凝析气藏循环注气新方法

NEW METHOD OF CYCLIC GAS INJECTION FOR CONDENSATE RESERVOIRS

凝析气藏循环注气开发注干气受气源及天然气价格因素影响较大 ;注氮气则可以节省宝贵的天然气资源 ,但会引起凝析气藏露点压力升高而造成一定量的凝析油损失。文章以实际凝析气藏为例 ,提出干气—氮气交替注入方法开发凝析气藏的方法 ,可发挥干气对析出凝析油的反蒸发作用 ,而将氮气作为一种单纯的驱替介质 ,减小因氮气与凝析气接触后导致露点压力升高而引起的凝析油损失。文章还利用数值模拟方法研究注气时机、储层非均质、段塞尺寸等因素对开发效果的影响 ,结果表明利用干气—氮气交替注入开发凝析气藏 ,其凝析油采收率分别比枯竭式和注氮气高 31.8%和 2 .8% ,同时可以减少 5 0 %的干气回注量 ,极大地提高了凝析气藏开发的经济效益。

In the process of cyclic gas injection to develop condensate reservoirs, the method of dry gas injection is limited when the source of gas is not abundant or the price of natural gas is too high. Nitrogen injection can save the valuable resource of natural gas, but may cause the dew point pressure rising and some condensate loss. With real condensate reservoirs, the article proposes the method of alternate injection by dry gas and nitrogen to develop condensate reservoirs. By this way, the dry gas can work for anti-vaporization of condensed oil and the nitrogen will work just as a driving medium to reduce the condensed oil loss caused by dew point pressure rising since the nitrogen contacts with condensate. With numeral simulation, the influence of the gas-injecting time, the heterogeneous of reservoirs and the size of plug column on the development of reservoirs is studied. The results show with the method of alternate injection by dry gas and nitrogen to develop condensate reservoirs, the recovery factor of condensed oil is 31.8% and 2.8% higher than that with the depleted development and nitrogen injection respectively. Also, 50% of back-injecting dry gas is saved, and the economic benefit of condensate reservoir development is improved greatly.