低渗透油藏水平井注CO2井网优化与影响因素

Well Pattern Optimization and Influencing Factors for CO_2 Injection of Horizontal Wells in Low Permeability Reservoir

针对低渗透油藏直井井网CO_2驱油的不足,以大庆某低渗区块为例,建立反七点水平井井网CO_2驱油地质模型。在物性参数相态拟合的基础上,对反七点水平井和五点直井两种不同井网模式的开发效果进行了对比,对反七点水平井井网参数进行了优化,同时对储层非均质(渗透率、储层非均质性、裂缝的发育情况等)进行了影响因素分析。研究表明:利用水平井注CO_2可以适当地增大井距、排距,减少井的数量,降低钻井成本;在生产制度相同的情况下水平井井网的开发效果要比直井井网的开发效果好;在水平井井网中,采出程度随着油井到水平井的垂直距离的比值变化而变化,当比值为1.4时采出程度最大;水平井注CO_2更适合低渗透正韵律储层;在储层裂缝发育的情况下,裂缝条数越多,CO_2在储层中的不均匀推进现象越明显,最终采出程度越低。

According to the existing weakness of oil displacement by CO2 with vertical well pattern in low-per-meability reservoir,the article first takes some low-permeability blocks in Daqing as an example to build a geo-logic model of oil displacement by CO2 with inverted seven-spot horizontal well pattern.Based on the phase be-havior matching of physical parameters,comparative study is demonstrated between the development effects of inverted seven-spot horizontal well pattern and five-spot vertical well pattern,and the other parameters of invert-ed seven-spot horizontal well pattern are optimized,meanwhile,the influential factors of the reservoir heteroge-neity (e.g.permeability,heterogeneity of the reservoir,fracture development state and so on)are also ana-lyzed.Results show that:the development effects of the horizontal wells pattern are better than that of the verti-cal wells pattern under the same conditions;In the horizontal wells pattern,the recovery varies with the vertical distance ratio of production to injection,and the recovery is the highest when the ratio is 1 .4;Horizontal wells pattern with CO2 injecting is more suitable for low permeability positive rhythm reservoir;In the case of the res-ervoirs with fracture development,the more the number of fractures is in the reservoir,the more obvious the phenomenon of non-uniform advancing is,the lower the ultimate recovery is.