Abstract
In the Pikes Peak oil field near Lloydminster, Canada, a significant amount of heavy oil reserves is located in reservoirs with a bottom water zone. The properties of the bottom water zone and the operation parameters significantly affect oil production performance via the steam-assisted gravity drainage (SAGD) process. Thus, in order to develop this type of heavy oil resource, a full understanding of the effects of these properties is necessary. In this study, the numerical simulation approach was applied to study the effects of properties in the bottom water zone in the SAGD process, such as the initial gas oil ratio, the thickness of the reservoir, and oil saturation of the bottom water zone. In addition, some operation parameters were studied including the injection pressure, the SAGD well pair location, and five different well patterns: (1) two corner wells, (2) triple wells, (3) downhole water sink well, (4) vertical injectors with a horizontal producer, and (5) fishbone well. The numerical simulation results suggest that the properties of the bottom water zone affect production performance extremely. First, both positive and negative effects were observed when solution gas exists in the heavy oil. Second, a logarithmical relationship was investigated between the bottom water production ratio and the thickness of the bottom water zone. Third, a non-linear relation was obtained between the oil recovery factor and oil saturation in the bottom water zone, and a peak oil recovery was achieved at the oil saturation rate of 30% in the bottom water zone. Furthermore, the operation parameters affected the heavy oil production performance. Comparison of the well patterns showed that the two corner wells and the triple wells patterns obtained the highest oil recovery factors of 74.71% and 77.19%, respectively, which are almost twice the oil recovery factors gained in the conventional SAGD process (47.84%). This indicates that the optimized SAGD process with the two corner wells and the triple wells pattern is able to improve SAGD production performance in a heavy oil reservoir with a bottom water zone.
Highlights
The steam-assisted gravity drainage (SAGD) process can be optimized by controlling the injection pressure and the location of the producer to gain better production performance [13]
When the SAGD process is applied in a reservoir with a bottom water zone, the most serious issue is that the bottom water will invade the oil pay zone and be produced from the producer
The existence of a bottom water zone has a negative effect on heavy oil production performance
Summary
The remarkable production potential of heavy oil in Canada has been widely reported [1,2,3,4,5,6,7,8]. From studying the effects of different well patterns, scholars found that well pattern affects the production performance significantly They found that, first, in a high water cut heavy oil reservoir, the water cut can be reduced significantly from 90% to 60% by using a combination of vertical injectors and horizontal producers. The single vertical well SAGD process to screen the reservoir was considered as a quicker way to predict the SAGD production performance than the horizontal SAGD pilot test in the Pikes Peak oil field [22] Numerical simulation is another efficient approach to study the SAGD process applied in the heavy oil reservoir with a bottom water zone. The well are bottom water zone) is defined to indicate the heavy oil production performance, and the relationships optimized using the most effective well patterns, and the oil recovery factors can reach almost twice among the defined parameter and the reservoir properties are correlated. Wong et al [32]; b Miller and Xiao [33]; c Akbarzadeh et al [38]
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