预测注CO_2过程中沥青质沉淀新方法

A NEW METHOD FOR PREDICTING ASPHALTENE PRECIPITATION BY USING P-T PHASE GRAPH DURING CO2 INJECTION

对注CO2过程中出现第二液相的相态进行了分析,并从P-T相图的计算方法出发,分析了注CO2过程中第二液相的出现引起的P-T相图的不稳定性。结合P-T相图能表征第二液相及第二液相与沥青质沉淀的关系,文章首次提出用P-T相图用于预测沥青质的沉淀。文中将未注CO2状况下,注CO2多次接触及长岩心驱替过程的流体物性数据作P-T相图,得出表征第二液相的特性P-T图与实验和模拟数据相符。提出的P-T相图预测注CO2过程沥青质沉淀方法能简便地预测沥青质沉淀及定性地分析沥青质沉淀动态,对分析含沥青质原油注CO2过程中沥青质沉淀具有重要的参考价值。

In the experiment, the second liquid phase is observed during CO2 flooding the asphaltic oil, and the phase state of the second liquid phase was analyzed. Based on the calculation method of P-T phase diagram, the stability of P-T phase behavior graph caused by the second liquid phase was evaluated. Combing the ability of P-T phase behavior presenting the second liquid phase and the relationship between the second liquid phase and asphaltene precipitation, the method, asphaltene precipitation predicted by P-T phase behavior, was presented. Thus, in order to verify the feasibility of the method, a series of cases were used, such as the multiple contacts of CO2 and long core flooding experiments. Through case analysis, the results indicated that the P-T phase diagram that could characterize the second liquid phase behavior was consistent with the experiment and simulation results. Thus, the method presented in this paper could predict the asphaltene precipitation and analyze the asphaltene precipitation dynamic, which would be practical method in the judgment of asphaltene precipitation during CO2 injection.