Perforating of Multiple Tubingless Completions

Published in Petroleum Transactions, AIME, Volume 219, 1960, pages 88–93. Abstract The perforating of multiple tubingless completions, in which two or more strings of 2 7/8-in. OD casing are installed in the same borehole, presents two basic problems. First, good completion practices require an efficient perforator that leaves no debris to interfere with subsequent completion operations. Second, and of more complicated nature, a system is needed for controlling the direction of fire so that adjacent strings are not damaged. Development of a 2-in. OD, steel, retrievably, shaped-charge gun has solved the first problem. The second was resolved through development of three different devices to provide directional perforating for the two types of completion methods being employed today. These include a mechanical orienting device and two self-orienting radiation devices. Conceivably, the latter methods could be adapted to the directional perforating (of upper zones) of conventional dual and triple completions without removing production tubing and packers. Introduction The recent trend to multiple tubingless completions, wherein two or more strings of 2 7/8-in. OD casing are installed in the same borehole, has presented two basic perforating problems. The first problem to be overcome was the design of a gun that would result in efficient perforations without causing debris to bridge in these small-diameter casings. The second problem was, of course, to devise a system for controlling the direction of fire such that adjacent strings would not be damaged. The problem of gun debris in slim-casing completions has been well defined in the numerous 2 7/8-in. single tubingless completions which have been effected during recent years with the expendable-type perforators. Failure of expendable-gun debris to settle out properly, even with good gun break-up, has resulted in bridging inside these small-diameter casings. This, in turn, has interfered with completion and re-conditioning operations.