基于流管模型的裂缝性低渗透油藏井间示踪剂解释模型

裂缝性低渗透油藏的示踪剂产出曲线与常规储层不同,存在多个峰值,需要建立针对裂缝性油藏的示踪剂解释模型。将该类储层中的裂缝系统考虑为多条裂缝条带,并将裂缝条带等效为流管束,建立示踪剂在井间流动的物理模型。基于一维对流扩散方程,沿着流管建立了示踪剂浓度分布数学模型,在生产层将各裂缝条带的浓度叠加后,得到示踪剂浓度产出表达式。敏感性分析表明,随着裂缝条带等效流管数增加,浓度产出曲线峰值下降;随着流管长度增加,生产井见剂时间增长,且峰值浓度降低;随着渗透率和注采压差增大,生产井见剂时间减小,浓度产出曲线带宽增加。现场应用表明,该模型的解释结果与数值模拟解释结果相近,验证了模型的合理性。

Interpretation Model for Inter-well Tracer Tests in Fractured Low-permeability Reservoirs Based on Stream-tube Model

Due to the strong heterogeneity,the tracer production curve of fractured reservoirs low-permeability has multiple peaks,which is different from that of conventional reservoir.So,it cannot accurately describe the information of fractures.Therefore,it is urgently to establish a tracer interpretation model for fractured reservoirs.In this paper,the fracture system of reservoir is considered to be composed of many fracture belts,and the fracture belt is equivalent to the stream tube.Based on above assumptions,the physical model of inter-well tracer flow is established.Moreover,a mathematical model of the tracer concentration distribution along the stream tube is built according to the one-dimensional convection-diffusion equation.After the concentration of each fracture belt is superimposed in the production layer, the tracer concentration production expression is obtained.Sensitivity analysis show s that as the number of equivalent stream tubes increases, the peak value of the concentration production curve decreases;as the length of flow tubes increases,the tracer breakthrough time increases,and the peak concentration decreases;as the permeability and pressure difference between injection and production well increase,the breakthrough time decreases,and the bandwidth of concentration production curve increases.T he field application show s that the results of this model are close to the numerical simulation interpretation result,which validates the rationality of the model.