plane physical properties on the yield and the degree of stress failure.Based on the basic theory of seepage mechanics,a well test interpretation model for multi-layer composite reservoirs was established.The Laplace transform and Stehfest numerical inversion were used to solve this model,and then the pattern curve of typical well test analysis can be obtained to analyze the sensitivity of the parameters which reflect the reservoir characteristics.The results showed that the multi-layer composite seepage model without interlayer turbulence can reflect the change of composite properties.The main feature was that the pressure derivative curve would have a "step" shape,and the difference of the composite changes of each layer would cause the pressure derivative to appear multiple "steps".During the interpretation of well test,the upwarping of the pressure derivative curve caused by the reservoir physical property change or the impermeable boundary should be distinguished.The model can evaluate the composite reservoirs with commingling production and changes in reservoir plane,and obtain the parameters such as permeability,skin factor,formation pressure and boundary of each layer of composite reservoir commingling production,which can provide guidance and theoretical basis for reservoir description and development rules.