考虑原油脱气对压力函数影响下的油井产能研究

Study on a New Productivity Equation for Oil-well by Considering the Impact of Oil Degassing on Pressure Function

油井生产中,当压力低于饱和压力后,原油会在地层脱气,井筒附近形成三相流,影响油井产量。本文根据渗流力学理论,针对大多数油井在生产过程中,只是在井底附近局部脱气,而在远离油井的较大区域内尚未形成脱气的情形,建立了油井脱气半径及产能计算公式,重点分析了井底流动压力降低对油井脱气半径以及油井产能的影响。研究结果表明:油井井底流动压力低于饱和压力后,井底附近会形成脱气区域,并随井底流动压力的降低,其脱气半径将逐渐增大;采用文中建立脱气条件下油井产能计算公式能够准确反映脱气对油井产能的影响,弥补传统达西公式在脱气条件下计算油井产能的不足,为油井进行放大生产压差生产时合理产能的确定提供可靠的理论方法。

In the process of oil well production,crude oil degassing will happen in reservoir when the pressure is lower than the saturation pressure, which lead to three phase flow near wellbore, bringing a strong impact on oil production. In view of this phenomenon of many oil wells degassing happened near bottom-hole area, a method of calculating degassing radius and productivity equation were established according to the theory of percolation mechanics in this paper. The results show that when the flowing bottomhole pressure is lower than the saturation pressure, a degassing area can form. With the decreasing of formation pressure, the degassing radius increases gradually. Using the established well productivity formula can accurately reflect the effect of well degassing on well productivity, as well to make up the deficiency of the conventional Darcy formula for calculating the oil well production under the condition of degassing. The equation provided reliable theoretical method to determine reasonable productivity in liquid enhanced wells.