If a well of promise is obtained the next consideration is the shooting of the well. This operation consists in lowering a certain amount of nitro-glycerin in a tin shell with sufficient amount of it to fill up the entire distance opposite the pay streak or sand; it is then exploded by dropping a time fuse or some times by the old fashioned go-devil; the object being to shatter the pay sand, thereby increasing the flow of its contents. The amount of nitro-glycerin put into a well depends upon the thickness of the sand and the diameter of the hole at that point. The attempt is to shoot all of the sand. If water is present in the sand below the oil the shell is so placed that the sand lying above the water is shot, so as to avoid increasing the amount of water as much as possible. When only a few feet of pay sand is found it is sometimes customary to place a "dump-shot" with the regular one, which is done as follows: after the nitro-glycerin shell is in place, another shell filled with nitro-glycerin is lowered, but when reaching the bottom its contents are allowed to escape, "dumped," thereby increasing the amount of shot that might be placed in the hole.
A dolomitic limestone will stand almost any amount of shooting, and many wells, apparently dry, have been made producers by shooting. Soft sands do not show good results from shooting and the loose or unconsolidated sands are not shot at all. 'Wells which produce a large amount of oil naturally should not be shot until they cease to flow. In this way a large amount of oil may be obtained without the danger of the well being ruined by shooting, as shots will work both ways, and although in the majority of cases they bring good results, still, there are many instances where wells have been ruined by shoot ing, as it may have liberated a large amount of water, or sealed off the pay portion of the sand, and it is also possible that the casings may be shot into, either fracturing them and allowing water to come in and drown out the oil, or the casing may be so bent and plugged as to form a bridge which necessitates expensive fishing operations, which if unsuccessful would mean the aban donment of the well. Whether the shooting of a well may be
deferred depends upon the existing conditions; thus if a neigh boring property is producing oil, it will require similar tactics upon the part of the operator to put his well also in condition to prevent the opposing operator from draining the territory with out opposition.
All wells that are non-productive or those that have so declined as to be no longer a commercially valuable producer, should be plugged. The methods of plugging are similar in most fields. Many States require certain methods, and espe cially in a coal-producing State, the plugging requirements are strict, as coal beds are to be protected. In many cases a permit is first to be applied for, and the well plugged in the presence of of an inspector appointed for that purpose. Plugging is desirable, whether enforced by regulations or not, as it will prevent the flooding of the sand from sources outside of it, and keep the rock pressure from declining.
The drilling of wells in a territory where large wells are expected necessitates various controlling devices with which big flows may be checked and property capped or shut in. These devices vary in different localities and there are many good appliances on the market which may be used.