二氧化碳驱油藏开发指标计算方法研究

Study on Calculation Method of Development Index for Carbon Dioxide Flooding Reservoir

20世纪60年代,Koval基于水驱油相关理论(Buckley-Leverett水驱油非活塞理论)及二氧化碳混相驱特性(即混相驱油藏不存在界面张力,各相渗透率与对应相饱和度成正比),推导出二氧化碳混相驱流动模式下气体分流系数及采出程度与注入流体孔隙体积倍数关系式。Koval模式考虑了影响气驱效果的三个主要因素,即油藏的非均质性、原油黏度和累计注入量。本文基于Koval的研究成果,开展了二氧化碳驱油藏主要开发指标计算方法研究,将油藏实际开发数据与Koval模式理论曲线拟合,通过反复试凑油藏动用储量,直到两者数据充分拟合满意为止,可求得注气驱油藏动用储量,进而求得油藏采出程度、累计产气量、存气率及换油率等开发指标随注入量的变化曲线。通过苏北CS油田泰州组油藏实际开发数据拟合计算,求得的该油藏动用储量与容积法计算储量基本一致,理论产气量与实际产气量、理论换油率与实际换油率基本吻合。

In the 1960s,based on the correlated theory of water flooding(Buckley-Leverett non piston fluid displacement theory)and carbon dioxide miscible flooding characteristics(namely,the interfacial tension does not exist in miscible flooding reservoirs and permeability of each phase is proportional to the corresponding phase saturation),Koval deduced relational expression between gas diverting coefficient,recovery degree and pore volume multiple of the injected fluid in flow mode of carbon dioxide miscible flooding.The Koval model considers three main factors that affect the gas flooding,namely reservoir heterogeneity,oil viscosity and cumulative injection volume.In this paper,based on the research achievements of Koval,calculation method of the main development indexes for CO2 flooding reservoir is studied.The real reservoir development data is matched with theoretical curves of Koval model until the data fitting is satisfied through repeated trial on produced reserves of the oil reservoirs,and the produced reserves in gas flooding reservoir may be calculated.And then the curve of reservoir recovery degree,cumulative gas production,gas storage rate,oil change rate,and other development indexes changed with the injection volume may be obtained.Based on the fitting calculation of the actual development data of Taizhou Formation oil reservoir in CS Oilfield in northern Jiangsu,the calculated produced reserves are basically consistent with the reserves calculated by volume method,the theoretical gas production and the theoretical oil displacement efficiency are basically consistent with the actual one respectively.