定边S油区长4+5油层注水开发影响因素分析

Influence Factors of Water Injection Development of C4+5 Oil Reservoir in Dingbian S District

定边S油区长4+5油层为特低渗储层,油气开采难度大。长4+5油藏注水开发过程中,存在注水压力大、油井供液不足、产量递减快等问题。为了改善该区注水开发效果,通过对岩心储层孔隙结构进行精细研究,利用测井曲线对夹层进行识别,结合井网和注水质量分析,得出以下结论:对于长4+5储层中胶结物晶间孔中的残余油,由于其孔隙半径小,注水水水驱作用甚微;适量夹层增加了油层水洗厚度,增加油层的水驱效果,但过量的夹层使厚砂体成为多个薄砂体,储层整体渗透性变差,开采方式应以小层为单位按单砂体合注合采,增加纵向上各单砂体的动用程度,改善开发效果;注采井网不对应,须进行统层调层以提高水驱控制程度;注入水悬浮物和含油量较高,以及注入水存在与地层水不配伍、发生沉积的现象,须对注入水水质严格按标处理。

C4+5 Oil reservoir in Dingbian S district is an ultra-low reservoir, it is difficult to develop the oil reservoir.In the process of waterflooding development of C4+5 reservoir, the problems of high waterflooding pressure, insufficient fluid supply and rapid production decline were prominent. In order to improve the effect of water injection development in this area, the pore structure of core reservoir was studied, and logging curves were used to identify interlayer, well pattern and the quality of injected water were analyzed. The result showed that, the water drive of water injection had little effect on residual oil in intergranular pore of cement of C4+5 reservoir which had small pore radius. Proper amount of interlayer increased the thickness of reservoir water washing to improve the water drive-effect of reservoir. However the excessive interlayer made the thick sand body into many thin sand bodies that caused the permeability of the whole reservoir become worse. In this case the development mode based on small layer should combine injection and production according to single sand body in order to improve development effect. Aiming at injection-production well pattern problem, the layer-by-layer adjustment should be carried out to improve the degree of waterflooding control. Aiming at high content of suspended matter and oil, or the incompatibility of water quality and formation water, the quality of injected water should be treated strictly according to the standard.