一种反演水淹层混合水电阻率的新方法

注水开发油田储层水淹后电性特征变化复杂，混合水（注入水和原生地层水的混合液）矿化度不仅受注入水和原生地层水矿化度的控制，还受水淹程度等因素影响，造成混合水电阻率和岩电参数的动态变化，为水淹层的识别和剩余油饱和度的评价带来较大困难。以渤海S油田为例，利用图论多分辨率聚类算法对测井相进行划分，建立了测井相约束下的束缚水饱和度评价模型；根据岩电实验数据讨论了岩电参数随地层水矿化度变化的规律，提出水淹层中胶结指数和饱和度指数与混合水矿化度的函数关系。在此基础上，通过迭代反演得到水淹层剩余油饱和度和混合水电阻率，实现了水淹层的定量评价。研究结果表明：（1）利用图论多分辨率聚类算法可以对测井相进行有效划分，基于测井相约束的束缚水饱和度模型精度高于未分相的结果；（2）水淹层储层胶结指数和饱和度指数随混合水矿化度增大而增大，二者具有明显的幂函数关系；（3）该方法划分水淹层结果与S油田产出剖面测井测量结果吻合率为92.3%，明显提高了水淹层的评价精度。

A New Method for Inversing Mixed Water Resistivity in Water-flooded Zone

The changes of electrical properties of water-flooded reservoirs are complex.Salinity of mixed water is influenced not only by the salinity of injected water and primary formation water,but also by the degree of flooding,which will lead to dynamic changes of resistivity of mixed water and electrical properties of rock and will bring great difficulty to the identification of water-flooded zones and the evaluation of remaining oil saturation.S oilfield in Bohai Area is taken as an example to illustrate how to solve the problems mentioned above.First of all,method of logging facies classification is proposed based on the theory of Multi-Resolution Graph-based Clustering and models of bound water saturation is established in different logging facies.Then the variation law of rock electricity parameters with the change of formation water salinity is analyzed on the basis of rock electricity experimental data,and the exponential relationship between m,n and salinity of mixed water in water-flooded zone is raised for the very first time.Finally residual oil saturation and resistivity of mixed water in water-flooded zone is calculated and quantitative evaluation of water-flooded Zone is realised.The main understandings are as follows:(1)logging facies can be effectively classified based on the theory of Multi-Resolution Graph-based Clustering and there is a much higher precise of bound water saturation by the method than the conventional model without logging facies;(2)with the increase of the salinity of mixed water,rock-electro parameters increase obviously in the low salinity area and the growth rate slows down in the high salinity area;(3)the quantitative interpretation results of water-flooded zone are in good agreement with actual production data and fluid yield profile logging results and the total coincidence rate is up to 92.3%,which shows that the evaluation accuracy of water-flooded zone is improved obviously.