The method of reverse-circulation drilling was designed primarily for drilling large-diameter production wells in unconsolidated formations. The practical minimum diameter (about 16 in.) for drilling holes by the reverse-circulation method almost precludes its being used for test-hole drilling. However, this method provides the best cuttings samples of any drilling method because of the large intake capacity of the bit (5 in. or more); this method also provides fast delivery of cuttings to the surface because of high ascending velocities (can be several hundred feet per minute) of the drill cuttings and fluid. Therefore, reverse circulation is an excellent drilling method for obtaining cutting samples. Ibr those readers interested in the method, comprehensive descriptions are provided in "Water Well Techology" (Campbell and Lehr, 1973) and "Ground Water and Wells" (Universal Oil Products, 1966).
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