Derrick

A derrick is necessary for lifting tools and pipe in and out of the hole. As maximum length of single joint of pipe will exceed 40 feet slightly, the derrick not have to be as high as average rotary derrick. Three hoisting reels distinguish cable tool machine. The bull wheel handles the drilling tools going in and out of hole. The calf wheel is used for hoisting and running of casing. The sand reel car the small line on which the bailer and, later, the swab is run. An up and down mote is imparted to the frilling tools by the walking beam or by a spudding arm. The walking beam, used on the standard rig, operates like a pump jack dropping drilling string attached to the end over the hole. The spudding arm operates pushing a grooved sheave against the fixed line of the drilling string for rising in hole and then drooping by suddenly releasing the line. The bit is screwed into a hear stem to impart additional weight for cutting. Immediately above this, in the drilling string, are the jars, which permit flexibility in the string and aid in giving a from striking motion. The jars are similar to two huge chain links. The arrangement permits blows to be struck upward so that a stuck bit may be retrieved. The jars may be weighted from above by a sinker, which is a long, cylindrical joint of solid met. The complete sting of drilling tools is surmounted by a socket to which is attached the drilling line.

Secondary recovery

The amount of oil originally in the reservoir which is not recoverable by natural recover mechanisms and by ordinary pumping methods is considerable. It is estimated the amount ranges from 15 to 75 %, depending upon the type of natural recovery mechanism and other factors. It is possible to recover a large part of the oil in the reservoir by secondary recovery methods. Secondary recovery is the recovery of oil and gas by any method, such as artificial flowing or pumping that may be employed through the joint use of two or more wells. Liquids or gases are injected into the common reservoir through one or more injection wells, and the oil and gas are produced through other wells by flowing or pumping. The secondary recovery method most commonly employed at the present time is water flooding.

Water flooding

Water flooding is the most efficient method of secondary recovery if structural and sand conditions are favorable. The secondary source of energy is water under pressure. The water, which is injected into the reservoir under pressure, operates essentially as a flushing agent pushing the oil ahead of it. Water flooding operations have been very successful in certain fields. The structure of the areas should be gently dipping and without faults. Permeability should be uniform and the reservoir rock continuous. Experiments have shown that that a residual oil content of from 15 to 25% will remain in the reservoir sand after is has been wetted by water, as in a water flooding operation. It is possible therefore to determine by a through study of cores the approximate amount of oil which can be recovered by water, flooding. An additional recovery as large as that obtained during natural flow is possible if the connate water saturations are high.