新疆吉木萨尔凹陷致密油藏最小混相压力实验研究

最小混相压力是油田采取注CO2增产方式的重要参数之一,为了确定新疆吉木萨尔凹陷芦草沟组致密油藏原油与CO2的最小混相压力,进行了室内细管实验和界面张力实验。结果表明,细管实验测得新疆致密油藏最小混相压力值为18.70 MPa,略大于界面张力实验测得最小混相压力值18.44 MPa,二者相差1.4%,均小于油藏压力43.00 MPa,因此在现有油藏条件下CO2与原油能实现混相;平衡压力越大,CO2溶于原油后界面张力降低越多,当系统平衡压力从0.73 MPa增大到28.46 MPa时,原油与CO2的界面张力值由22.62 mJ/m2降到1.83 mJ/m2;当平衡压力在0.73~13.33 MPa时,CO2在原油中的溶解占主导作用,当平衡压力在15.84~28.46 MPa时,CO2对原油中轻质组分的萃取占主导作用,且原油与CO2相互作用机制由CO2溶解度向CO2萃取轻质组分转变时的压力为13.67 MPa。通过实验研究,加深了对目标油藏最小混相压力及原油与CO2微观相互作用机理的认识,为目标油藏注CO2增产开发方案的制定提供理论支持。

Experimental Investigation on Minimum Miscible Pressure of the Tight Oil Reservoir in Jimsar Sag,Xinjiang

The minimum miscible pressure is one of the important parameters of CO2 injection in oil field. In order to determine the minimum miscible pressure between crude oil and CO2 in the tight reservoir of lucaogou formation, jimusar sag, Xinjiang, the laboratory slim tube test and interfacial tension test were carried out. The results show that the MMP measured by slim tube test in Xinjiang tight oil reservoir is 18.70 MPa, slightly higher than the MMP measured by the interfacial tension experiment, which is 18.44 MPa. The difference between the two is 1.4%, and both lower than the reservoir pressure of 43.00 MPa. Therefore, CO2 and crude oil can be miscible under the reservoir conditions. When the equilibrium pressure increases, the IFT decreased more as more CO2 dissolved in crude oil. When the system equilibrium pressure increased from 0.73 MPa to 28.46 MPa, the IFT value between crude oil and CO2 decreased from 22.62 mJ/m2 to 1.83 mJ/m2. When the equilibrium pressure was between 0.73 MPa to 13.33 MPa, the dissolution of CO2 in crude oil took the leading role. However, when the equilibrium pressure was between 15.84 MPa to 28.46 MPa, the extraction of light components in crude oil took the leading role, and the interaction mechanism between crude oil and CO2 changes from CO2 solubility to CO2 extraction of light components at the pressure of 13.67 MPa. Through the experimental study, the understanding of the MMP of the target reservoir and the microscopic interaction mechanism between crude oil and CO2 is deepened, which provided theoretical support for the formulation of CO2 injection development of the target reservoir.