低渗油藏水驱后注CO2补充能量机理及方式优化

Mechanisms and optimization of supplementing in?鄄situ energy by CO2 injection after water flooding in low permeability reservoirs

王智林 林波 葛永涛 姚富来 李晓南

中国石化江苏油田分公司勘探开发研究院，江苏 扬州 225009

Exploration & Production Research Institute, Jiangsu Oilfield Company, SINOPEC, Yangzhou 225009, China

注CO2是解决水驱后低渗油藏压力下降快、能量恢复难问题的有效方式。文中将水驱后低渗储层划分为水相未波及区、无（弱）水敏伤害区及水敏伤害区，针对其成因分别揭示了CO2接触动用孔隙中剩余油、恢复储层能量的机理，提出了注气开发中的异步注采方法，并采用数值模拟方法对比了常规连续注气、周期段塞注气及异步注采3种方式下的开发指标。结果表明：周期段塞注气一定程度延缓了气窜时间，开发效果略好于连续注气；异步注采方式在宏观上抑制气窜、增大波及体积和微观上增加CO2与原油接触的双重作用下，采出程度和换油率均高于连续注气，分别比连续注气提升了4.30，0.12百分点。以增油量和换油率为评价指标，优选了异步注采方式下储层压力恢复水平界限，结果显示，最优压力恢复水平为1.10倍最小混相压力。

CO2 injection is an effective way to solve the problem of rapid pressure drop and difficult energy recovery of low permeability reservoir after water flooding. In this paper, the low?鄄permeability reservoir after water flooding is divided into the unswept area of water phase, the area with water sensitive damage and the area without damage, and the mechanism of contact between CO2 and the residual oil in pores and recovery of reservoir energy is demonstrated respectively according to its causes. The asynchronous injection?鄄production method in gas injection development is presented, and the production parameters of conventional continuous injection, periodic slug injection and asynchronous injection?鄄production are compared by numerical simulation method. The result shows that delaying gas channeling timing makes periodic slug gas injection achieve a better developing effect than continuous injection. And for asynchronous injection?鄄production, inhibiting gas channeling, increasing the sweep efficiency macroscopically and enhancing the contact effects between CO2 and oil phase microscopically contributes to its advantage over continuous injection, with an increase of 4.30% of recovery and 0.12% of oil change rate, respectively. Taking oil increase and oil change rate as evaluation indexes, the boundary pressure of formation is determined, and the result demonstrates the optimal pressure of formation after CO2 injection is 1.1 times of the minimum miscible pressure.

10.6056/dkyqt201902020