After carefully studying conditions, a plan of procedure is out lined. In some wells cementing may be necessary, new casing points in others, or total abandonment may be advocated for some wells.
Once the trouble has been ascertained the practical field man steps in and proceeds to doctor the wells in accordance with the general remedial plan.
The various methods of combating water troubles are: 1. To put the walking beam in the third hole, thus gaining a longer pump stroke, and speeding up the wells to pump as fast as possible.
2. To install air compressors and use air lifts for handling the water.
3. To abandon the hole.
4. To shut off the water: (a) by wooden or lead plugs; (b) by packers; (c) by cementing; (d) by mudding off the water.
1. Where wells are pumped rapidly, rod and tubing troubles follow quickly. " Crystallized " rods result from the fast pumping and breakages are more frequent. Shutdowns due to such causes sometimes average as high as 40 per cent of the pumping time. When wells are shut down production is lost, due to loss of time. When again on the beam it is noticed that the wells may pump water for several days before making any oil.
Another loss is that of the casing-head gash line content. Vacuum pumps will not work with any efficiency on water-flooded wells, especially when the oil sand is submerged.
The high cost of pumping small wells in creased so rapidly that in the North Cushing, Oklahoma, pool wells were abandoned when making a few barrels of oil because the lifting expense was greater than the value of the oil.
2. The pumping of water by compressed air is an expensive system, with the other remedies available. The compressed air system of pump ing water will not be described here as its use is unnecessary with present methods of handling water troubles.
3. There are occasions when water has flooded the sands completely; when knowledge of the sands in the well is so incom plete; when the hole is full of tools which cannot be fished out, that abandonment of the hole is justified.
Wooden and Lead Plugs.—" Bottom water"—that in the bot tom of a sand—may be shut off by using wooden or lead plugs (see Fig. 77, page 182).
These plugs are let down to the bottom of the hole. A hole drilled into the middle of the plug holds a mandrel or round wedge. When this is driven down the wood, or lead as the case may be, is expanded and fills the drill hole. Some fine mud placed on top of this may assist in shutting off the water. This method fills a temporary need, but is not the most efficient.
Packers.—Before cementing methods were so well developed, packers were much used to shut off water. In the Mid-Continent and Eastern fields, where cementing methods are not so well recognized, they are still greatly in favor. In hard formations, where limestone or hard shale beds are found, packers may lie used to advantage.
Packers are placed on the tubing or on the casing, and shut off the water. They are of two main types: (A) Wall packers.
(B) Bottom packers.
Wall packers are of several types. The device shown in Fig. 78, page 183, is placed between joints of casing and let down on the casing string to a point above the oil sand where a hard limestone or shale bed is found. This packer consists of two cylinders, which partly telescope. A rubber cylinder is placed on the out side of the upper cylinder. When the casing is turned a catch is released and the upper cylinder, forced downward by the weight of the casing, tends to telescope into the lower cylinder. This expands the rubber against the wall of the hole and makes a tight joint. The casing is then turned which sets the packer tight against the wall of the hole. Any water above the packer is excluded from the hole. Where much open hole is left, the packer may be set on a string of tubing instead of casing.
Another type of packer, called the "boot-leg," shown in Fig. 79, has much the same action. The "boot-leg," how ever, is a homemade affair, of canvas or leather riveted together, and is conical in shape. The upper part flares out. This packer is set below the water sand. Mud or soft shale cuttings are put in the hole above the packer and settle in the "boot-leg." This causes the "boot-leg" to ex pand, and makes a tight joint with the wall of the hole.