If the casing has not been landed upon a shell, or in a body of shale or clay below the sand, a wooden plug having a wedge at the top should be lowered to bottom and the wedge driven by the tools to expand the plug to the diameter of the casing. After this an iron heaving-plug should be placed on top of the wooden plug to prevent the latter from being dislodged and corning up the hole. The iron heaving-plug (Fig. 105) has four slips which wedge to the side of the casing and keep it in place.
Rotary Method. The use of the rotary is becoming more gen eral in all oil fields, particularly in California, where, until a few years ago, it was considered by many operators a failure. Its recent success is due to improved tools and methods as well as having attracted a better class of drillers, until, at the present time, there is little territory in that State which cannot be successfully drilled with the rotary. While the number of men required (10 to 11) is greater than that for the standard tools and the equipment more expensive, yet the time and casing saved far more than offset any additional labor. The rotary was originally made by the American Well Works and used in N6rth Carolina. The working parts were crude and it met with indifferent success. The first oil-well rotary was used at Corsicana, Texas, and became widely used in the Beaumont field at Spindle Top, Texas. Improvements in rotary machinery have gradually been made until at the present time all the working parts are capable of meeting the severest conditions.
The practical operation consists in rapidly rotating a column of pipe, at the lower end of which is a cutting-bit, the pipe being lowered as drilling progresses and the drillings washed out by the action of a pump. The walls of the hole are 'mudded up' with clay to prevent caving, at the same time causing the pipe to turn more easily, while the mud can be used over again by running it back to the pump-suction. The equipment consists of a turntable, draw works and line-shaft, drill-stem, engine and boiler, two pumps, swivels and hose and the bits besides other special apparatus. A 12 by 12-in, engine is generally installed and transmits power to the line-shaft by sprockets and chains. On the line-shaft is a sprocket by which the draw-works (Figs. 108 and 110) are revolved, the larger pipes having sprockets for a low and high-speed gear. In line with the sprocket wheel on the rotary table is a larger sprocket wheel on the line-shaft, while a chain furnishes the motive power. Two powerful brakes are placed on each side of the drum for control by the driller. The throttle-wheel brakes and clutch are so placed that each can be manipulated by the driller without moving. The turntable (Figs. 106 and 109), consisting of a heavy rotating device running upon steel rollers, controls the drill-stem by grip-rings which are set tip sufficiently tight to turn the pipe without mashing it. A patented drill-stem is now in use which takes the place of the grip-rings. A special head sets in the open space of the table, and the drill-stem, which is 30 ft. long, can be run through it and at the same time rotated by wings which project from the stem into the head. This stem is never lowered below the table, a joint of pipe being installed below it each time instead, so that it always works through the rotary table. This effects a. saving in pipe,
grip-rings being unusually severe on the drill-stem. When pulling or lowering the latter into the hole, a spider is substituted for the special head and slips are used as in the standard-tool drilling. The pumps are 10 by 6 by 12-in. and are so connected as to run singly or doubly. Each is provided with a screen in the discharge-line to prdrent packing or debris from the pit getting into the drill-stem and plugging the bit. Connected with the discharge-line are two 30-ft. lengths of heavy wire-wound hose and when rotating, one is attached to the swivel (Figs. 111 and 112). The latter is screwed into the top cotipling of the drill-stem and has a long bail or link by which the drill-stem can be raised or lowered. Roller bearings are used in the swivel to support the weight of the drill-stem at the same time allowing it to turn around without twisting the lines.
The mud coming from the well is conveyed by a box-ditch running from the outlet around the derrick to the slush pit, where it is again taken up by the pump suction. In some of the deeper fields, a hole 4 by 4 by 10 ft. is excavated under the derrick floor, a joint of 16-in. stove-pipe set into it vertically, and the outside space filled with concrete. This prevents the walls at the surface from caving and provides a good base for anchoring the casing. A heavy 4-sheave block ( Fig. 114) is used for handling both pipe and drill stem tools, the larger sizes weighing 2700 lbs., while a 6-in. casing hook is suspended from it by a heavy 'C' link ( Fig. 115). Nine lines can be threaded on the, deeper wells, five being the usual number at the surface. The fish-tail bit ( Fig. 116) is commonly used, 14 to 15 in. being the usual sizes for starting the well. The ends are dressed with a taper and turned back slightly to form a cutting-edge while the later types have a long shank which tends to ream the hole and keep it straight. Through each side is bored a .34-in, hole, through which the water under pressure enters, strikes bottom and returns between the wall and drill-stem carrying with it the drillings. Other rotary bits for special uses are the chisel-point ( Fig. 117) for drilling past pipe or drilling out wash-rings. The drag-bit (Fig. 118) is similar to the regular fish-tail pattern, except that the cutting edges are reversed so that they drag. This form of bit is used in drilling through hard rock, adamantine being dropped into the well to make the cutting faster. The drag-shoe is also used in the same way, leaving a core to be extracted later. The core-barrel is also made to drill hard formations with about the same result as the drag-shoe, the core being removed in either case by throwing in small pieces of cast iron which wedge between the shoe or barrel and the core, when the latter can be broken off and extracted. Adamantine should be sparingly used and the couplings be kept free from it, else the threads become badly damaged. When possible, adamantine does better work without circulation, as the water washes it away from the bottom. To extract more than 2 ft. of core at a time is dangerous, for breaking it off becomes a difficult matter, the drill-stem often parting in the attempt.