海上稠油油藏水平井多元热流体驱物理模拟实验研究

Experimental study on multi-thermal fluid flooding by using horizontal wells in offshore heavy oil reservoirs

受海上采油平台的限制,实施注蒸汽热力采油的难度较大,而多元热流体技术发生设备体积小,因此具有非常大的应用潜力。为此,利用一维填砂管模型,研究注入温度和流体组成对多元热流体驱油效果的影响;在此基础上,通过二维比例物理模拟实验,开展水平井多元热流体驱物理模拟研究,通过分析多元热流体驱不同阶段的生产动态特征与温度场发育规律,总结多元热流体驱的驱油机理。研究结果表明:多元热流体驱的最佳注入温度为250℃,最佳气汽比为1∶3;多元热流体驱过程中,蒸汽腔呈三角形推进,整个过程可划分为启动、驱替、突破和剥蚀4个阶段,其中驱替阶段是主要的产油阶段;多元热流体驱主要机理包括:热力降黏是其最主要的机理,二氧化碳溶于原油而促进原油流动,二氧化碳析出时形成类似泡沫油的流体,一方面增大气相的流动阻力,另一方面又能改善原油的流动能力。

Due to the limitation of oil production platform,it is difficult to carry out thermal recovery in offshore heavy oil reservoirs by steam injection. The technology of multi-thermal fluid has a great potential to develop the offshore heavy oil reservoirs because of its small equipment size. A long sand-pack tube model was used to analyze the influence of injection temperatures and fluid component on oil displacement by multi-thermal fluid,and then a 2D physical simulation with the similar scale was carried out to study the production performance and the distribution characteristics of temperature field. Finally,the mechanism of oil displacement was summarized. The results show that the best injection temperature is 250 ℃ and the best gas and steam ratio is 1∶3 for the multi-thermal fluid flooding. During the flooding,the steam chamber gradually advances from injection well to production well in a triangle mode. The whole process of flooding can be divided into four stages:start-up,displacement,steam channeling,and erosion. Among them,the highest oil production is from the displacement stage. The main mechanism of EOR involves thermal viscosity reduction,oil mobility increasing due to the dissolution of CO2,the formation of foam-like fluid during the precipitation of CO2 to increase the flow resistance of the gas phase and to improve the movability of crude oil.