BACKGROUND OF THE INVENTION
Field of the Invention
The field of art to which my invention pertains is that of a long-stroke piston type of oil well pump which eliminates prior excessively high, expensive, and obstructive supporting structures without any sacrifice in efficiency.
Particular features of my invention include the following:
1. The direct entry of a flexible pumping member into the well tubing through the utilization of a traveling sealing member and a sealing tube inserted inside the well tubing, thereby eliminating the need for a tall polished rod when the pumping stroke is long.
2. The placement of counterbalance means below ground throughout the period of effective use.
3. The location of the sheave or stroking wheel near ground level enabling the gear reducer to be attached directly or with chain or gear drive to the shaft of the stroking wheel or sheave, being therefore without need for long power transmission cables, pulleys or cogs either to or from said stroking wheel, or for unduly tall structures to support the same.
Description of the Art
An old type of apparatus for lifting a liquid such as oil or water from the bottom of a deep well is a piston which is operatively connected by a string of sucker rods or a cable and a polish rod to a source of vertically reciprocating power at the surface.
One conventional but limited and clumsy surface arrangement which serves to convert continuous rotational motion from a rotary prime mover into reciprocating motion for pumping utilizes a crank, pitman arm and walking beam.
A better solution than a walking beam to the problem of providing a reciprocating power source is to wind a wire rope or a chain around a drum or sheave of fixed diameter, attach a counterweight by a second line, and use either a reversing motor or a motor with a reversing clutch to reverse the direction of rotation at regular intervals. However, the drum or sheave is generally required to be mounted in a high tower or derrick.
The wellhead also conventionally carries a raised fixed stuffing box, through which the polish rod projects upwardly to a considerable height above ground level when the pumping string is at the highest point of its stroke. In periods when the pump is not operating, the exposed exterior of the polish rod is subject to rapid corrosion in most environments.
Perhaps the greatest disadvantage of the two latter arrangements is that they necessitate a very heavy and expensive steel skeleton framework or derrick structure which is strong and rigid enough to be able to support rotating elevated drums, reels, or sheaves, and also is high enough to protect and accommodate the necessary ranges of vertical movement of a polish rod, reciprocating cables, and a heavy counterweight, during their respective strokes. The longer are said stroking motions, the higher and more costly normally is the framework. At some locations, such a framework may actually be high enough to constitute a serious hazard to low-flying airplanes or helicopters. The great weight of the prime mover and gear reducer must usually be kept at ground level, from whence the power is conventionally transmitted to the reels through a long drive cable or other like connecting means. Such latter means are obviously apt to be wasteful of power.
DESCRIPTION OF THE DRAWINGS
In the annexed drawings:
FIG. 1 is a side elevational view of a preferred embodiment of my invention;
FIG. 2 is a top plan view of said embodiment; and
FIG. 3 is an enlarged side elevational view, partially in section, of the traveling stuffing box and seal tube portion of the same embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings in detail, in a preferred embodiment of my invention, a portable platform or skid base 10 is offset on the ground 11 a suitable distance from a wellhead 12 from which the oil or other liquid is to be pumped. Upon said skid base 10 is mounted a suitable prime mover 13, a speed reducer 14, and a low upright supporting frame 15. Said frame 15 may consist of a pair of parallel-spaced A-frames 16 having aligned bearings 17 wherein is journaled a large horizontal shaft 18. On said shaft 18 are mounted a driven sprocket 19 and a stroking wheel or sheave 20, both being positioned between the bearings 17.
In helical grooves (not shown) peripherally encircling said sheave 20 are respectively wrapped in opposite directions a counterweight cable 21 and a pumping cable 22. The inner ends of these cables are suitably anchored in place on said sheave 20. Depending upon the actual circumference of the sheave 20 and the length of pumping stroke desired, a single turn of the cable 22 around the sheave or wheel 20 can be sufficient, although more grooves and turns of the cable can obviously be added to create a longer stroke. The counterweight cable 21, being wound in the opposite direction on the sheave 20, supplies a countervailing force to the action of the pumping cable 22, as the outer end of the cable 21 holds in suspension a plurality of individually adjustable and removable counterweight members such as the metal plates or discs 23. Said latter members 23 will descend into a suitably lined vertical underground pit 24 which is of adequate depth for clearance at the bottom end of the stroke of the counterweight cable 21, but not too deep to hinder recovery in case of cable breakage.
