depending upon how tightly and in what manner the drill pipe is stuck. When the drill pipe becomes stuck by balling up while  drilling  in  soft  shale  or  clay,  it  can  often  be loosened  by  circulating  clear  water.  An  upward  strain should be kept on the pipe while circulating the water. When the pipe is stuck by sand or drill cuttings that have accumulated in the hole, circulation should be maintained with the heaviest mud obtainable. When possible, the pipe should be worked. Any movement transmitted through the pipe, however slight, helps dislodge the sand particles into the mud stream that carries them to the surface. When  a  drill  pipe  is  stuck  through  lack  of circulation, there is not much that can be done to recover the entire string of pipe; however, an attempt should be made to pull the pipe with jacks. Sometimes the pipe can be recovered by mixing the proper circulating fluid and circulating it while working the pipe with both the rotating  and  hoisting  mechanisms.  In  some  instances, the  pipe  can  also  be  recovered  by  cutting  it  with  a blasting charge in the bottom of the hole or about where the pipe is stuck. Fishing One of the major problems encountered when well drilling is the recovery of tools lost in the well. Lost tools are recovered by fishing. The most frequent cause of tool loss in rotary drilling results from the drill pipe twisting off. Such “twist offs” usually occur near the lower end of the pipe. They may consist of a simple shearing off from the pipe or of a fracture at a coupling. The accidental dropping of a drill pipe into a hole also calls  for  fishing.  Among  less  common  accidents requiring fishing is the dropping of tools, such as slips or  wrenches,  into  the  hole.  When  a  break  occurs, remember  the  exact  depth  of  the  break.  This  helps  in locating the tops of the tools and coupling to them with a fishing tool. Recovery of lost drill pipes depends upon whether the driller can set the tool down on top of the pipes and connect to them. Some of the more common fishing tools are the circulating-slip  overshot,   the die  overshot,  and  the tapered fishing tap  (fig.  9-13). The circulating-slip  overshot,   as implied by its name, provides circulation through the lost pipe to assist removal when fishing. This tool is similar to the die overshot in its action but provides a watertight coupling between  the  drill  pipes. Figure 9-13.-Tap and overshot fishing tools. The  die   overshot   is   a   long-tapered   die   of heat-treated steel. When fitted over the lost drill pipe and rotated, the die overshot, like the fishing tap, also cuts its own threads. The tapered thread is fluted to permit the escape of metal cut by the threads. The upper end of the die has a thread to fit the drill pipe. The die is hollow but, as is also true of the tap die, circulation cannot be completed to the bottom of the hole through the lost pipes because the flutes allow the fluid to escape. The tapered fishing tap, as its name implies, is a fluted tapered tap made of a heat-treated steel. Its action is similar to that of a machine tap, as it cuts its own threads when rotated, and thus grips the lost drill pipe. REMEMBER: In many shallow wells, it is more economical to abandon the hole than it is to fish for the lost  tools. WELL  DEVELOPMENT  AND COMPLETION Once an aquifer has been tapped by the drilled hole, the important and essential phase of completion and development  must  be  accomplished  in  order  to  assure maximum   yield   under   sanitary   conditions. Development  and  completion  of  a  well  includes 1. 2. 3. setting the casing and screens, removal of the drilling fluid, and stabilization  of  the  aquifer  by  removal  of  a predetermined  percentage  of  the  fines,  grouting, and  sterilization  of  the  well. 9-15