Engineering

Enhanced-Oil Recovery (EOR) for asset acquisition or rejuvenation involves intertwined decisions. In this sense, EOR operations are tied to a perception of high investments that demand EOR workflows with screening procedures, simulation and detailed economic evaluations. Procedures have been developed over the years to execute EOR evaluation workflows.

This work is motivated by the need for inexpensive carboncapture technology for combustion-based power plants. Such power plants produce electricity by converting coal or natural gas to carbon dioxide (CO2), which is normally vented as an 11%-12% component of flue gas that contains a balance of nitrogen and other minor components. Separating CO2 from such a flue-gas mixture poses no special technical problems for the known absorption, pressure-swing adsorption (PSA), and membrane technologies. However, these technologies have a tendency to be expensive for two principal reasons: the hot flue gas is produced at low pressure and the separated component (CO2) is highly dilute with an inert component (nitrogen).

The first-ever collaborative field demonstration project conducted by Osage Partners LLC, TIORCO, Chemical Tracers Inc., and the Enhanced Oil Recovery Institute (EORI) was completed in the Bradley Unit of the Osage oil field in October. The purpose of this project was to collect an in situ measurement of residual oil saturation from the reservoir. The single-well chemical tracer test also evaluated the effectiveness of an alkali-surfactant-polymer (ASP) to mobilize stranded oil.

The simulation evaluation concluded that gravity stable CO2 flooding can be an effective EOR method for the Grieve Muddy reservoir. Up to 23 MMBO could ultimately be recovered by gravity stable CO2 flooding. The reservoir has potential to sequester more than 145 BSCF of CO2 at the end of CO2 flooding operation. Prior to the simulation of history matching and CO2 flooding, a four-layer Petrel model of Grieve Muddy reservoir was developed based on the identified facies in the Muddy channel sand and the overlain sandstone interval of bay-head delta deposition. Porosity and permeability distributions of layers generated in the Petrel model were exported to the simulation model. An OOIP estimation of 67 MMBO in Grieve Muddy channel sand has resulted from a simulation history matching based on the full-field material balance. History matching also reveals that about one MMSTBO of oil and 8.2 BSCF of gas have moved down from the overlain low-permeability sandstone interval into the Muddy channel sand interval during the reservoir depletion.

Grieve oil field was discovered in August 1954. The field is located in southeastern Wind River Basin, central Wyoming, and is currently operated by Elk Petroleum Inc. (Elk Petroleum), Figure 1. The producing oil reservoir is a stratigraphic/structural trap at a depth of 6,900 ft in the Lower Cretaceous, valley-fill and channelized, Muddy sandstone. The average structural dip in the Grieve area is about 15 degrees to the northeast.

This Tensleep Formation Fracture Study compendium contains the field studies, core analyses and literature reviews conducted over the 2007-2010 period in an effort to understand the characteristics and distributions of fractures and their influence on fluid flow within Tensleep Formation reservoirs. The studies reported here are the results of a large-scale project on fractures in the Tensleep Formation in Wyoming initiated by the Enhanced Oil Recovery Institute (EORI) at the University of Wyoming. The supporting data are also available through EORI and can be utilized in a variety of modeling software.

• The thermodynamic characterization of reservoir and injected fluids allows us to perform rigorous analyses of the oil recovery processes.
• A continuous program that will reveal important factors that are still unknown or not well understood and affecting the efficiency of oil recovery.
• A synthesis of theoretical and experimental components.