CO_2对原油的抽提及其对原油黏度的影响

CO2 extraction for crude oil and its effect on crude oil viscosity

采用高压PVT（压力-体积-温度）试验装置，模拟3种不同性质的原油油样非混相驱时CO2-原油的接触过程，重点考察CO2对原油的抽提作用以及CO2抽提后剩余原油的物性，测定抽提过程中进入气相的轻质组分的体积（抽提油量）、残余油黏度及组成。试验结果表明：CO2优先抽提原油中的轻质组分，原油越轻，CO2的抽提油量越大；抽提后残余油黏度普遍提高，残余油样黏度是原油黏度的1．1—2．0倍，且温度越低，黏度比越大；提高注入压力或降低CO2注入量可防止油气性质差异变大。研究认为，抽提作用对重质原油的黏度影响较大，导致CO2抽提后残余油的采出难度加大，建议CO2驱油技术应优先应用在轻质油藏。

With high-pressure PVT （pressure-volume-temperature） experimental device, extraction experiments were con- ducted using three different crude oil samples, and the contact process of CO2 and crude oil in immiscible flooding was simu- lated in PVT container. The ability of CO2 extraction for crude oil and the properties of residual oil after CO2 extraction were studied. The volume fraction of light components entering the gas phase, viscosity and composition of residual oil in the process of extraction were measured. The experimental results show that the light components of crude oil are preferentially extracted by CO2 , and the lighter the crude oil, the bigger the extraction volume. After extraction the residual oil viscosity increases and is 1.1 - 2.0 times of the crude oil viscosity. The lower the temperature, the bigger the viscosity ratio. The difference between oil and gas can be minimized by increasing injection pressure or decreasing CO2 injection volume. The ex- traction has an important impact on heavy oil viscosity, and results in more difficult to recover the residual oil. It is recom- mended that CO2 flooding technology should be applied priority to the light oil reservoirs.