Design of Sucker Rod Pump
March 28
2010
Offshore oil and gas production PE6060
Abhishek Joshi PE10M001 Pramod P ME07B028
Introduction Artificial lift is the use of artificial means to increase the flow of fluids, mostly crude oil or water from a production well. This can be achieved by a number of ways, the two well-known ones being, 1. Use of mechan mechanical ical devic device e inside inside the well, well, ex. ex. Pump 2. By injecting injecting gas gas into the well well to decrease decrease the weight weight of the hydrosta hydrostatic tic column, These measures are required in wells where there is insufficient pressure in the reservoir to lift the produced fluids to the surface.
Sucker Rod Pump It is also known as Beam / Horse H orse head / Thirsty bird / Nodding donkey. It is an over ground drive for a reciprocating piston pump installed in an oil well.
A SRP converts the rotary mechanism of the motor to a vertical reciprocating motion to drive the pump shaft, and is exhibited in the characteristic characteristic nodding motion. The engineering term for this type of mechanism is a walking beam. The five major components components of a SRP SRP are 1. 2.
the prime prime mover, mover, which which provid provides es power power to the the system system the gear reducer, reducer, which which reduces the speed of the prime prime mover to a suitable pumping speed
3. the pumping unit, which which translates translates the rotating motion motion of the gear reducer and prime mover into a reciprocating reciprocating motion 4.
the sucker rod string, string, which which is located inside inside the production tubing, and and which transmits the reciprocating motion of the pumping unit to the subsurface pump
5. the the subs subsur urfa face ce pum pump p Prime Mover
The prime mover, which may be either an internal-combustion internal-combustion engine or an electric motor, provides power to the pumping unit. The choice of prime mover for a particular well depends on the field conditions and type of power available. Gear Reducer The gear reducer reducer is used to convert convert the high speed and low torque generated generated by the prime mover into the low speed and high torque required by the pumping unit. The gears are are continually lubricated lubricated by an oil oil reservoir contained contained within the assembly. When in place at the well, the gear train is mounted in an enclosed box. Pumping unit The pumping unit unit changes the the rotational motion motion of the prime mover mover to a reciprocating reciprocating vertical motion. The unit is driven by the crankshaft on the gear reducer, and is connected to a polished rod and a sucker rod string, which drives the subsurface pump. Pumping units employ a counterbalance (usually adjustable weights or pressurized air), which opposes the weight of the sucker rod string. Sucker Rod The subsurface subsurface pump is connected connected to the pumping pumping unit on the surface surface by a string string of solid sucker rods. These rods. These rods are either 25 or 30 foot in length, length, and have APIstandard diameters of 1/2, 5/8, 3/4, 7/8, 1 and 1-1/8 inch.
Subsurface pumps The subsurface subsurface pump consists consists of the working working barrel, the the plunger, the travelling travelling valve and the standing valve. It is actuated by the up and down motion of the sucker rods.
Operation of SRP
In the downstroke, as the plunger approaches approaches the bottom, the traveling valve is open, and so the standing valve is closed because it is carrying the weight of the fluid above it. At this point in the cycle, the fluid above the standing valve is moving upward through the open traveling valve. During the upstroke, the plunger has
reached the bottom of the stroke and is just beginning to move upward. The plunger starts to lift the weight of the fluid above it, and the traveling valve closes. As the plunger continues to move upward, the volume in the working barrel— between the standing valve and traveling valve—increases, while the pressure in the working barrel decreases. As soon as this pressure becomes less than the flowing bottomhole pressure, the standing valve opens and formation fluids flow upward. During each upward movement of the plunger, wellbore fluids are lifted a distance equal to one full stroke length. When the plunger reaches the top of its stroke, its movement is reversed—the traveling valve opens, the standing valve closes and the cycle repeats its reciprocating movement of the rods and the opening and closing of the two valves. With each stroke, fluid is moved up the tubing toward the surface.
Design of Sucker Rod Pump Available Data: 1. All Allowe owed d Sol Solids ids:: 500m 500mg/l g/l 2. Flui Fluid d Dens Densit ity: y: 10 10 API API 3. Vis Viscos cosity ity of of Fluid Fluid:: 1000c 1000cp p 4. Dept Depth: h: 50 500f 0ftt 5. Lift Lift rate rate:: 400 400bp bpd d 6. Bottom Bottom Hol Hole e Assem Assembly bly:: 3.5” 3.5” 7. Temp Temper erat atur ure: e: 10 100 0oC 8. All Allowe owed d Sand Sand Size: Size: 0.01”-0 0.01”-0.00 .001” 1” Parameters Needed to Design SRP 1. Stro Stroke ke Leng Length th 2. Pumpin Pumping g Stro Strokes kes per Minut Minute e 3. Polished Polished Road Road Load Load (Minimum (Minimum and Maximum) Maximum) 4. Coun Counte terr Weig Weight hts s 5. Torque
Calculation of Stroke Length From Design Data given API for Sucker Rod Pump s
Assuming volumetric efficiency efficiency as 0.8, the pump displacement is 400bpd. For depth 5000ft and pump displacement 400bpd, from the Sucker rod Pumping unit selection Chart the stroke length is 82 in. From design data table, for size 320API size and stroke 84inch (as 82 stroke is not available choose 84 strokes) Conventional Pumping Unit API Geometry Dimensions
Leng Length th of suck sucker er rod rod in feet feet=4 =499 995, 5, Tubi Tubing ng size size in inch inches es=2 =2.5 .5,, Plun Plunge gerr size size,, 3 inches=1.75, Sucker rod size, inches=1, Sp.wt of steel, lb/ft =490 API geometry dimensions for sucker rod pump (from designation C-320D-213-86) are as follows(as 84 stroke is not available choose 86 stroke)
A=111, C=96.05, I=96, I=96, P=114, H=180, G=63, G=63, R1=37, R2=32, Cs=450, T=41.61.
