CHOPS (Cold Heavy Oil Production with Sand) is a primary production recovery method used in the Western Canadian Lloydminster heavy oil region which contains about 3 billion m3 of heavy oil. It increases heavy oil production rates by creating high permeability channels in the reservoir through aggressively producing sand with the oil. As a result of CHOPS, 5 - 15% of the initial oil can be recovered.
This paper summarizes CHOPS history matches that used the CMG STARS™ simulator and representative process mechanisms in simulating two Husky CHOPS wells, one well was later used as a Cyclic Solvent Injection (CSI) pilot well and the second well was a communicating offset well during CSI. The history matches were pre-processed for the post-CHOPS CSI field pilot. They were part of the $40 million JIVE Program and were in support of a CSIfield development in the Edam area.
The history matches predicted the reservoir conditions (e.g. pressure, effective permeability, effective porosity, fluid saturations, and mole fraction profiles) at the end of CHOPS to set up the CSI initial reservoir conditions (i.e. the start of CSI). Oil, water and sand production were well matched for both of the wells during CHOPS. Foamy oil and sand transport mechanisms were represented in the simulations. The simulation results and the CHOPS model described below provided insight into CHOPS depletion mechanisms and post-CHOPS reservoir characteristics.
At the end of CHOPS, the CSI well was pressure depleted with low liquid inflow. In the simulations, the wormholes were predicted to extend to about 151 m from the CSI well. Wormholes from the offset well reached a source of water and had continuous water inflow. It was predicted that the offset well wormholes penetrated about 220 m into the reservoir.
The AITF CHOPS model can capture field production mechanisms and reservoir behaviors.
Continuing lower rate sand production and wormhole network growth is essential to obtain sustained higher oil production rates during CHOPS.
As a result of greater reservoir contact, a thinner pay with longer wormholes can produce more oil than a thicker pay with shorter wormholes.
Directly obtaining reservoir properties from the field LAS log data and use of the thin layers in the log file as simulation layers were important in catching fluid flow behaviors and obtaining satisfactory history matches for oil and water production.
Good CHOPS history matches and reservoir charactisation are essential for field CSI pilot wells as they quantify the post-CHOPS reservoir conditions, the extension of wormhole networks, and the depletion regions. Consequently, they provide predictive value for developing CSI operation strategies for successful post-CHOPS CSI applications.