水平井CO_2吞吐增油机理及影响因素

Enhanced Oil Recovery Mechanism and Influence Factors of CO_2 Puff and Huff in Horizontal Well

为了探究底水稠油油藏水平井注CO_2吞吐机理及影响因素,针对M油田G104-5油藏,开展了注CO_2膨胀实验并建立了单井注CO_2吞吐数值模拟模型,研究了G104-5油藏稠油注CO_2膨胀后的相态变化和注气工艺参数、油藏参数对水平井注CO_2吞吐的影响,并在此基础上进行了G104-5油藏7口水平井的注CO_2吞吐效果试验。结果表明,注入35 mol%CO_2后,M油田G104-5油藏稠油的黏度降低了45%,体积膨胀系数为1.13,饱和压力升高了200%,原油中C_9~C_(22)的摩尔分数下降了14.4 mol%。薄层底水油藏注CO_2吞吐增油时,效果最好的直井(射开1~3层)措施后平均含水率降至87%,累计增油313.17 t,水平井措施后平均含水率降至75%,累计增油679.91 t,水平井增油控水效果较好;在所有的影响参数中,注气量、油层厚度、含油饱和度、孔隙度是影响水平井注CO_2吞吐效果的主控因素,注入速度、焖井时间、采液速度、地层压力和渗透率对水平井CO_2吞吐效果的影响不大。M油田G104-5油藏7口吞吐井中G104-5P101井孔隙度最大(45%),注气量最大(412 t),累计增油量最多(1412.27 t)。

In order to research the enhanced oil recovery mechanism and influence factors of CO2 puff and huff in horizontal well in heavy oil reservoir with bottom water, the CO2 swell experiments was carried out and CO2 puff and huff single well simulation model was built in view of G104-5 reservoir of M oilfleld. The phase changing after CO2 swell, and the influence of technological parameters of gas injection and reservoir parameters were studied, and the CO2 puff and huff of 7 horizontal wells from G 104-5 was conducted. It is concluded that after injected 35mol% CO2. the viscosity of heavy oil decreased by 45% and the coefficient of cubic expansion was 1.13, and saturation pressure increased by 200% and mole fraction of C9-C22 in oil decreased by 14.4mol%. After CO： puff and huff in the thin bottom water reservoir, the water cut of vertical Well （shoot layer from 1 ;to 3）, which had 313.17 t cumulative incremental oil, decreased to 87%, while the water cut of the horizon well, the cumulative incremental oil being of 679.91 t, decreased to 75%, which indicted that the latter had better oil-increment and water-control effect. Among all of the effect parameters, the gas volume, reservoir thickness, oil saturation, porosity was the most important parameters; while the injection speed, formation pressure, shut time, exploit speed and permeability had little effect in CO2 huffand puff With horizon well. In the 7 CO2 huffand puff wells of G104-5 reservoir, G104-5P101 had the biggest porosity （45%）, the maximum injected gas volume （412 t）, and the most cumulative incremental oil （ 1412.3 t）.