Pumps – Motor driven – Fluid motor
Patent
1986-07-18
1988-02-23
Smith, Leonard E.
Pumps
Motor driven
Fluid motor
91216R, 91216A, 91216B, F04B 4708
Patent
active
047267437
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates generally to methods and means for pumping oil and water from deep wells and, more particularly, to the use of reciprocating pumps powered by pressurized fluids, such as gas, oil or water. Although fluid power has long been used to power such pumps, severe difficulties still exist in the pumps now available, such as sand cutting, sand fouling, vapor locking, excessive use of energy, excessive downtime and excessive replacement of downhole tubing and other equipment.
Although the use of sucker rods to operate a downhole reciprocating pump is the oldest and most wide spread method, the well known high first cost and endless maintenance problems inherent in sucker rod systems have almost become accepted by many operators as inevitable which, unfortunately, drives up the cost of oil and gas, and many "crooked holes" cannot be pumped at all with the use of sucker rods. The practice of "gaslifting" liquids from wells by injecting pressurized gas into a column of liquid within a tubing is well known to be an inefficient system when compressors are required to compress the gas before injection, and, it cannot be used at all in most deep wells of today.
Downhole hydraulically-driven pumps have been used since 1935, but are used in less than 1% of pumping wells today because of excessive maintenance. Typical recommendations for such devices are to change the pump every two months.
Therefore, particularly with regard to such wells as offshore wells, which are generally both deep and directionally drilled, when the pressure of their producing formation declines such that they will no longer flow on their own, a more reliable and efficient method and means for pumping is needed by the industry to gain many millions of barrels of oil and billions of cubic feet of gas, as the present invention provides.
BACKGROUND ART
U.S. Pat. Nos. 2,362,777 and 3,123,007 disclose early systems for hydraulically driving a reciprocating well pump, but neither have bearing on the present invention. Many similar patents exist, some having fluid motors for attachment to conventional pumps or to operate a string of sucker rods, which, in turn, operate a conventional downhole pump.
Coberly U.S. Pat. No. 2,952,212 operates by co-mingling spent power fluid with produced liquid from the well, which requires separation and purification fo the power fluid before recirculation to the downhole pump. A later Coberly patent, U.S. Pat. No. 3,005,414, employs a power fluid string and a separate string to return spent power fluid as well as a production string to convey produced liquid to the wellhead.
Of more particular interest are U.S. Pat. Nos. Hammelmann 3,307,484; Garraway 1,448,486 and Sargent 2,748,712; which generally are of the same type as the present invention. However, all three disclose torturous paths or conduits through which hydraulic fluid must flow in order to operate the pump. The conduits, as depicted, are of small cross section relative to the pumps outer diameter and the conduits also have many changes in direction. Such a device can be jammed by a very minor amount of solid, such as will be found in any hydraulic fluid used to operate a downhole well pump, since the fluid cannot be kept as clean as fluid can be kept in a small surface system.
The severest limitation for a downhole device is the limitation of its outer diameter. Such convenient arrangements as outlet pipe 15 depicted in Garraway, or as outlet pipe 4 depicted in Hammelmann, or side outlets 78a as depicted in Sargent, cannot be included in a downhole pump without reducing the abovementioned small flow paths even further, if the pump is to pass downward within typical well tubings.
The small size of the flow paths is even more important when you consider the great increase in pressure drop that is caused by reducing the cross-sectional flow area. Well known laws of hydraulics tell us that given flow rate of a given fluid will produce a pressure drop per unit length of pipe, in direct proportion to the diameter of the flow pat
REFERENCES:
patent: 2305388 (1942-12-01), Price et al.
patent: 2805625 (1957-09-01), Crow
patent: 2862448 (1958-12-01), Belding
patent: 3152016 (1964-10-01), Drushella
patent: 3522996 (1970-08-01), Bentley et al.
patent: 4118154 (1978-10-01), Roeder
patent: 4369022 (1983-01-01), Roeder
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