丙烷与二甲醚辅助SAGD开采规律二维物理模拟实验

Two-dimensional physical simulation experiment of propane and dimethyl ether assisted SAGD

蒸汽辅助重力泄油技术(SAGD)是一种成熟的稠油热采技术,但其开采后期,随着蒸汽腔与盖层接触面积进一步增大,散热量增加,驱油效率降低,累计油汽比下降。在SAGD中、后期采用转轻烃溶剂辅助的接替技术,选择二甲醚作为辅助溶剂,并选取丙烷作为对照,进行了3组二维可视化实验,全程监测产油和产液速率、产出液含水率、原油采收率、累计油汽比和溶剂回收率,并揭示了温度场和蒸汽腔的变化规律。实验结果表明,SAGD开采主要分为蒸汽腔向上发育、蒸汽腔横向扩展以及蒸汽腔向下发育3个阶段。蒸汽腔扩展到盖层边界,即达到SAGD开采中-后期,产油速率下降明显。在SAGD中-后期加入溶剂后,产油、产液速率均有明显上升。SAGD的采收率为53.67%,累计油汽比为0.141,相比之下丙烷辅助SAGD采收率提高了11.91%,累计油汽比提高了0.012;二甲醚辅助SAGD采收率提高了19.26%,累计油汽比提高了0.027。二甲醚的回收率为86.6%,比丙烷回收率高出6.9%。

Steam-assisted gravity drainage(SAGD)is a mature thermal recovery technology for heavy oil.However,in the later stage of exploitation,as the contact area between steam chamber and cap rock further increases,the heat dissipation is increased,the oil displacement efficiency is decreased,and the cumulative oil-steam ratio declines.This paper investigated the replacement technology for injecting light hydrocarbon solvent in the mid-late period of SAGD.Using dimethyl ether as the auxiliary solvent and propane as the control,three sets of two-dimensional(2-D)visualization experiments were carried out to monitor the oil production,liquid pro-duction rate,water cut of produced liquid,crude oil recovery,cumulative oil-steam ratio and solvent recovery,and also discover the changes of temperature field and steam chamber.The experimental results show that SAGD recovery is mainly divided into three sta-ges:upward development of steam chamber,lateral expansion of steam chamber,and downward development of steam chamber.When the steam chamber has extended to the boundary of cap rock,i.e.,in the mid-late stage of SAGD production,the oil produc-tion rate is decreased significantly.After adding solvent in the mid-late stage of SAGD,oil production and liquid production rate are increased significantly.Compared with the oil recovery of 53.67%and accumulative oil-steam ratio of 0.141 in SAGD process,pro-pane-and dimethyl ether-assisted SAGD can increase the oil recovery by 11.91%and 19.26%,as well as the accumulative oil-steam ratio by 0.012 and 0.027,respectively.The recovery of dimethyl ether is 86.6%,which is 6.9%higher than that of propane.