LAUSR

Abstract Steam-assisted gravity drainage (SAGD) is an efficient technology that has been used to develop oil sand resources, and it has been successfully and maturely applied in Canada. However, oilfield production has demonstrated that reservoir heterogeneity has a serious impact on SAGD development, among which the most drastic impact is caused by multiple barrier layers in the reservoir. These barrier layers can severely impede the development of a steam chamber and the drainage of oil. Hence, it is important to investigate their influence mechanism. In this study, oil samples from the Long Lake oil field were used in laboratory experiments to study the development of the steam chamber and the residual oil distribution under the effect of multiple barrier layers. Then, a theoretical numerical simulation model was established to describe the fluid flow more precisely. In addition, the production characteristics of SAGD under the influence of different numbers of barrier layers were analyzed by comparing the development of the steam chamber. Finally, the impacts of multiple barrier layers with different modes of combinations were studied for their effects on SAGD production. The results indicated that for impermeable barrier layers of the same length, the steam primarily developed upward after flowing around the first barrier layer. After the steam chamber reached the top of the reservoir, the steam began to enter into the interbedded zone. Based on an unchanged first barrier layer, the number of barrier layers had little influence on the overall shape of the steam chamber and SAGD production, which confirmed that the first barrier layer played a dominant role in the influence of multiple barrier layers. In addition, characteristic points (P1, P2, P3), which corresponded to changes in the stage of steam chamber development, were established and used to evaluate the effect of the barrier layers. Different combinations of barrier layers were realized by changing the relative properties of the first barrier layer. The results showed that the longer the length of the first barrier layer, the closer it was to the steam injection well and the lower the permeability; hence, the more obvious its hysteresis effect on the SAGD process.