缝洞型油藏离散数值试井解释方法研究

Study on the Interpretation Method for Discrete Numerical Well Test of Fracture-Cave Type Reservoir

塔河油田奥陶系碳酸盐岩油藏主要是裂缝和溶洞组成的缝洞型储层,非均质性极强,基质系统不具有储渗能力,地层流体以管流或管流)渗流耦合流动为主。传统试井解释方法基于多重连续介质模型和解析渗流理论,难以对储层特征和流体流动规律正确描述。离散数值试井解释方法通过连续性特征分析,把溶洞和裂缝视为离散介质进行处理,把缝洞型储层等效为粗细溶洞相间的组合模式,并对粗细溶洞中的流体流动进行管流公式和等效渗流公式描述,建立8种试井地质模型,对径向流、线性流和储罐流分别进行有限差数值方法求解,绘制典型曲线并分析各流动阶段压力特征。通过T762井实例应用分析,其解释结果能更好地描述缝洞型油藏特征并指导开发。

Carbonate oil reservoirs at the Tahe oilfield can be categorized as Ordovician,whose reservoirs belong to the fracture-cave type.That is,the reservoirs are mainly composed of fracture and cave,and they showvery strong heterogeneity.Besides,the matrix is incapable of carrying out storage and flow,and the formation fluid flowismainly conduitflowor coupled flowof conduit-seepage.Traditional pressure transient analysis methods,which are usually based on the multiple continuum model and analytic seepage theory,have difficulty in accurately describing the characteristics of reservoirs and the rule of flow.By analyzing the continuity characteristics,the discrete numerical well testmethod considers cave and fracture as discrete medium,and the fracture-cave type reservoir as the combination of couplet cave that appear alternatively.On that basis,the discrete numerical well test method describes the flow in couplet cave by using conduit flow and the equivalent seepage formulas, and constructs eight types of models forwell test analysis.Thismethod achieves the solutions for radial flow,linearflow and tank flowby using the finite difference method,draws the typical curves of differentflow regime,and analyzes the characteristics of the pressures.Filed applications in T762 show that the resultfor describing the characteristics of fracture-cave reservoir is better than that achieved by using the traditional methods.The results can be used to guide the development of fracture-cave reservoirs.