Laboratory perforation tests were conducted shooting into target formation core at downhole-matching conditions in order to select the best perforating system for optimized production in a viscous oil-saturated, unconsolidated sandstone reservoir. Along with determining depth of penetration, the need was to find the optimal casing hole size for cyclic steam stimulation, requiring smaller holes for effective steam distribution, and holes large enough for minimal velocity during the production cycle.
The first step was to process the crude oil-saturated, unconsolidated sandstone cores taken from the target zone to enable their use with minimal disturbance. Once the cores were prepared such that specific field stress and pore pressure could be applied, shaped-charge perforators were shot to determine resultant hole-entry sizes and depths of penetration. Besides investigating casing hole size which regulates the flow-velocity/drawdown-pressure relationship, other insight gained was understanding the difference between solvent versus heat displacement of the viscous crude oil.
The focus of the testing began with the perforation behavior in the stressed, viscous crude oil-saturated sand, then flow of the viscous crude oil through the sand, and finally on how the viscous crude oil-flow behavior was affected by heat to lower viscosity. Results showed that penetration into the stressed formation core was sufficiently deep regardless of the shaped charge size and the main constituent for shaped charge selection was the diameter of the casing entrance hole. Tests using heat to assess its effectiveness on improving crude oil flow through the sand showed to be most effective while minimizing undesired sand movement.
At the time this abstract was written, multiple wells had been recently perforated and are currently under field evaluation and data gathering, to be compared to the laboratory findings. This paper will include discussion on the testing process used and the effect of perforating the viscous crude oil sand. It will also offer insight into the effects of increasing the temperature of the viscous crude oil and selecting a perforating strategy.