特低渗透裂缝性油藏超前注水井网评价方法

大庆油田外围某特低渗透试验区天然裂缝发育,微裂缝一方面可以增大油、水渗流能力,另一方面会加剧注入水窜流,认清裂缝发育特低渗透油藏超前注水的水平井井网部署对开发效果的影响是很有必要的。考虑特低渗透油藏非线性渗流规律,对微裂缝采用等效渗流介质理论,运用室内岩心分析数据和数值模拟的方法,探讨了超前注水水平井井网部署。根据井网与微裂缝匹配关系,建立12套模拟模型。通过分析各方案采出程度与含水率关系、地层压力保持水平和压力梯度场分布,明确了各方案的开发效果和适应性。分析结果表明水平井井筒垂直于最大主应力方向井网开发效果好。七点水平井网开发效果好,应优化井距以驱动注水井间的原油。九点井网见水快,应合理设计注水井位置,避免过早见水。水平井五点井网不适用于该地区。

Evaluation Method of Advanced Water Injection Wellnet of Special-Low Fractured Reservoir

There are lots of natural fractures in a special-low permeability experimental formation of outer Daqing oil field.On one hand,natural fractures can enhance the seepage ability of water and oil,on the other hand,it will aggrabate the channeling flow of the injection water.It’s necessary to recognize the effect of horzontal well net by advanced water injection of fractured special-low permeability reservoir.The nonlinear seepage law of special-low permeability reservoir is considered,used equivalent continum media theory and inerior core analysis data,to discuss the methods of horizental well network in advanced water injection by numerical simulation.According the matching relationship of wellnet and fractures,12 simulation models are established.By analyzing the relationship between recovering degree and water ratio,remain level of formation pressure,and distribution of pressure gradient,the development effect and adaptibility of each plan are clarified.The results reveals that plans in which the horizontal oil well is perpendicular to the direction of maximum principal have better development effects,and seven-spot wellnet has better effect,which can drive more crude oil by decreasing distance between the injection wells.Nine-spot wellnet see water quickly,which should adjust the position of injection wells to avoid water influxing too fast.While five-spot horizontal well net is not sutable to this area.