基于等级加权法的油田注水水质优选方法

Optimum Selection Method of Oilfield Water Injection Quality Based on Grade Weighting Method

目前油田注水水质选择依据SY/T 5329—2012标准,以注入层平均空气渗透率作为唯一评价指标,缺乏必要理论支撑与数据支持。综合考虑渗流物性、孔隙结构、胶结物性质以及地层水性质4个指标,以注水水质优选为目标,采用等级加权法对影响4个指标的各因素进行赋值以及权重的分配,建立油田注水水质优选方法,并利用Matlab软件编写计算程序,对X和M油田注水水质进行了优选。结果表明:X油田注水水质应选择SY/T 5329—2012标准中注入层平均空气渗透率为(0. 05～0. 5)μm2对应的注水水质控制指标,优选结果与标准一致,但评价结果更全面地考虑了各因素的影响; M油田注水水质应选择SY/T 5329—2012标准中注入层平均空气渗透率为(0. 05～0. 5)μm2对应的注水水质控制指标,优选结果严格于行业标准。优选方法可以指导注水水质的合理选择,减少后期酸化解堵的费用,提高油田的开发效益。

At present,the selection of water injection quality is based on standard SY/T 5329-2012,and the average air permeability of water injection reservoir isonly evaluation index,which lacks theoretical support and data support. In this paper,considering four indexes of reservoir physical property,pore structure,cement property and formation water property,taking the quality of injected water as optimization objective,value assignment and weight allocation of factors affecting the four indicators are finished by using hierarchical weighting method,and an oilfield injection water quality optimization method is established. Corresponding calculation program is compiled by using MATLAB software. The quality of injected water for X and M oilfields is optimized using this method. The results show that,the injected water of X oilfield should have the water quality control indexes corresponding to the injection water for average air permeability 0. 05 ~ 0. 50 μm2 of injecting layer in SY/T 5329-2012 standard. The optimization result is consistent with that of optimization based solely on average air permeability of injection layer,but it considers the influence of various factors more comprehensively.The injected water of M oilfield should also have the water quality control indexes corresponding to the injection water for average air permeability 0. 05 ~ 0. 50 μm2 of injection layer in SY/T 5329-2012 standard,and the result of optimization is stricter than that of optimization based solely on average air permeability of injected layer. This water quality optimization method can be used for guiding the rational selection of injected water,reduce the cost of acidizing plugging removal in the later stage,and improve the development efficiency of oilfields.