Sucker Rod Pump

Transcription

1 Sucker Rod Pump

2 Sucker Rod Pump

3 Sucker Rod Pump

4 Sucker Rod Pump 4

5 Sucker Rod Pump 5

6 Sucker Rod Pump High System Efficiency Optimization Controls Available Sucker Rod Sucker Rod Pump Assembly Tubing Anchor/ Catcher Economical to Repair and Service Positive Displacement/Strong Drawdown Upgraded Materials Reduce Corrosion Concerns Flexibility - Adjust Production Through Stroke Length and Speed High Salvage Value for Surface & Downhole Equipment 6

7 Rod Pump Potential for Tubing and Rod Wear Sucker Rod Sucker Rod Pump Assembly Tubing Anchor/ Catcher Gas-Oil Ratios Most Systems Limited to Ability of Rods to Handle Loads Volume Decreases As Depth Increases Environmental and Aesthetic Concerns 7

8 Rod Pump Sucker Rod Sucker Rod Pump Assembly Tubing Anchor/ Catcher Typical Range Maximum* Operating Depth ,000 TVD 16,000 TVD Operating Volume BPD 5000 BPD Operating Temperature F 550 F Wellbore 0-20 Landed 0-90 Landed Deviation Pump Pump - <15 /100 Build Angle Corrosion Handling Gas Handling Solids Handling Fluid Gravity Servicing Prime Mover Type Offshore Application Good to Excellent w/ Upgraded Materials Fair to Good Fair to Good >8 API Workover or Pulling Rig Gas or Electric Limited System Efficiency 45%-60% 8

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10 Sucker Rod Pump

11 Sucker Rod Pump

12 Sucker Rod Pump 12

13 Sucker Rods

14 Sucker Rod Pump The pumpjack is the visible above-ground drive for the well pump, and is connected to the downhole pump at the bottom of the well by a series of interconnected sucker rods. Sucker rods are usually installed in a taper. Rods come in steel and fiberglass Steel rods typically come in ¾, 7/8, and 1 and are usually 25 long Fiberglass rods are typically 1 and 1-1/4 and are usually 37.5 long Rods are connected by a coupling, the coupling is either a T or Spray metal

15 Fiberglass Rods The Fiberglass rod gives the rod string more elasticity, providing over travel of the pump, therefore providing more production. The 2 FG rods weigh less than 3 steel rods, this allows the operator to use a smaller pump jack The FG rod is corrosion resistant due to its make up

16 Steel Rods Steel Rods are the most basic form of ALS Available in a variety of sizes and come in 25 lengths Available in a variety of grades Grade AD is a basic sucker rod with Standard tensile strength and is good for little to no corrosion environments Grade KD is a more corrosion resistant rod with the standard characteristics just like the AD such as tensile strength Grade HS is a high strength rod with a higher tensile rating than the AD & KD rod, not good for corrosive environments

17 Polish rod Pony rods Fiberglass Steel Sinker bars Pump The sequence of rods being run in the well.

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21 Stationary Barrel Bottom Anchor Rod Pump-RHBC and RHBM Stationary Barrel Top Anchor Rod Pump-RHAM and RHAC Traveling Barrel Bottom Anchor Rod Pump-RHTC and RHTM

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26 Most Important Operating Parameters of Sucker- Rod Pumping: Polish rod loads Downhole stoke length of plunger Torque reducer

27 Polish Rod Loads:

28 Dynamic Loads Given By:

29 Polish Rod Loads:

30 Polish Rod Loads:

31 Polish Rod Loads:

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34 Effective Plunger Stroke: The motion of the plunger at the pumpsetting depth and motion of the polished rod do not coincide in time and magnitude. It is due to elasticity of sucker rods and tubing strings. Plunger motion is affected by: Polished rod motion Sucker rod stretch Tubing stretch

35 Two major sources of difference in the motion of polished rod and plunger: 1. Elastic stretch (Rod String) Periodic transfer of the fluid from SV to TV and back again The result is a function of stretch in rod string and tubing Rod string is stretched by weight of the fluid column in the tubing coming on to the rod string at the bottom of the stroke when TV closes This load is is removed from the rod string at the top of the stroke when TV opens. Plunger stroke will be less by an amount equal to rod stretch

36 Two major sources of difference in the motion of polished rod and plunger: 2. Plunger Overtravel Plunger overtravel at the bottom of stroke is a result of upward acceleration imposed on the downward moving sucker rod elastic system Plunger stroke will be more by an amount equal to plunger overtravel Also tubing stretch will reduce the plunger stroke and sometimes neglected as area of cross section of tubing is higher as compare to c/s area of rod.

37 Effective Plunger Stroke: 1. The magnitude of the rod stretch is given by:

38 Effective Plunger Stroke: 2. Plunger Overtravel: Where n is acceleration factor:

39 Effective Plunger Stroke: 2. Plunger Overtravel:

40 Effective Plunger Stroke (Sp):

41 Pump displacement and production rate: There are two aspects to consider when sizing the downhole pump for an installation. The first is that the pump capacity should be related to the well capacity. The pump displacement is determined on the basis of the pumping speed, unit stroke length, and plunger diameter. The general equation is:

42 Pump displacement and production rate: The theoretical pump displacement given by the area of pump barrel multiplied by the effective plunger stroke length. V = Ap (inch 2 in ) S p ( stroke ) N(stroke min = A p S p N (bbl/day) Volumetric efficiency given by: E v = q V q- actual production rate ) 1440 min/day 9702 inch3/bbl

43 Pump displacement and production rate: The second aspect of pump sizing, once the pump diameter is selected, is ensuring that the downhole pump is properly built. The main component that needs to be sized is the barrel length, which should be long enough to accommodate the plunger length, the downhole stroke length, all fittings etc. The minimum plunger length recommended is normally 3 ft. It is recommended that the length of the plunger is increased 1 ft/1,000 ft of well depth, up to a 6-ft maximum length.

