利用Sigmoid函数表征超低渗透储层的非达西渗流特征

Characterization of the non-Darcy seepage flow in ultra-low permeability reservoir based on Sigmoid function

达西渗流产水率模型已难以准确描述超低渗透储层的产液性能,为了准确表征超低渗透储层的产液能力,必须基于非达西渗流特征建立高精度产水率模型.神经元非线性函数Sigmoid的突变性质能较好地描述非达西渗流特征,并可以通过改变系数来控制其突变时间和幅度,因此,引入该函数来构建超低渗透储层的产水率模型.在超低渗透储层,压裂改造措施破坏了油藏状态下含水饱和度与产水率之间的关系;计算方法和实验分析所携带的误差造成计算含水饱和度与油藏状态下含水饱和度之间存在数值差异.分类弥补这一差异之后,利用Sigmoid函数建立的产水率模型计算97口井的产水率,与实际压裂试油的产液数据进行对比分析,相关系数为0.900 4,满足研究区实际勘探开发生产需求.

The reservoir water-cut model based on Darcy flow cannot accurately describe the water-producing performance of ultra-low permeability reservoirs.The reservoir water-cut model based on non-Darcy flow must be established for ultra-low permeability reservoirs.The sudden-change nature of Sigmoid function can well describe the seepage flow characteristics of the non-Darcy flow,and the sudden change time and the amplitude of it can be controlled by changing the coefficients of the function.The model for calculating the water-producing rate of ultra-low permeability reservoirs based on Sigmoid function is established according to the fitting of core analysis water-producing rate data,which is a relation formula between the water-producing rate and water saturation.But for fractured ultra-low permeability reservoirs,since the fracturing measures changes the relationship between the water-producing rate and the water saturation and there is the difference between the water saturation calculated by Archie formula and the actual reservoir water saturation,the water-producing rate-water saturation relation based on Sigmoid function is not uniform with the water-producing rate-water saturation relation based on core analysis.After the water saturation calculated by Archie formula is corrected,there is good consistency between both.The water-producing rate of 97 wells is calculated using corrected water saturation according to the established model,and compared with the actual water-producing data,their correlation coefficient is 0.900 4,which can meet the practical need of exploration and production.