The bit is heated in a forge that burns oil, gas, or coal. When brought to a cherry-red heat, the bit is pulled from the furnace, and swung on the forge, where the driller and toolie attack the dull end with sledge hammers. The main object in dressing bits is to maintain a flare on the edge of the bit, much like the outer edge of a horse's hoof, and at the same time keep the bottom of the bit slightly concave or hollowed. Figure 23, page 72, shows the dressing of a bit by portable steam hammer.
Standard drilling bits crush and smash as well as dig. For this reason a sharp-pointed bit is not desirable. The bit is used until the flare is worn off and the face of the bit becomes flat.
Rotary drilling bits are used until the flares of the fish-tail are worn down nearly to the point where the bit is split. In dressing a rotary bit the remaining stub is drawn out from the shank so that the steel makes a thin beveled edge. Then the new length is split with a splitting chisel, and the halves are now bent or flared in opposite directions, giving the shape of the typi cal fish-tail bit. Dressing bits is hard work and calls for skill in proper heating, correct cutting, and shaping.
Types of Engines Employed in steam engines used belong to the horizontal simple reciprocating type. They are set on a heavy wooden block called the engine block. (See Fig. 24, page 73.) A drive belt passes from a pulley on the engine tu the band wheel. This pulley wheel is balanced by the fly wheel. Weight is added to the fly wheel by circular balance weights that can be bolted to the fly wheel. The gas engines and electric motors work on the same principle.
Drilling engines have dimensions of 11: by 12 in. to 12 by 12 in.
This means a cylinder diameter of 10M to 12 in. and a stroke of 12 in.
Pumping-engines range from 9 by 12 to 10 by 12.
These steam engines range from 15 to 60 hp. The deeper the well the greater the power necessary.
Twin recent improvement in oil-field engines is the twin or duplex engine. Two 9 X 10 twin engines are used in place of one heavy 112 X 12 or 12 X 12 engine. The two engines give a steadier pull than the single engine. In rotary drilling this is less liable to cause "twisting off," which is the result of sudden jerks. Also the engines cannot get "on center." This is a decided advantage in drilling.
Types of boilers used in drilling are of two general types, namely the locomotive and the plain horizontal tubular. The locomotive type (see Fig. 25) is internally fired, while the simple tubular boiler is externally fired. The latter is hung on a frame and the sides are walled as shown in Fig. 26. This type of boiler is in general use in California. Such boilers develop from 20 to 60 hp. for locomotive types and from 35 to 100 hp. for the horizontal tubular types. They have heating surface roughly 12 sq. ft. per horse power, and use from 15 to 20 bbls. of oil per day, on drilling wells, and 2 to 4 bbls. per day for pumping wells.
On producing leases, batteries of three to six boilers are housed under sheet-iron roofs. These boilers produce steam for pumping the wells and sometimes for drilling operations as well. Such batteries have boilers ranging from 60 to 100 hp. There is not always uniformity in such boiler plants. Some plants have Sterling water-tube boil ers, Wilcox boilers, and marine internally-fired water-tube boilers, and also plain horizontal tubular boilers externally fired.
Fuel.—In drilling wells in new districts the fuel used may be cordwood, coal, fuel oil, and some times natural gas, depend ing upon the relative cheapness of the various types of fuel. In drilling near proven fields, fuel oil or natural gas are the main fuels used.
Use of Electricity for Drilling.—The use of electricity in oil-field operations has made re markable changes in some places. There is a distinct saving in fuel by the use of electricity. Where the well is in reach of a power line, there is a big advantage in its use. This is especially the case in hilly or mountainous areas, where the expense of transporting fuel oil, or coal, is very high. In cases, motors also save the hauling of water for steaming purposes. The first motors were not considered suited to oil-field practice, as they lacked elasticity, but they have been greatly improved, until now such motors are well liked by the drillers.
The saving in the use of fuel is marked. On a "wildcat" well in California the fuel bill for oil was $1200 per month. The installation of a motor cut the power cost to $300, a saving in fuel alone of $900 per month.