低渗透油藏再生氮气泡沫驱实验与应用

针对常规氮气泡沫在地层消泡后难以再次起泡,严重制约泡沫驱效果的问题,开展室内实验,采用多因素评价方法,从发泡能力、再次起泡性能、耐盐、耐温耐压等方面优选出廉价高效的再生氮气泡沫驱油配方体系。在模拟油藏条件下,开展了一维岩心驱替实验,证实了再生泡沫的可行性,对比并优选出合理的注入参数:气液比为3∶1,注入速度为0.3～0.4 mL/min,气液同注。在新疆油田SN井区开展了2个井组的先导试验,累计注入0.43倍孔隙体积的再生氮气泡沫段塞,日增油8 t/d以上,井组含水下降6.6个百分点,并在后续水驱中通过再次起泡持续增油,累计增油4 947 t,投入产出比达到1.0∶1.6。该研究表明再生氮气泡沫驱能有效提高原油产量和采收率,在同类油藏具有重要应用潜力。

Test and Application of Regenerative Nitrogen Foam Flooding in Low-Permeability Reservoirs

The conventional nitrogen foam is difficult to re-foam after defoaming in the formation, which severely restricts the effect of foam flooding, laboratory tests were conducted to select an economical and efficient regenerative nitrogen foam flooding formulation system in terms of foaming capacity, re-foaming performance, salt resistance and temperature resistance and pressure resistance with a multi-factor evaluation method. One-dimensional core displacement test was conducted under simulated reservoir conditions to confirm the feasibility of regenerative foam and select the reasonable injection parameters: the gas-liquid ratio was 3∶1, the injection rate was 0.3-0.4 mL/min, and the gas and liquid were injected simultaneously. Pilot tests were conducted in two well clusters in SN well block, Xinjiang Oilfield. The regenerative nitrogen foam plug of 0.43 times of pore volume was injected cumulatively, and the daily oil increase was more than 8 t/d, and the water cut of the well cluster decreased by 6.6 percentage points. In the subsequent water flooding, the oil production was enhanced by re-foaming to 4 947 t, and the input-output ratio reached 1.0∶1.6. It is found in the study that regenerative nitrogen foam flooding can effectively improve the oil production and recovery, with important application potential in similar reservoirs.