CHAPTER XII FINISHING THE WELL Finishing and Shutting in Oil Wells, Pumping Equipment, Setting Screens and Liners, Washing Wells, Shutting in Gas Wells FINISHING AND SHUTTING IN OIL WELLS WHERE FORMATIONS STAND UP All wells should be drilled in slowly and carefully. If the producing formation is known to contain no water, it may be safe to drill out each screw before pulling out and bailing and examining the sand. In a sand carrying bottom water or in a test well it is best to withdraw the tools and bail out every one to three feet. At the first sign of bottom water, drilling should be stopped. When conditions permit it is good practice to drill ten to fifty feet of pocket, or leg, below the producing formation. This serves the dual purpose of a receptacle in which the oil and also floating sand and cavings may collect, and prevents the latter from filling in and covering the producing formation. The top joint of casing which usually is belled, should be removed and a casing nipple and casing head substituted before drilling in, so that in the event of a sudden flow of oil or gas the operator may be prepared to connect the well to a tank or to close in the gas. Occasionally a well is drilled into a strong flow of oil and, if the operator is unprepared, much oil may be lost. A device known as the Control Casing Head has come into general use in Mid-continent territory which prevents this waste. It really is a casing head and gate valve combined (see Fig. 201) and is so designed that the well may be shut in entirely, or permitted to flow in such reduced volume that the production can be cared for without loss or waste. A notch in the valve receives and closes around the drilling line, making a tight joint. When drilling in wells in a partially developed field where gusher wells are not common, but where the well might flow, one of the several types of oil saver should be used. The oil saver (Fig. 202) is a device that fits in the top of the casing head with a plunger in which the drilling cable is confined, or a stuffing box through which it may pass, thus partially, at least, closing in the well while drilling progresses. SHUTTING IN AN OIL WELL Where the producing formation stands up a flowing well may be shut in the casing by means of a gate valve or by simply closing the top of the casing head with a solid top or a plug and permitting the well to flow through the side outlets, to which lead lines to the tank, equipped with stop cocks, are connected. When the pressure and volume have diminished so the well will no longer flow through the casing, tubing, usually 2 inches in diameter, with a packer at the bottom is put in. The oil, thus confined to the smaller tubing, may continue to flow. When the well will no longer flow through the tubing, it must be put to pumping. Swabbing and agitating are sometimes effective in causing wells to resume flowing. The swab (Fig. 203) is a device fitted with a check valve and a Fig. 203 rubber that approximates the diameter of the casing. It is operated on drilling tools and, as its name implies, is run to the bottom of the well and withdrawn, swabbing out the oil in the well and creating a suction that may cause it to flow for a short time. Agitating is done by running the drilling tools or lowering a polished rod or other weight on the sand line and raising and lowering it, which may cause the well to flow. In California operators sometimes raise and lower the oil string of casing as a means of agitating. In the Mid-continent fields the "squibbing," so called, of wells that have ceased flowing is often done. This consists of shooting the well with a small quantity of nitro-glycerin when it stops flowing and repeating the process until the well fails to respond further, when it is put to pumping. The pumping of deep wells whose production is not settled is usually done with a separate power unit for each well, usually a gas engine. Shallow wells and sometimes deep wells whose production is small are connected to a central power plant, operated with a gas engine. A pumping jack is placed over each well and these are operated by pull rods radiating from the power to the several wells, refer to Fig. 204. Fig. 204.-Diagram of Central Power Plant for Pumping a Group of Wells, showing Eccentric Power, Gas Engine, Pull Rods and Pumping Jack at each well. Adjuster Board PUMPING EQUIPMENT Crosshead Walking Beam Grip Pipe Sgl Grip Adjuster Stuffing Box Lead Line Casing Head Derrick Floor Valve Rod Upper Valve Working Barrel Lower Valve A pumping outfit (Fig. 205) for a well to be pumped by means of the walking beam of the derrick consists of the following: Adjuster, fitting in the temper screw slot of the beam, used to grip and to adjust the length of stroke of the polished rod. Adjuster board used as a top bearing for the cross-head of the adjuster. Tee bolt to bolt the adjuster board to the beam. Grip pipe to connect the adjuster grip with the cross-head. Polished rod, or plunger, connecting between adjuster and sucker rods. Stuffing box, used at top of well as a gland Perforated Pipe through which polished Or rod works. |