It is frequently to adopt casing head gas assisted lifting technology to reduce the adverse effects of gas on pump efficiency in the wells with high gas-liquid ratio and make full use of gas energy. A gas lift valve is lowered to the appropriate depth to re-inject the annulus gas into the tubing. In this way, the systematic efficiency is improved by using the gas lifting principle. However, the source and pressure of casing head gas cannot be controlled artificially, and gas injection pressure and injected gas volume are varied over the time. To verify the rationality of design parameters, a dynamic model was developed for the process of casing gas assisted lifting based on the flowing characteristics of each section in oil production system and the operating characteristics of oil production equipments. In this model, the volume and pressure change of casing head gas caused by downhole separators and gas lift valves are taken into account. Production parameters of oil wells with and without downhole separator and gas lift valve were compared. It is shown that after the cas-ing head gas assisted lifting system is adopted, the pump efficiency of oil wells is improved, the casing pressure is under control and the upstroke load is reduced. It is indicated that casing head gas can be used to assist artificial lift. Finally, the effects of all parameters in the process of oil production were investigated by changing the setting depth, size and starting pressure of gas lift valves. The research results provide the basis for the design of casing head gas assisted lift technologies.%在高气液比井中为了减少气体对泵效的不利影响,同时又能充分利用气体能量,采用套管气辅助举升技术是一个比较经济有效的选择.在井下合适深度下入气举阀,将环空气体返注回油管,利用气举原理可获得更高的系统效率.然而套管气源和压力无法人为控制,注气压力和注气量均随时间变化.为了验证设计参数的合理性,结合采油系统中各段的流动特点和采油设备的工作特性,考虑井下分离器和气举阀造成的套管气体量以及压力的变化,建立了套管气辅助举升过程的动态模型.通过比较有无井下分离器及气举阀时的油井生产参数变化,得到使用套管气辅助举升系统后,油井泵效提高、套压得以控制、上冲程载荷降低等结果,表明套管气可以用来辅助人工举升.研究还通过改变气举阀下入深度、直径以及开启压力,研究各参数对采油过程的影响,为套管气辅助举升工艺的设计提供了依据.
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