海相砂岩油藏天然能量开发界限研究

Study on Limit of Natural Energy Development in Marine Sandstone Reservoirs

南海珠江口盆地的海相砂岩油藏一般采用天然能量开发,但也发现部分含油面积大的油藏存在天然能量不足的问题,需要注水开发。为避免平台后期注水改造等诸多问题,有必要开展海相砂岩油藏开发方式的界限研究。分析了影响开发方式的地质因素主要有水体大小、储层渗透率及地层原油黏度和油藏含油面积等。基于27个已开发海相砂岩油藏生产资料,天然能量开发的油藏流度高、含油面积小,当含油面积大于某一界限时,水侵速度小于油藏产液速度,油藏内部能量不足而采用注水开发,其含油面积界限随油藏流度增大而增大。采用油藏数值模拟方法研究得到海相砂岩油藏天然能量开发的含油面积界限与油藏流度的定量关系式,当油藏流度大于160×10^(-3)μm^(2)/(mPa·s)时,只要油藏含油面积小于5km^(2),即可采用天然能量开发。该方法计算结果与南海珠江口盆地已开发的典型油藏能量认识的吻合率为100%。某油藏实际压力监测数据表明油藏能量不足,也与本方法的认识一致。

The marine sandstone reservoirs in the Pearl River Mouth Basin of the South China Sea are generally developed with natural energy.It is found that some reservoirs with large oil-bearing areas have insuffi-cient natural energy and need waterflood development.In order to avoid the issues of waterflood reconstruction in the later period for the platform,it is necessary to study the limit of development scheme of marine sandstone reservoirs.The geological factors affect the development scheme include water body size,permeability,oil viscosity and oil-bearing area of reservoirs.Based on the production data of 27 developed marine sandstone reservoirs,the oil reservoirs developed with natural energy has high mobility and small oil-bearing area.When the oil-bearing area is larger than a certain limit,the water invasion rate is less than the liquid production rate of the reservoirs,and the waterflood development is adopted for insufficient internal energy of the reservoirs.The oil-bearing area limit increases with the increase of reservoir mobility.The quantitative relationship between oil-bearing area limit and reservoir mobility of natural energy development in marine sandstone reservoirs is studied by reservoir numerical simulation method.When the reservoir mobility is greater than 160×10~(-3)μm~2/(mPa·s),it may be developed with natural energy as long as the oil-bearing area of the reservoirs is less than 5km~2.The agreement rate of this method is 100%with that of the typical reservoir energy in the Pearl River Mouth Basin.The actual pressure monitoring data of a reservoir shows that the reservoir energy is in-sufficient,which is also consistent with the understanding of this method.