In Cerro Negro, extra-heavy crude (8.5° API) is produced using horizontal wells via cold production from Miocene Morichal Member sands. Production is from an average depth of 3,000 ft, with an in-situ viscosity of around 2,000 cp (@140° F). The Morichal Member is sub-divided into three informally defined units: Upper, Middle and Lower. Reservoir quality is excellent, with porosity around 32% and permeability in the order of 10 Darcies.

The top of the Morichal sands varies in depth from 1,500 to 4,000 ft. The depth of the sand, coupled with 700-900 ft reservoir thickness, results in significant changes in pressure and viscosity across the block. Pressure varies from 900-1,300 psi and viscosity from 1,500-4,000 cp. Pressure and viscosity variations, when modeled using a single well simulation grid, significantly affect well productivity and ultimate recovery. Changes in viscosity and pressure, assuming constant pay thickness, and permeability, result in predicted ultimate well recoveries that vary from 1.5 to 6 million barrels of oil per well. Efforts to history match horizontal wells that have been on production for around one year have been successful. These results give a better understanding of how fluid and rock properties are influencing extra-heavy crude oil recovery, which allows a better prediction of well productivity and full-field development plans.

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