特低渗透油藏合理注气能力和开发效果分析

THE APPROPRIATE CAPACITY AND DEVELOPMENT EFFECT OF GAS INJECTION IN EXTREMELY LOW-PERMEABILITY RESERVOIRS

针对国内外特低渗透砂岩油藏及大庆外围芳48断块地质特点,在开展室内油水和油气相渗透实验的基础上,应用油水及油气渗流理论和油藏工程及气藏工程方法,分析了特低渗透砂岩油藏油水和油气渗流特征、采油指数与吸水指数、采油指数与吸气指数、油层破裂压力和注气能力的关系,研究出了特低渗透油藏注气能力设计方法,并在芳48断块注气方案设计中得到有效应用。研究表明:芳48断块特低渗透扶余油层具有常规特低渗透砂岩油藏的渗流特征,采油能力和吸水能力低,吸气能力较高,在合理注入压力下具有一定的注气能力,注气比注水开发效果好。矿场试验结果证实,芳48断块注入产能设计指标与矿场实际开采结果相近,注气压力较低,油层吸气能力强,油井产量明显高于类似的水驱油藏的产量,说明注气开发是提高特低渗透油藏动用程度的有效途径,为类似油藏注气开发提供了有效的方法。

In view of the geological characteristics of the extremely low-permeability sandstone reservoirs in China and abroad and Block Fang 48 in Daqing periphery; based on the laboratory experiment of oil-water and oil-gas permeation and the application of the filtration theory for oil reservoir engineering and gas reservoir engineering, it is analyzed the relations between oil-water and oil-gas percolation characteristics, oil recovery index and water injectivity index, oil recovery index and gas injectivity index, formation frac pressure and capacity of gas injection, and it is also developed the method to design the gas injection capacity in extremely low-permeability reservoirs. It has been used in the gas injection project in Block Fang 48. The research showed that Block Fang 48 displayed the regular characteristics of the extremely low-permeability reservoirs, low oil production, low water injection capacity and high gas injection capacity. The gas injection has better exploitation effect than water injection under appropriate injection pressure. The field experiment proved that the actual production results of Block Fang 48 were close to the designed gas injection capacity. The gas injection pressure was low. Oil formation had strong gas injection capacity. The oil production was obviously higher than that produced by water injection. All indicate that gas injection is an effective approach to enhance the extremely low-permeability reservoirs production, and provide a more effective way to exploit the reservoirs with similar natures.