CO_(2)-CH_(4)气体节流及水合物生成特性

CO_(2)-CH_(4) Gas Throttling and Hydrate Generation Characteristics

CO_(2)驱采油举升过程中,随着压力的降低,采出液会析出大量伴生气,伴生气中CO_(2)含量高达50%~90%,相比CH_(4)气体,气态CO_(2)节流致冷效应更强,引起的低温可能会生成水合物堵塞管道,威胁集输系统的运行安全。采用高压蓝宝石反应釜研究了CO_(2)含量对CO_(2)-CH_(4)气体节流及水合物生成特性的影响。结果表明:当初始压力为高压(16 MPa)时,相同CO_(2)占比的混合气体,节流效应系数Di约为1.3~5.4℃/MPa,CH_(4)的掺入将增强混合气体节流效应,说明高压段主要受CH_(4)节流效应的影响;当初始压力为低压(5 MPa、4 MPa)时,节流效应系数Di约为3.4~11.9℃/MPa,CH_(4)的掺入将减弱混合气体节流效应,说明低压段主要受气相CO_(2)节流效应的影响;相同CO_(2)含量的CO_(2)-CH_(4)气体所处压力越高,水合物生成的温度越高,越容易生成水合物;在相同压力下,CO_(2)含量越低,生成水合物温度越低;CO_(2)含量在8%~100%,压力在1.5~5 MPa,水合物生成温度为0.5~10℃。实验与软件模拟数据对比结果表明PR状态方程对CO_(2)-CH_(4)的节流及水合物生成特性计算具有较高的相关性。研究结果可为安全集输工艺参数的选择提供参考。

In the process of CO_(2) flooding production and oil lifting,with the decrease of pressure,a large amount of associated gas will be separated from the produced liquid.In the associated gas,the content of CO_(2) is as high as 50%-90%.Compared with CH_(4),gaseous CO_(2) has a stronger throttling cooling effect,which may cause the generation of hydrate to block the pipeline,threatening the operation safety of the gathering and transportation system.The influence of CO_(2) content on the CO_(2)-CH_(4) gas throttling and hydrate generation characteristics was studied using a high-pressure sapphire reactor.The results show that:When the initial pressure is high(16 MPa),the throttling effect coefficient Di of the mixture gas with the same CO_(2) proportion is about 1.3-5.4℃/MPa,and the incorporation of CH_(4) will enhance the throttling effect of the mixture gas,indicating that the high pressure section is mainly affected by the throttling ef-fect of CH_(4);when the initial pressure is low(5 MPa,4 MPa),the throttling effect coefficient Di is about 3.4-11.9℃/MPa,and the in-corporation of CH_(4) will weaken the throttling effect of the mixture gas,indicating that the low pressure section is mainly affected by the throttling effect of gaseous CO_(2).The higher the pressure at which CO_(2)-CH_(4) gases with the same CO_(2) content are,the higher the temper-ature at which hydrates are generated,and the easier it is to generate hydrates.At the same pressure,the lower the CO_(2) content is,the lower the temperature at which hydrates are formed.When the CO_(2) content is 8%-100%and the pressure is 1.5-5 MPa,the hydrate generation temperature is 0.5~10℃.The comparison results between the experimental and software simulation data show that the PR equation of state has a high correlation for the calculation of CO_(2)-CH_(4) throttling and hydrate generation characteristics.The research results can provide a reference for the selection of safe gathering and transportation process parameters.