低渗储层全直径岩心对CO_2相变影响的实验研究

为了研究储层孔隙介质对CO2注入地层后相态的影响情况,建立了真实岩心中相变的超声波测试方法.对比CO2在低于临界温度26.0℃和高于临界温度48.0℃两种情况下,分别在超声波测试装置、空筒、DBRPVT分析装置中的相变情况.对比可以得出:①在临界温度以下,孔隙介质的存在对CO2相变点的影响不大;②临界温度以上时,孔隙介质的存在使CO2的p-V关系曲线的拐点值有比较大的降低,从空筒中测试的10.89 MPa降到5.51 MPa;③温度对CO2在孔隙介质中的p-V关系曲线的拐点的影响比较小;④超声波在测试孔隙介质中CO2的相变点时,振幅变化比较明显,时差的变化比较小.

Experiment research of the phase transition of carbon dioxide in the true core of low permeability reservoir

In order to study the effect of the media in reservoir pore on the phase transition of the carbon dioxide injected into the reservoir,the ultrasonic testing method for the state of carbon dioxide in true core is established.The phase transition of carbon dioxide is monitored in ultrasonic testing device,empty canister and DBRPVT analysis device at the 26.0 ℃ under critical temperature and the 48.0 ℃ above critical temperature separately.And the results show that,① under critical temperature,the existence of pore media has little influence on the phase transition point of carbon dioxide;②over critical temperature,the existence of pore media makes the pressure greatly decrease at the inflexion of the p-V relation curve of carbon dioxide,which decreases from 10.89 MPa in empty canister to 5.51 MPa in true core;③ temperature has little influence on the inflexion of the p-V relation curve of carbon dioxide in pore media;④ there are obvious variation of amplitude and less variation of time difference in the ultrasonic testing of the phase transition point of carbon dioxide in pore media.