Abstract

This paper summarizes a study that was part of the $40 million Joint Implementation Vapor Extraction Program and was in support of a planned solvent (60% CH4 – 40% C3H8) injection field pilot at Fort Kent, Alberta where CHOPS wells are prolific oil producers. The pilot design was for a horizontal well between and below four vertical wells. The vertical wells were to be on CHOPS before becoming solvent injectors with the horizontal well as a producer.

CHOPS simulations were based on matching specified oil production. The simulations utilized an AITF CHOPS model (with CMG STARS™ as a platform) to design CHOPS operating strategies. The CHOPS simulations determined: (a) wormhole penetration length required to maintain the specified oil rate, (b) when to stop CHOPS and start solvent injection, and (c) the initial conditions (wormhole occupied region, fluid saturations, etc.) for solvent injection simulations. The predicted post-CHOPS reservoir properties were transferred to a reservoir model that represented part of the proposed well arrangement and was used in the solvent injection simulations.

Conclusions from the post-CHOPS solvent injection simulations included:

  • During the post-CHOPS re-pressurization period, solvent should be injected in the horizontal well as well as the vertical wells. This strategy reduces subsequent channeling between the vertical and horizontal wells.

  • Solvent injection performance depends on: (a) lateral offset between vertical injectors and horizontal producer, (b) layers in which vertical wells are perforated, (c) maintained pressure difference between injectors and producer, (d) operating pressure, and (e) gas production rate.

  • Oil rates were significantly reduced by spreading of injected solvent in the high permeability region created by wormholes and by displacement of oil in this region away from the wells.

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