FISHING TOOLS AND METHODS.
Unlike many branches of engineering in which the time oc cupied in the various stages of the work can be closely estimated beforehand, the drilling of wells may be delayed by many condi tions that could not have been foreseen. The most vexatious, as well as hazardous of these are occurrences that lead to 'fishing jobs' for the recovery of tools or casing lost in the hole. Such problems may meet with prompt success or may drag along over a long period, for the units of time necessary for many drilling and fishing operations are often days instead of hours, and in this work, as with the original nimrod, Isaak Walton, patience never ceases to be a virtue.
While the loss of tools is accepted as a logical hazard that is bound to occur with greater or less frequency in such work, yet the care and attention to details that finds its reward in all en gineering enterprises are especially valuable traits in this occupa tion, and frequent examination of equipment is unquestionably the greatest single factor in lessening the number of these diffi culties. To this end the drilling and sand-lines should be watched carefully for signs of weakness or unusual wear, drilling tools should be scrutinized for incipient cracks, especially at welds, and no tools or equipment run into the hole unless, as far as can be detected, they are in perfect condition.
Equally important are the steps that may be taken in anticipa tion of the inevitable fishing job, such as calipering the diameters of the different parts of each tool, the internal and external diameters of bailers, etc. Such information may be readily ob tained and noted in the casing tally-book, and when needed at all, is likely to be of the greatest importance and assistance.
Fishing for Lost Tools. It would be impossible to describe all the fishing tools that find use in drilling operations. Many are made for some particular purpose or use in a well where peculiar conditions exist, and when that work is finished they are discarded or remodeled into something else, and heard of no more. Others find a wider application and more general use and so new types of tools and adaptations of old ones are being constantly intro duced. For this reason this chapter will attempt, not to give a
complete summary of all fishing tools, but rather a review of the more common accidents, with the principles of remedial measures and their applications.
Tools for fishing are run in and out of the hole either on the drilling-line or on tubing. In either case they are attached, as is the bit when drilling, to a string of tools that differs from the ordinary drill ing string only in the fact that the stem is placed above the jars instead of below, and the jars (Fig. 167) used have a longer stroke than have the com mon drilling jars. Both changes are made for the purpose of being able to deliver a more powerful blow on the up-stroke of the walking-beam, known as 'jarring,' when an ordinary pull with the drilling line will not dislodge and loosen whatever has been caught with the fishing tool.
A useful accessory, when there is some doubt as to the position or size of the material lost in the hole, and a question as to the proper tool to run for it, is the 'impression-block.' This is a round piece of wood, about 2 ft. long, of such diameter that it travels easily inside the or hole, and • is made concave at the lower end. A few nails pro ject from the concavity, serving to hold in place a mass of fairly soft soap, so that when the block is lowered in the hole, either on the bottom of a bailer or attached by a pin to the bottom of the jars, until it is stopped by an obstruction and then pulled out, the indentations in the soap supply a fairly intelligi ble record of what must be grasped by the fishing tool.
The fundamental principle on which is based the majority of tools for fishing is that of running down, either on the outside or the inside of what is to be recovered, a device containing one or more obliquely-sliding plates with milled or tooth edges, so placed that when the fishing tool is situated beside the lost tool and then pulled up, these edged plates, known as 'slips,' en gage with the lost tool and cling to it while being pulled out (Fig. 168). This principle is applied widely in a great variety of fishing tools for re covering lost tools, rotary drill-stems and for dislodging frozen casing.