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在过去的 4 0年里 ,人们一直在研究稠油油藏注蒸汽的机理 ,而对轻质油藏注蒸汽则研究得很少 ,对这一过程的机理和作用还不太了解 ,对于向裂缝性轻质油藏中注蒸汽的机理更是知之甚少。本研究利用热组分模拟检验低渗透裂缝油藏的热效率。岩石模型采用硅藻岩。油相由相对较轻的具有轻质油相似特征的三种拟组分代替。与水驱相比 ,平面及垂向采收率都有了很大提高。采收率的增加值取决于渗透率的分布 ,均质油藏采收率提高幅度最大。机理方面的研究表明 ,在蒸汽驱早期 ,烃类流体的热膨胀作用对采收率的作用最大 ,采收率的增加值约占总增加值的 5 0 % ;注入孔隙体积的 4 0 %以后 (在水驱基础上 ) ,提高采收率的机理为热膨胀作用、蒸馏作用以及原油降黏作用 ;当蒸汽带突破至生产井时 ,油井的生产动态受蒸馏作用影响。由于注入蒸汽的影响 ,在注采井间形成三个彼此相互独立的流体带 :冷水带、热水和蒸汽混合带以及蒸汽前缘。因而 ,轻质油藏蒸汽驱油机理完全不同于稠油油藏。在稠油油藏 ,蒸汽驱油机理主要是原油降黏作用和重力分离作用。虽然本次实验采用的是硅藻岩和流体模型 ,但其机理同样适用于一次采油以及水驱采收率极低的低渗透、裂缝性油藏。对这些油藏 ,主要是通过实施蒸汽驱来提高采收率。
In the past 40 years, people have been studying the mechanism of steam injection in heavy oil reservoirs. However, little attention has been paid to the steam injection of light oil reservoirs, and the mechanisms and functions of this process have not been well understood. The mechanism of steam injection in fractured light reservoirs is poorly understood. In this study, thermal component simulation was used to test the thermal efficiency of low permeability fractured reservoirs. The rock model uses diatomite. The oil phase is replaced by the relatively lighter three pseudo-components with similar characteristics of light oil. Compared with waterflooding, both horizontal and vertical recovery have been greatly improved. The recovery of oil recovery depends on the distribution of permeability, and the recovery rate of homogeneous oil reservoir increases most. Mechanism studies show that in the early stage of steam flooding, the thermal expansion of hydrocarbon fluids has the greatest effect on oil recovery, and the added value of recovery rate accounts for 50% of the total added value. After 40% of the pore volume is injected On the basis of waterflooding), the mechanisms of enhanced oil recovery are thermal expansion, distillation and viscosity reduction of crude oil. When the steam strip breaks through to production wells, the production dynamics of oil wells are affected by distillation. Due to the influence of steam injection, three separate fluid zones are formed between injection and production wells: cold water, hot water and steam mixing zone and steam front. Therefore, light oil reservoir steam flooding mechanism is completely different from the heavy oil reservoir. In heavy oil reservoirs, the main mechanism of steam flooding is the role of oil viscosity reduction and gravity separation. Although this experiment uses diatomite and fluid models, its mechanism is equally applicable to low-permeability fractured reservoirs with primary oil recovery and very low waterflood recovery. For these reservoirs, oil recovery is mainly used to enhance oil recovery.