Stroke Length ››› Substituting the values from the above data obtained from the charts we get S = 85.518 inches
Pumping Strokes per Minute
Putting the values in the equation above, we get N= 30.07 radian/minute
Calculation of Polished Rod Loads
D = Length of the Sucker Rod, 4995 ft Tubing Size = 2.5 inches Ap = Plunger Cross Sectional Area (inch 2), Size of Plunger is 1.75 inches Ar = Sucker Rod Cross Sectional Area (inch 2), Size of Sucker Rod is 1 inch
= Density of Steel, 490 lb/ft 3 Sf = Liquid Density Substituting the values (PRL)max = 38503.396 lb (PRL)min = 10352.177 lb
Calculation of Counter Weights
This gives Counter Counter Weight as 24427 lb
Calculation of Torque
This gives the torque needed to be equal to 733802.267 lb-inches
Advantages of Sucker Rod Pumps 1) They can can reduce reduce bottom hole hole pressure pressures s to very low levels levels 2) Offer great great flexibili flexibility ty for low to medium medium product productions ions 3) Simple Simple with respect respect to design, design, operation operation and mainten maintenance ance 4) Surface and and downhole downhole equipment equipment can easily be refurbished, refurbished, and tends to have high salvage values 5) Most widely widely known known and well-und well-underst erstood ood systems systems in the field field 6) High lift lift capaci capacity ty compared compared to to PCP and and ESP 7) Suitable for all kinds of wells as against against PCP which is suitable suitable only for oil wells
8) High efficienc efficiency y of about about 80-90% 80-90% 9) They are suitable for high temperature reservoirs, where ESP experiences seal damage 10) Have a displacement capacity up to 500 bpd, compared to high capacities of ESP and PCP.
11) Lower power consumption for unit production. production. 12)
Optimization controls are available
In case of sand producing wells, with slight modification to the bottom hole 13) assembly SRPs can be effectively used
Latest advancements in SRP Recent and advanced applications of the beam pumping system are successful for overcoming severe industry problems like, 1) Produc Producing ing high high volu volume me wells wells 2) Produc Productio tion n of high/oi high/oill wells wells 3) Handling Handling high high sand content content fluid fluids s 4) Accurate Accurate monitor monitoring ing and and control control of of the well well 5) Producin Producing g from highly highly deviated deviated and and horizonta horizontall wells Optimization controllers for rod pumping With the advent of automation in the oilfield, rod pump control has become an industry standard. While the rod pump controller (RPC) has advanced in reliability and accuracy, the basic principles remain unchanged. Those principles include load and position control, minimizing pump-off and providing data for analysis of the well. Many advances have improved the communication of data, the accuracy of the data collected, and the logic used to provide control. The controller gathers data from the well through load and position sensors and uses the data to calculate downhole pump fillage and optimize production on each stroke. This information is used to minimize fluid pound by stopping or slowing down the pump at the assigned downhole pump fillage setting. By using the unabbreviated application of the wave equation, the well can be controlled with unprecedented accuracy, which enables real-time and historical production production measurement to be stored in the controller for up to 120 days. With the recent technology and properly designed SRP systems are highly successful successful in very high Gas/liquid ratio wells, de‐ liquefying gas wells and the leading system in coal‐bed methane
Pampa style SRP – They have a longer than normal plunger and a shorter than normal barrel. In the upstroke the plunger pulls sand away from the plunger/ barrel interface minimizing the effects of pressure.
Farr plunger – This increases the pump life and cut well pulling cost drastically.The connector has been moved from the top of the plunger to the bottom of the plunger. This eliminates the gap, wedge and funnel which creates the problems for the conventional plunger. Also, the angle at the top of the plunger has been reversed to force sand inward.
These days even horizontal horizontal wells wells are drilled with SRP. Only wells wells drilled with short radius tools or wells that have extreme deviation changes due to steering drift are problematic. Programs like S‐ROD with the deviation survey plugged in can predict and design SRP systems for deviated wells. Coiled rods contain only two connections connections – one at the top and one at the bottom. They reduce the the wear on rod and and tubing. They give give increased production production because because of no coupling piston effect, which reduces the friction and increases the plunger over travel. This also decreases the maintenance costs.
Indian companies involved in SRP manufacturing/ manufacturing/ distribution - Aaka Aakash sh oil oil fie field ld s ser ervi vice ces s pvt pvt lim limit ited ed - Sela Selan n expl explor orat atio ion n tech techno nolo logy gy lim limit ited ed
References
• • • • •
• • •
Wikipedia www.norrisrods.com Rod Pumping overview (Google search result) Well-pilot optimization controller for rod pumping Advancements in the area of SRP applications (M Ghareeb, Director: ALS Lufkin) www.aoscoly.com www.muthpump.com The technology of of artificial lift lift – Kermit E Brown Brown