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It behooves the operator to complete his well in the shortest time possible; therefore, the modern method is to seal off the gas sand and continue drilling without further delay.
The use of mud-laden fluid in killing a gas well is too well known to require a description here, but it may be interesting to know that the "lubricator" method of introducing mud into a gas well presented some practical difficulties in operation and was attended with some hazard.
The large gate valves which were used became difficult to operate, partly because they were not designed to operate in mud.
-- Anchor Bolts
By using the control casing head already on the well, these difficulties and the expense of buying and the loss of time in securing special gate valves are avoided.
On top of the control casing head are set one or more joints of any size casing available (two joints of 10-in. casing are my own preference). To the top of the casing extension thus provided, a 2-in. pipe line is connected and brought down the outside of the extension to within about 4 ft. of the floor, the end being fitted with a valve or stop cock (Fig. 7).
From the side outlet of the control casing head a 2- or 3-in. con
nection is made to the pump discharge. This line should be provided with a check valve and a stop cock.
All fittings should be of suitable strength, and as the control casing head is designed for a safe load of 1,800 lb. per square inch all other fittings should be selected from extra heavy stock.
The 2-in. down pipe from the top of the extension should be securely clamped to the extension, and the valve-controlled outlet should be turned in a direction away from the operator.
These fittings are all made while the well is shut in. The pump is then started and mud-laden fluid pumped into the extension chamber until it is full, as indicated by mud showing at the outlet of the blow-off pipe. This outlet is then closed and the valve in the casing head opened permitting the mud to pass into the well. As soon as the extension chamber has emptied, the valve in the casing head is again closed and the outlet valve on the down pipe opened. This operation is repeated until the well is filled and the gas killed.
The advantage of this arrangement lies in the fact that everything is controlled from the derrick floor and no extra help is required. Also time is saved, since the pump will start delivering mud into the extension chamber as soon as the gas pressure is reduced, and, further, it is possible to pump directly into the well without any change of fittings.
Control Head on Flowing Well Reduces Oil Loss and Fire Hazard
With the old method of closing in a flowing well, a flat top was set in the old-style casing head several inches above the side outlet. The column of oil would strike this flat top at high velocity and be broken up into a fine spray, which, upon mixing with the gas, would appear as a blue 'smoke" over the flow tank. This spray would float in the air for a considerable distance, wasting a large amount of oil and covering the surrounding trees and grasses with an inflammable oil. It would also settle in so-called “gas pockets" along the road, frequently becoming ignited by passing automobiles, with attendant loss of life and property.
As previously mentioned, the curved form of the valve in the control casing head gradually deflects the current of oil into the flow line. Therefore, the oil is not broken up into a spray, more good oil is put into the tank, and the fire hazard is reduced.
The Control Casing Head Now Largely Used
The control casing head fills a want that has been long felt and is rapidly being adopted as standard equipment in the drilling of wells for petroleum and natural gas.
At present (September, 1915) approximately 1,000 control casing heads are in use, and, although a great variety of conditions has been encountered in drilling wells, ranging from dry holes to oil wells producing 12,000 bbl. a day, and gas wells having a rock pressure of 1,150 lb. per square inch and volumes in excess of 40,000,000 cu. ft. per day, there has not been a single failure of the head to safeguard life and property, and not one well has burned or become unmanageable.
(SUBJECT TO REVISION
DISCUSSION OF THIS PAPER IS INVITED. It should preferably be presented in person at the New York meeting, February, 1916, when an abstract of the paper will be read. If this is impossible, then discussion in writing may be sent to the Editor, American Institute of Mining Engineers, 29 West 39th Street, New York, N. Y., for presentation by the Secretary or other representative of its author. Unless special arrangement is made, the discussion of this paper will close Apr. 1, 1916. Any discussion offered thereafter should preferably be in the form of a new paper.
The idea of economical production is usually associated with large operations, tonnages, and mines, with even larger capital behind them. Nevertheless many small mines operate in the shadow of large competitors and make a good showing on the capital invested despite larger overhead expenses.
For the purpose of this discussion I will divide the cost of production into classes, and specify opposite each the approximate percentage expended thereon:
1. Labor, including miners and company men; 60 to 75 per cent.
2. Development, including all necessary yardage, room turning, crosscuts, etc.; 7 to 12 per cent.
3. Deadwork, covering payment to miners for handling falls, drawslate, or faults, rock work, water, and in general, all nonproductive labor; 3 to 7 per cent.
4. Supplies: mine timbers, oil, brattice material, lumber, cement, and repairs to equipment; 2 to 6 per cent.
5. Expense: management, selling, office, taxes, etc.; 1 to 5 per cent. 6. Depreciation of coal reserves and royalties; 6 to 10 per cent.
7. Depreciation of equipment and interest on capital invested; 1 to 3
8. Fuel; 22 to 112 per cent.
The labor cost for a small mine is relatively much lower than for a large mine, particularly the sum paid to company men. Idle-pay expense is cut to a minimum; the labor item being larger than all the others together, a saving in labor makes a decided showing on the total cost.
The development charges in small and large mines are about the same. There should be a small showing on the deadwork item in favor of the small mine. The unit cost for supplies is usually small in the small mine. The operator of the small mine finds, owing to a limited tonnage, that the expenses of management, selling, etc., are abnormally high. The item, depreciation of coal reserves and royalties, is usually about
* Mining and Metallurgical Engineer.