A suitable reversible drive for the shaft 18 which actuates the pumping cable 22 includes an appropriate motor serving as the prime mover 13, the output shaft 25 of which is operatively connected as by belt means 26 to the input shaft 27 of the speed reducer 14. The output shaft 28 of said speed reducer 14 is similarly connected as by chain 29 to the sprocket 19 on the outer end of the shaft 18. A synchronous motor can operate in either direction, depending on which way an initial torque is applied, but a unidirectional type of motor with a reversing clutch can obviously also be used in its place. A control box 30 including switches (not shown) for the prime mover 13 may conveniently be mounted on one of the A-frames 16 adjacent to the sheave 19. For increased portability, the skid base 10 may also optionally be provided with a plurality of vertically adjustable casters or rollers 31. It would also be possible to provide the A-frame which supports the stroking wheel with pivotable legs to provide wellhead clearance.
Seated upon the top of a regular oil well casing 32 is a short upright tubular head member 33 having a circumferential inner flange 34 which together with the polished pipe 35 divides said head member into an upper chamber 36 and a lower chamber 37. Upon the upper chamber 36 is secured a flat cap member 38 supporting a fixed stuffing box 39 which creates a fluidtight top seal through which descends the pumping cable 22. Said upper chamber 36 also includes discharge outlet 40 to drain fluid which leaks by the traveling stuffing box and collects above its packing element. The lower chamber 37 contains an oil discharge outlet 41. The oil and associated fluids will pass between the polished pipes and the tubing and be discharged from this outlet 41.
The interiorly polished pipe 35 has its upper end formed horizontally outward into a radially extending lip 42 which is sealed to the flange 34 by a threaded bushing 43 and is arranged to project downwardly and concentrically in spaced relation within the tubing 32 for a distance somewhat greater than the pumping stroke. A traveling stuffing box 44 carrying a plurality of packing discs 45 of rubber or fibrous material, or a close-fitting metal plunger or a combination of metal plunger and packing material, is positioned in fluidtight relation within said polished pipe 35, and is interposed vertically and secured by clamping means between the lower end of the cable 22 and the upper end of a string of sucker rods 46 or like connecting means. This packing element can also be slipped over a continuous cable when such cable is used as a pumping means, with suitable clamp to rigidly attach packing element to the cable. The sucker rods 46 or cable will be understood as extending downwardly inside the tubing 32 to the pump piston or plunger (not shown), which is near the bottom of the well inside the well tubing. Such tubing is suspended from a casing head 47 which is attached to the well casing 48 at the top of the well. The spaced concentric polished inner pipe 35, however, need not be appreciably longer than the length of the stroke of the traveling stuffing box therein.
In operation, the apparatus described will lift the well fluid until the upstroke is almost complete. The prime mover 13 is then turned off (or a clutch disengaged). The inertia of the moving masses will allow them to coast to a stop and then start to fall back. At this point the prime mover 13 will start in a reverse direction (or a reverse clutch will be engaged), and will start lowering the rods back into the well by lifting the weight of the counterbalance 23. As the pumping string nears the bottom of the wellhole, the prime mover 13 will again be turned off (or declutched), allowing the system to coast to a stop and start to reverse itself. The prime mover 13 will again be started to begin the upstroke.
The well fluid is pumped upwardly in the outer space between the adjacent walls of the casing 32 and the polished pipe 35, and is then discharged from the outlet 41 to a point of storage or transport. Inasmuch as many such fluids include much brine or other substances which are highly corrosive to a pumping cable, the traveling stuffing box 44 excludes such fluids from any direct contact with the cable 22 above said traveling stuffing box 44. Also, if desired, a special preservative or corrosion resistant compound or lubricant can be maintained around the lower end of said cable 22, simply as an added precaution against corrosion.
When the traveling stuffing box 44 wears sufficiently to require repairs or replacement, it can be raised above the upper end of the polished pipe 35, and it can then be easily repaired or replaced.
One of the most important requirements for proper operation of the above-described arrangement is the smooth reversal of the system. Proper setting of the reversing switches (or clutches) is particularly important. This allows the inertia of the moving masses acting against opposite well load conditions to cause the system to coast to a stop and initiate the reversal. A super high slip (30-40 percent slip) electric motor which has limited torque could be used effectively as the prime mover 13 in order to control acceleration values at the points of stroke reversal.