44 Counterbalance Design: 1. Crank Counter Balance System; in this type the counter weight mounted on the crank. 2. Beam Counter Balance System; in this type balancing load (counter weight) mounted on walking beam.

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47 Counterbalance Design: Counterbalance act as a way of storing energy and releasing energy Storing Energy During Down-Stroke Releasing Energy During Up-Stroke The theoretical (ideal) counterbalance effect Ci considered as average of Up-stroke and Down-stroke C i = W max + W min 2

48 Counterbalance Design: (FBD)

49 Counterbalance Design: (FBD) Cw- Counterbalance Effect Wc- Counter Weight β- Angle between walking beam and Horizontal θ- Angle between Crank and Vertical γ- Angle between Pitman and Vertical d- Distance from crankshaft to center of gravity of counterweight r- Distance from crankshaft to pitman bearing Fp- Force in the pitman L1- Distance from saddle bearing to tail bearing L2- Distance from saddle bearing to briddle

50 Counterbalance Design: (FBD) Considering the horizontal and vertical components of force Fp an taking moments about saddle bearing:

51 Counterbalance Design: Considering the horizontal and vertical components of force Fp an taking moments about saddle bearing: Solving for Fp: Equation 1 Summing moments about the crankshaft:

52 Counterbalance Design: Summing moments about the crankshaft: Solving for Fp: Equation 2 Solving equation 1 and 2 and assuming γ very small:

53 Pump with a polished rod strike length of 64 inch is inserted in a well having fluid of specific gravity The rod and fluid loads were calculated as 7433 lbf an 3311 lbf respectively. The unit has structural unbalance of +670 lbf, the saddle bearing is half way between the bridle and tai bearing and counterbalance weighs 5250 lbf. How far the crankshaft should the center of gravity of the counterweight be placed on the crankshaft to obtained theoretical counter effect? Assume N = 20 SPM C i = W max + W min 2 C i = W max+w min 2 = 8675 lbf = ( )/2 L1=L2 and r= 32 will give d= 48.8 inch

54 Calculation of Torque: Consider the figure given below: W O θ r Wc d Consider the equation for counter weight: If L1= L2 the equation becomes C i = 2Wc d S

55 Calculation of Torque: Consider the figure given below: W O θ r Wc d In the figure shown the angle θ becomes 0 at the beginning of upstroke, so net torque at origin O

56 Calculation of Torque: W θ Wc C i = 2Wc d S Combining expression for counter balance: O r d

57 Calculation of Torque: The peak torque will occur when Sinθ = 1, i.e. the crank and walking beam are both in horizontal position: This expression is assuming the counterbalance of 0.95 of the ideal value.

58 Calculation of Torque: Calculate the expected peak torque if the maximum polished rod load is lbf and ideal counter effect of 8675 lbf. T p = = lb. inch

59 Speed Reduction from motor to Crankshaft: Power is typically transmitted to gear box from motor through V- belts and Sheaves All points on the belt are moving at same velocity so the outer edge of sheave at same velocity The velocity is given by πdω We can write πdu Nu = πdene N u = N e d e d u If the gear ratio at the reducer is Z Pumping speed (N) = N u Z = N ed e Zd u

60 Calculation of sheave diameter: A 1200 rpm electric motor is being used as the prime mover for a unit operating at 20 SPM. The double reduction gear reducer has a gear ratio of to 1, and the unit sheave has pitch diameter of inch. Calculate the diameter of the sheave to be used on the motor. Pumping speed (N) = d e = Zd u N u Z = N ed e Zd u N Ne = = 9. 4 inch

61 Power Requirement: Need to overcome: The potential energy Frictional energy loss H h = q(bbl d ) 350G(lbf bbl ) L N(ft) (1440 min ft. lbf )(33000 d hpmin ) H h = qgl N hp L N = L = (D P csg 0.433G csg + L D P tbg 0.433G tbg ) P csg C csg + P tbg 0.433G tbg H f = W r SN

62 Calculation of horsepower requirement: A well has a production rate of 350 bbl/d (G=0.87) with a polished rod stroke length of 64 inch and a pumping speed of 20SPM. Depth to the pump is 4560 ft and the weight of the sucker rod string is 7433 lbf. Assuming the pump is set at the working fluid level and neglecting tubing pressure calculate the horsepower rating of the motor. H h = qgl N hp H h = H h = 10. 4hp H f = W r SN H f = = 6.15 hp Total = = 24 hp

63 Calculation of horsepower requirement: If the tubing pressure is 50 psig and casing pressure is 0 and the pump is submerged 250 ft below working fluid level what is net lift? L N = (D P csg 0.433G csg + P tbg 0.433G tbg L N = ( ) = 4443 ft