Ann: Grieve EOR Project Progess Report , page-20

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Re your Grieve LITE, if the financials and terchnicals are ok I favour the slow approach and the smart use of incremental prod’n to further increase prod’n. But there are issues.

One financial drawback re Elk is the $2m+pa of admin expense which ticks away and depletes the revenue left for productive reinvestment above. Perhaps too many chiefs.

Re technicals, the problems of partial reservoir treatment are linked to pressure and dissipation (thus efficiency) of the injected material. The most efficient long term recovery option is always to condition the whole field. I’m familiar with steam injection by individual well. The energy and pressure progressively dissipates into the field. The treatment becomes less effective in the area you’re trying to treat. Better to do the whole field if possible.

The University of Wyoming estimated that for the CO2 EOM of Grieve you’d need to first re-pressurise the reservoir (the whole field), with a cumulative injection of 90 BSCF or more of CO2 - before any production begins (Note that involves significant upfront material and energy pumping cost, and applies to chemical injection as well). Gas fairly readily dissipates through the field, so any attempt to pressurise and inject C02 in just one area gets quickly diluted.

Surfactants (in water) won’t dissipate quite as readily and you might be aided by the buoyancy of oil in treating a smaller area. If you don’t re-pressure the whole field, at a minimum you need to generate a pressure gradient between the injector and pumping wells. Generally the smaller the area of the field you try to treat, the greater the untreated area tends to thwart your efforts re pressure and dilution. You will also inevitably end up pushing some oil away from the collector wells. Individual well flow rates become less predictable with a bias to lower rates if you opt to treat a smaller %’s of the field.

So a balancing act between likely lower pumping performance v’s lower capital costs. My gut reaction is that 25% is the smallest area you would try it on and ideally that area would have some sort of partial separation from the rest of the field. In practice you are always dealing with some unknowns and it will come down to an educated guess even with all available info at hand.