[solops]

Originally posted by David E. Gervais:
I remember someplace I heard that the oil companies are pumping something like 10 galons of fresh-water into the oil wells for every 1 gal of petrolium that they take up.

Water floods use salt water pumped from water supply wells out of water bearing rock strata, filtered down to 5-20 microns (and sometimes chemically treated) and then injected into the target oil reservoir in injection wells, which are drilled in a carefully calculated pattern designed to allow the water to "sweep" the oil toward producing wells. Normal oil fields have a recovery efficiency of 8 to 13%. Water floods can sometimes increase this efficiency to 30%.

Water requirements for a flood are huge and fresh water is not really a viable alternative in most cases. Salt water is available in the earth in huge quantities. Also, few things are more destructive to oil and gas reservoirs than fresh water, which causes clay swelling, emulsions, precipitates and other nasty things. Many wells are completed using fresh or salt water treated with chemicals, but the volumes are small - a few hundred or thousand barrels. Waterfloods require water volumes in the hundreds of thousands or millions of barrels, even when the water used is produced and recycled into the flood.