depending upon how tightly and in what manner the drillpipe is stuck.When the drill pipe becomes stuck by balling upwhile drilling in soft shale or clay, it can often beloosened by circulating clear water. An upward strainshould be kept on the pipe while circulating the water.When the pipe is stuck by sand or drill cuttings thathave accumulated in the hole, circulation should bemaintained with the heaviest mud obtainable. Whenpossible, the pipe should be worked. Any movementtransmitted through the pipe, however slight, helpsdislodge the sand particles into the mud stream thatcarries them to the surface.When a drill pipe is stuck through lack ofcirculation, there is not much that can be done to recoverthe entire string of pipe; however, an attempt should bemade to pull the pipe with jacks. Sometimes the pipe canbe recovered by mixing the proper circulating fluid andcirculating it while working the pipe with both therotating and hoisting mechanisms. In some instances,the pipe can also be recovered by cutting it with ablasting charge in the bottom of the hole or about wherethe pipe is stuck.FishingOne of the major problems encountered when welldrilling is the recovery of tools lost in the well. Lost toolsare recovered by fishing. The most frequent cause oftool loss in rotary drilling results from the drill pipetwisting off. Such “twist offs” usually occur near thelower end of the pipe. They may consist of a simpleshearing off from the pipe or of a fracture at a coupling.The accidental dropping of a drill pipe into a hole alsocalls for fishing. Among less common accidentsrequiring fishing is the dropping of tools, such as slipsor wrenches, into the hole. When a break occurs,remember the exact depth of the break. This helps inlocating the tops of the tools and coupling to them witha fishing tool. Recovery of lost drill pipes depends uponwhether the driller can set the tool down on top of thepipes and connect to them.Some of the more common fishing tools are thecirculating-slip overshot, the die overshot, and thetapered fishing tap (fig. 9-13).The circulating-slip overshot, as implied by itsname, provides circulation through the lost pipe to assistremoval when fishing. This tool is similar to the dieovershot in its action but provides a watertight couplingbetween the drill pipes.Figure 9-13.-Tap and overshot fishing tools.The die overshot is a long-tapered die ofheat-treated steel. When fitted over the lost drill pipe androtated, the die overshot, like the fishing tap, also cutsits own threads. The tapered thread is fluted to permitthe escape of metal cut by the threads. The upper end ofthe die has a thread to fit the drill pipe. The die is hollowbut, as is also true of the tap die, circulation cannot becompleted to the bottom of the hole through the lostpipes because the flutes allow the fluid to escape.The tapered fishing tap, as its name implies, is afluted tapered tap made of a heat-treated steel. Its actionis similar to that of a machine tap, as it cuts its ownthreads when rotated, and thus grips the lost drillpipe.REMEMBER: In many shallow wells, it is moreeconomical to abandon the hole than it is to fish for thelost tools.WELL DEVELOPMENT ANDCOMPLETIONOnce an aquifer has been tapped by the drilled hole,the important and essential phase of completion anddevelopment must be accomplished in order to assuremaximum yield under sanitary conditions.Development and completion of a well includes1.2.3.setting the casing and screens,removal of the drilling fluid, andstabilization of the aquifer by removal of apredetermined percentage of the fines, grouting,and sterilization of the well.9-15
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