The Sucker Rod Pumping System

The sucker rod pumping system consists of a prime mover, a pumping unit, a polished rod with a stuffing box to seal off the pumped fluid pressure at the surface of the well, and a sucker rod string to transmit the reciprocating movement from the pumping unit to the sucker rod pump. The pumping unit is the mechanism that converts the rotary movement of the prime mover to the reciprocating movement needed to power the sucker rod pump. The sucker rod string consists of individual sucker rods of 25- or 30-ft (7.6- or 9.1-m) lengths that are connected with couplings when they are lowered into the well. This total length of rods connects the surface polished rod to the pump at the bottom and is called the sucker rod string. The complete sucker rod pumping system is illustrated in Figure 1.

The operation of a sucker rod pump is illustrated in Figure 2. The pump is submerged in fluid near the bottom of the oil well. As the sucker rod string and plunger make an upstroke, fluid from the well bore flows past the standing valve into the pump barrel. Also on this upstroke, the traveling valve is closed and the fluid above the plunger is pumped up the annulus between the sucker rod string and the tubing string. On the downstroke, the traveling valve is open and the standing valve is closed. The fluid in the pumping chamber between the traveling valve and standing valve is displaced into the annulus between the tubing and the sucker rod string above the plunger. The fluid in the annulus is lifted toward the surface only on the upstroke.

The Sucker Rod Pump The principal parts of the sucker rod pump are the barrel, plunger, traveling valve, and standing valve. These are seen in a cutaway section in Figure 3. In shallow wells relatively free of sand, soft-packed plungers are frequently used. These have a number of fabric rings or cups that are expanded by the pumping pressure to a close fit with the barrel. In deep wells or in hard-to-pump shallow wells, the precision-fit metal barrel and plunger as shown in Figure 3 are used. The most common precision barrel is made from steel tubing with a case-hardened or induction-hardened inside wear surface. The inside diameter of the barrel is honed to the nominal bore size with a tolerance of ±0.001 in (0.025 mm). Premium barrels are chrome-plated on the inside diameter to a thickness of 0.003 in (0.076 mm) per side. Material for these barrels may be carbon or stainless steel, brass or Monel. The brass or Monel tubes are used when hydrogen sulfide, carbon dioxide, and brine mixed with produced fluid create an extremely corrosive condition. More common barrel lengths range from 5 to 24 ft (1.5 to 7.3 m), but longer lengths are available for use with very long-stroke surface units.

There are several kinds of plungers. A chrome-plated one-piece plunger or a plunger made of hard cast alloy iron sections assembled over a steel plunger tube is usually used with the precision hardened steel barrel. A plunger that is hard-faced with a nickel-based spray metal material is usually used with the chrome-lined barrel, although the cast plunger can also be used there. Plungers range from 2 to 6 ft (0.6 to 1.8 m) in length, depending on the depth of the well. These plungers are all ground to a precision tolerance of + 0.0000, -0.0005 in ( + 0.000, -0.013 mm). The diametral fit between the inside of the barrel and the outside of the plunger ranges from 0.002 to 0.005 in (0.05 to 0.13 mm), depending on the quality of the well fluid and the diameter and length of the plunger.

The traveling valve and standing valve of the pump are simple ball-and-seat check valves. Type 440 hardened stainless steel materials are the most common, but in corrosive wells, a cobalt-chromium-tungsten alloy is frequently used, and in very abrasive wells tungsten carbide seats and balls are used.

Sucker Rods Sucker rods are manufactured from carbon or low-alloy steel. Table 1 lists the properties of the grades of rod used most frequently. Most sucker rods are manufactured in 25-ft (7.62-m) lengths, but a few areas use 30-ft (9.14-m) lengths. Both ends of the rods are upset* and externally threaded (Figure 4). The upset ends also have a square for wrenching. Internally threaded couplings are used for connecting rods to make the

*In oil field terminology, an upset is an enlarged portion formed on the end of the rod by forging. This allows for a joint that is stronger than the body of the rod.

FIGURE 1 Sucker rod pumping system: (1) prime mover, (2) gear reducer (3) crank and counterweight, (4) pitman, (5) walking beam, (6) horsehead, (7) bridle, (8) Samson post, (9) carrier bar, (10) polished rod clamp, (11) polished rod, (12) stuffing box, (13) pumping tee, (14) tubing ring, (15) casing head, (16) casing surface string, (17) tubing string, (18) sucker rod, (19) pump barrel, (20) pump plunger, (21) traveling valve, (22) standing valve, (23) mosquito bill, (24) gas anchor, (25) casing oil string, (26) fluid level, (27) casing perforations (National Supply)

FIGURE 1 Sucker rod pumping system: (1) prime mover, (2) gear reducer (3) crank and counterweight, (4) pitman, (5) walking beam, (6) horsehead, (7) bridle, (8) Samson post, (9) carrier bar, (10) polished rod clamp, (11) polished rod, (12) stuffing box, (13) pumping tee, (14) tubing ring, (15) casing head, (16) casing surface string, (17) tubing string, (18) sucker rod, (19) pump barrel, (20) pump plunger, (21) traveling valve, (22) standing valve, (23) mosquito bill, (24) gas anchor, (25) casing oil string, (26) fluid level, (27) casing perforations (National Supply)

FIGURE 2 Operation of a tubing pump
TABLE 1 Mechanical properties of sucker rods
Survival Treasure

Survival Treasure

This is a collection of 3 guides all about survival. Within this collection you find the following titles: Outdoor Survival Skills, Survival Basics and The Wilderness Survival Guide.

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