空气泡沫驱数学模型与数值模拟方法

A mathematical model and numerical simulation method for air-foam flooding

为了描述空气泡沫驱过程中空气与泡沫的运移规律和复杂的驱油机理,通过相与组分关系的相关假设,借鉴火烧油层数学模型方法,结合空气低温氧化动力学方程、泡沫驱经验数学模型与物化参数的处理,建立了空气泡沫驱数学模型,分析了该模型的封闭性,并提出了相应数值模型的求解方法。建立了概念模型,通过空气泡沫驱室内实验拟合修正了氧化动力学模型,并模拟评价了空气泡沫低温氧化驱油机理影响因素的敏感性。结果表明,室内实验各阶段驱替效果与见水时间的拟合都比较好;空气泡沫驱效果更好、成本更低,适合于非均质油藏(变异系数0.7～0.8)或注水开发后期正韵律油藏;采用高温高压、高注低采、水驱至含水率96%左右时转泡沫驱以及反七点井网等方式,都有利于增强空气泡沫的驱油效果;当气液比为1∶1～2∶1、空气注入速度0.1～0.2 PV/a,以及采用空气泡沫/空气交注注入方式时,驱油效果最佳。

To describe movement laws and complex flooding mechanisms of air and foam during the air-foam flooding, we built a mathematical model for the air-foam flooding based on an assumption of the correlation between phases and components. This model used the mathematical model of in-situ combustion as reference and combined the processing of physicochemical parameters with an air low-temperature oxidation dynamics equation and an empirical model of the foam flooding. The present paper examined the clo- sure of this model and proposed a solution way to corresponding numerical models. A concept model was built and the oxidation dy- namics model was modified through an experimental match with the air-foam flooding, and consequently the sensitivity towards influ- ential factors for the displacement mechanism of the low-temperature oxidation flooding was assessed in an air-foam flooding simula tion. The result shows that the displacement effect is matched considerably well with the water breakthrough time during the whole experiment. The air foam flooding characteristic of a better effect and lower cost is fit for heterogeneous reservoirs with variation co efficients between 0.7-0.8 or for positive-rhythm reservoirs in the late water flooding stage. Many methods can be beneficial to in- creasing the air-foam flooding effect, such as high temperature and pressure, water injection at higher position while production at lower position, switchover to the foam flooding as the moisture content reaching to 96% by the water flooding and an inverted seven- spot well pattern in the water flooding. Besides, a better flooding effect can be also achieved as the gas liquid ratio keeps between 1 ： 1-2 ： 1, the air injection rate ranges in 0.1 -0, 2 PV/a or the air-foam alternating-air injection pattern is applied.