河流相稠油油田合理注水时机实验研究

Experimental Study on Reasonable Water Injection Opportunity in Heavy Oil Fields in Fluvial Facies

针对河流相稠油油藏衰竭开发转注水开发注水时机难以确定的问题,以渤海秦皇岛32-6油田油藏参数为基础,通过物理模拟的手段寻求最佳注水时机。首先确定油田各区块的最佳衰竭压力,然后在原始地层压力和最佳衰竭压力之间选取5个压力点进行注水时机模拟实验,同时开展注水过程中是否需要恢复压力至原始地层压力的对比实验。结果表明:各区块最佳衰竭压力为饱和压力的90%~96%,且原油黏度越大,最佳衰竭压力越接近饱和压力;注水时机选择在最佳衰竭压力时,可获得较高的无水采油期和采收率,且累计注水量最少;注水恢复压力至原始地层压力开发并不能提高开发效果,反而耗水量增多。因此,河流相稠油油田合理注水时机推荐最佳衰竭压力附近,能有效利用天然能量,获得较高的采收率,且可减小注水量,降低生产成本。该结论和认识在数值模拟中也得到了验证,对同类油藏的开发具有指导和借鉴意义。

For solving the problem that the water injection opportunity changed from depletion development of heavy oil reservoirs in fluvial facies is hard to confirm, on the basis of reservoir parameters of the Qinhuangdao 32-6 oil- field in Bohai Sea, we tried to find the optimum water injection opportunity by physical simulation. Firstly, we con- firmed the optimum depletion pressure for each block of this oilfield ; after that, we selected five pressure values be- tween the initial formation pressure and the optimum depletion pressure to do physical simulation experiments for confirming water injection opportunity; meanwhile, we conducted cmnparison experiments for determining whether it is necessary to restore the pressure to initial formation pressure during water injection. The study result shows that： （1） the optimum depletion pressure of each block is 90%-96% of the saturation pressure; （2） the bigger crude oil viscosity, the closer of the optimum depletion pressure to the saturation pressure; （3） if the water injec- tion is conducted at the optimum depletion pressure , we can obtain longer water free oil production period and high- er recovery ratio, and the total injected water quantity is the minimum; （4} the development effect cannot be im- proved by restoring the pressure to the initial formation pressure, but＇leading to more water consumption. Hence, we recommend the reasonable water injection opportunity to he near the optimum depletion pressure, which can effec- tively utilize natural energy, obtain higher recovery ratio, reduce injected water quantity, and decrease production cost. This conclusion and cognition has been verified by numerical simulation, thus it has guiding and referring sig- nificance for developing similar oil reservoirs.