While SAGD (Steam Assisted Gravity Drainage) can be used to recovery heavy oil from strong bottom water drive reservoir, the bottom water is known to have a detrimental effect on the SAGD performance, may cause unsuccessful SAGD application. During SAGD process, the common practice to control the water encroachment is to keep the steam chamber pressure at or above the aquifer pressure. At higher pressure, less latent heat is available, leading to unprofitable SAGD project with low oil production rate and low oil recovery.

In this paper, an innovative approach is proposed to tackle the problem by combining the use of SAGD with DWS (Downhole Water Sink). The concept of DWS is the first to be integrated into SAGD production process. With a new type of well completion design, along with the two separated wells of SAGD, another well is completed in the water zone to decrease the aquifer pressure through continuous water production. As the aquifer pressure decreasing, low steam chest pressure can be maintained, thus allowing for more latent heat available in the formation which would ensure high oil rate and high oil recovery.

A theoretical study of SAGD-DWS performance on improving heavy oil recovery is conducted in this paper. A design model is developed to predict the optimum ranges of the SAGD-DWS production parameters under various operation scenario. The effects of the new approach on increasing oil rate and improving oil recovery in comparison to that of conventional SAGD are quantified. The results demonstrate that unlike other thermal recovery methods, the combined use of SAGD with DWS can prevent the water invasion into the steam chamber while allowing for low steam chamber pressure with high heat efficiency.

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