Luncheon – September 17, 2010

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Talk: Reservoir Characterization of the Grieve Muddy Sandstone for Enhanced Oil Recovery

Speaker: Chris Mullen

Location: Denver Marriott City Center

Date: September 17, 2010

Abstract: Published in The Outcrop, September 2010

Fifty five years and 30 million barrels of oil after the field was discovered by Forest Oil the Grieve Field is still giving up secrets that will produced up to 50% more oil.

Gas injection began in 1959 for pressure maintenance in the field. Blow down of the gas cap began in 1978. While in the pressure maintenance phase of the field wells were constantly being shut in when gas/oil ratios exceeded tolerable limits. This production methodology stranded hundreds of thousands of barrels of oil in the reservoir. No true secondary recovery was ever conducted in the field.

In the last five years, Elk has been evaluating the field for different methods of enhanced oil recovery. Before any new evaluation for EOR was conducted a revised reservoir model was developed. Beverly DeJarnett with the Bureau of Economic Geology in Houston was contracted to review the existing core at the USGS in Denver. A three layer incised valley model was generated for the field. Induction and Micrologs were then used to complete the full field model for EOR history matching and simulation.

The Grieve Muddy channel is characterized by a thick southeast to northwest trending incised valley. The basal unit in the valley (Facies A) is a fine to medium-grained, cross stratified sandstone that represents the true fluvial deposition. This sequence grades into a rippled and burrowed unit interpreted to have been deposited in a fluvial-estuarine point bar or bay head delta. This unit is capped by a mud rich estuarine sandstone.

This three dimensional model of the Grieve Sandstone was first used to define the CO2 EOR potential of the field. After all attempts to secure CO2 were exhausted, the field is now being evaluated for Alkaline Surfactant Polymer flooding.