The pressure injection disposal well completed for the U. S. Corps of Engineers at the Rocky Mountain Arsenal, 10 miles northeast of Denver, exemplifies a revolutionary concept in industrial waste disposal. This method is one which has been used by the oil industry for many years. The well has two major distinctions: it is the deepest well drilled in the Denver Basin, and it may provide a precedent for solving waste disposal problems which are anticipated in the future industrial growth of the Denver area.
The well was drilled on the east flank and near the axis of the Denver Basin and penetrated Tertiary through pre-Pennsylvanian sediments. Drilling was completed at a depth of 12,045 feet in Precambrian gneiss. The sediments from Tertiary through Pennsylvanian are in normal sequence. They show only minor variations in thickness and lithology from sections in adjacent areas. The occurrence in this part of the Denver Basin of pre-Pennsylvanian sediments, possibly Ordovician in age, was unexpected and may shed valuable light on the paleography of the Denver area.
Lost circulation was a major drilling problem in the Paleozoic sediments and in the Precambrian gneiss. Slow penetration rates resulting from the induration of the Paleozoic sediments necessitated the use of special hard-formation drilling bits. Core information shows that the Permian and Pennsylvanian sediments are fractured and have a rock matrix of low porosity and permeability. Drill-stem tests indicate that the Paleozoic sediments contain low-pressure reservoirs.
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Prepared by the Case Histories Committee for the Engineering Geology Division of the Geological Society of America, these histories are intended as reference material for the practicing geologist and for the college student. This volume, the eighth in the Case History series, presents the seismological aspects of the works of man—the civil engineer or engineering geologist interacting with the environment. Topics are in two categories—changes at a point (nuclear or chemical explosions and well injection or withdrawal) and changes on a line (damming a river or construction along a coastline).