隔夹层对巨厚砂岩油藏注气开发的影响——以塔里木盆地东河1油田石炭系油藏为例

塔里木盆地东河1油田石炭系油藏为巨厚砂岩储层,层内发育的隔夹层对注气开采有重要影响,其对注气的封隔能力决定了注气提高采收率是采用分层动用还是整体动用的开发策略。通过隔夹层岩心物性测试和气体突破压力测试实验,再结合数值模拟计算,研究了注气时隔夹层的封隔能力。实验结果表明:隔夹层渗透率以小于0.01 mD为主,其渗流能力低;干岩心突破压力较低,但一旦被水或油饱和,突破压力大幅度增大,其封隔能力也大幅度增强,岩心的封隔能力则主要受渗透率和隔夹层内流体饱和度的影响。数值计算表明:对渗透率为0.008 mD、厚度为0.2 m的隔夹层,当隔夹层连续时,注气过程中通过隔夹层窜流到临近小层的气窜量不到总注气量的5%,这说明连续隔夹层对注气具有很强的封隔能力;当隔夹层不连续时,隔夹层的展布范围则对其封隔能力有着重要的影响。

Effect of interlayers in thick sandstone reservoir for gas injection: a case study of Donghe 1 Carboniferous oil reservoir in Tarim Basin

The Carboniferous oil accumulation in Donghe 1 Oilfield of Tarim Basin is a huge thick sandstone reservoir, where the interlayer has a significant influence on gas-injection development. The isolation ability of the interlayer determines that whether the gas injection is a development strategy to improve recover using the layered or overall development. The isolation ability of interlayer in gas injection was studied through tests on the physical properties of interlayer cores and gas breakthrough pressures in combination with numerical simulation and calculation. Experimental results have shown that the permeability of interlayer is mainly less than 0.01 mD, indicating a lower permeability; the breakthrough pressure of dry core is lower. Once the interlayer is saturated by water or oil, the breakthrough pressure will increase greatly, as well as the isolation ability, and the latter is mainly influenced by permeability and fluid saturation in the interlayer. The results of numerical calculations indicate that as for the interlayer with the permeability of 0.008 mD and the depth of 0.2 m, the amount of gas channeling from interlayer to adjacent small layers accounts for less than 5% of the total gas injection volume during gas injection in case of a continuity in interlayer, showing the high isolation ability of interlayer in gas injection. If the interlayer is discontinuous, the distribution range of interlayer has a great influence on isolation ability.