高压注气过程中沥青质沉淀机理及规律的实验研究

EXPERIMENT ON PRECIPITATION AMOUNT AND MECHANISM OF ASPHALTENE IN HIGH-PRESSURE GAS INJECTION PROCESS

提出了一种新的注气开采过程中沥青质的沉淀机理 ,该机理可定性解释及预测高压注气过程中沥青质的沉淀规律。在高压沥青质沉淀实验装置上 ,利用间接测定法测定了CO2 注入摩尔分数分别为 0 .6 36和 0 .716时吉林油藏原油中沥青质沉淀量随体系压力的变化规律 ,并测定了 2 2 .2MPa下 70℃时江苏原油中沥青质沉淀量随CO2及富烃气注气浓度的变化规律。实验结果表明 ,在注气过程中两种原油易发生沥青质沉淀。吉林油藏原油中的沥青质沉淀量随体系压力的升高呈先增后降的规律 ;当体系温度和压力一定时 ,江苏原油中的沥青质沉淀量先随着CO2 注入浓度的增加而增加 ,达到一最高值后略有降低 ;对注富烃气而言 ,沥青质沉淀量随注气浓度增加而增加 ,且注气摩尔分数大于 0 .80后增加幅度增大。

A new precipitation mechanism of asphaltene under high pressure gas injection condition was proposed. It can be used to explain and predict the asphaltene precipitation behavior qualitatively during the process of gas injection. By using the apparatus for experiment on high pressure asphaltene precipitation and the indirect determination method, the variations of the amount of asphaltene precipitation with the change of system pressure for oil from Jilin reservoir were measured when CO 2 injection concentrations were 0.636 and 0.716 (molar fraction)respectively. The variations of the precipitation amount of asphaltene of degassed oil and crude oil from Jiangsu reservoir under the conditions of 22.2 MPa and 70 ℃ while changing the injection concentration of CO 2 and hydrocarbon rich gas were also measured. The results show that asphaltene precipitation was easily induced for the two kinds of oils during gas injection, and the precipitation amount of asphaltene of oil from Jilin reservoir increased with the increasing pressure of the system firstly and then decreased after it reached a zenith. The variation of asphaltene precipitation with increasing CO 2 injection concentration was the same. However, the precipitation amount of asphaltene increased continuously while increasing concentration of hydrocarbon rich gas, and a more rapid increase was observed as the molar fraction of the hydrocarbon rich gas exceeded 0.80.