COROD Continuous Rod

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Weatherford COROD® continuous rod is designed for medium- to heavy-load reciprocating rod lift (RRL) and progressing cavity pumping (PCP) wells that are noncorrosive or mildly corrosive but effectively inhibited.

This product is available in various grades and in multiple sizes of round- and semi-elliptical- shaped rod designed to suit a wide range of applications.

With only two required couplings, one at the top and one at the bottom of the rod string, COROD continuous rod provides an excellent alternative to conventional sucker rods. By reducing the number of threaded connections, the COROD solution decreases pin and coupling failures, which minimizes the potential for rod string failures and costly well interventions.

The uniform body design is specifically engineered to evenly disperse contact loads throughout the entire rod string, eliminating wear at localized points and extending the lifespan of the tubing. COROD continuous rod is lighter in weight than conventional sucker rods and therefore reduces the power requirements of surface motors. Installation is quick, and Weatherford offers a full array of field servicing options.

Applications

  • Progressing cavity pumping systems – round product only
  • Reciprocating-rod-lift systems – round and semi-elliptical product
  • Light crude, cold heavy-oil production with sand (CHOPS), cyclic steam, steam flood, and steam-assisted gravity drainage (SAGD) wells

Features and Benefits

  • Fewer threaded connections on the rod string reduce the potential for pin and coupling failures as well as the need for costly well interventions.
  • The uniform body design evenly distributes contact loads over the entire rod string, reducing the severity of tubing and rod wear.
  • The large, uninterrupted annular tubing space minimizes pressure losses and ensures laminar, nonturbulent flow to the wellhead.
  • COROD strings are lighter than conventional sucker-rod strings─which reduces the total weight on the service unit─and they are capable of reaching lower pump-landing depths.
  • The finished COROD product undergoes a cold-working process (known as shot peening) to produce a residual stress on the outside layer of the material that increases resistance to fatigue and corrosion failure.

Product Types

Every grade of Weatherford COROD continuous rod is manufactured using a quench and temper heat treatment.

D Grade Regular-Strength

D Grade Regular-Strength product is designed for medium-load pumping applications in noncorrosive or mildly corrosive but effectively inhibited wells where H2S may be present.

  • 1536M Material
  • Available in round sizes 3R to 8.5R
  • Available in semi-elliptical sizes 2E to 8E
  • API Grade D Carbon

DE Grade Regular-Strength

DE Grade Regular-Strength product is designed for medium-load pumping applications in noncorrosive or mildly corrosive but effectively inhibited wells where CO2 or chlorides may be present. DE is made from a chrome-molybdenum alloy, micro-alloyed with titanium to improve mechanical and heat-treating properties. DE chromium content is increased to 2 percent to improve corrosion resistance in certain applications.

  • 4120M Material
  • Available in round sizes 4R to 8.5R
  • Available in semi-elliptical sizes 3E to 8E
  • API Grade D Alloy

DW Grade Regular-Strength

DW Grade Regular-Strength product is designed for medium-load pumping applications in mildly corrosive or more corrosive but effectively inhibited wells. DW is made from a chrome-nickel-molybdenum alloy, specifically formulated to improve stress tolerance and fatigue resistance.

  • 4320M Material
  • Available in round sizes 6R and 8.5R
  • API Grade D Alloy

ME Grade Mid-Strength

ME Grade Mid-Strength product is designed for medium-load pumping applications in deep, high-volume wells for noncorrosive or mildly corrosive environments that are effectively inhibited. ME is made from a chrome-molybdenum alloy, micro-alloyed with titanium to improve mechanical and heat-treating properties. ME chromium content is increased to 2 percent to improve corrosion resistance in certain applications.

  • 4120M Material
  • Available in round sizes 6R and 8.5R
  • Available in semi-elliptical sizes 3E to 8E
  • API Grade D Alloy

SE Grade High-Strength

SE Grade High-Strength product is designed for heavy-load pumping applications in deep, high-volume wells for mildly corrosive or corrosive environments that are effectively inhibited. SE is made from a chrome-molybdenum alloy, micro-alloyed with titanium to improve mechanical and heat-treating properties. SE chromium content is increased to 2 percent to improve corrosion resistance in certain applications.

  • 4120M Material
  • Available in round sizes 3R to 8.5R
  • Available in semi-elliptical sizes 3E to 8E
  • API Grade D Special

SW Grade High-Strength

SW Grade High-Strength product is designed for heavy-load pumping applications in mildly corrosive or more corrosive but effectively inhibited wells. DW is made from a chrome-nickel-molybdenum alloy, specifically formulated to improve stress tolerance and fatigue resistance.

  • 4320M Material
  • Available in round sizes 3R to 8.5R
  • API Grade D Special

The Semi-Elliptical COROD Continuous Rod Advantage

Weatherford semi-elliptical COROD continuous rod is a uniquely shaped rod product designed to optimize reciprocating-rod-lift (RRL) applications. It fits the curvature of the tubing string and results in less tubing contact pressure than with continuous round rods and conventional sucker rods. Semi-elliptical COROD continuous rod is manufactured in seven diameters (at 1/16-in. increments), allowing you to custom design your taper rod string to any length.

Features and Benefits of Semi-Elliptical COROD Continuous Rod

  • The elliptical body design further reduces contact loading between the rod and tubing, resulting in less localized wear and fewer part replacements.
  • The ribbon-like shape of the rod promotes predictable bending along one plane, eliminating rod damage caused by a coiling or springing effect.
  • The formed, semi-elliptical design minimizes surface discontinuities, increasing the life of your rod string in RRL applications.
  • The rod maintains a minor diameter of less than 3/4 in., which prevents the rod from undergoing stresses exceeding its yield strength when coiled onto transport reels.

Specifications

 

API Grade
Codes
Material
Tensile Strength (min.)
Yield Strength (min., 0.2% offset)
Elong (min.)
Hardness (max.)
psi
MPa
psi
MPa
%
Rockwell
Brinell
D Carbon
D, DR
1536M
115,000
790
85,000
590
10
28
271
D Alloy
DE, DER
4120M
115,000
790
90,000
620
10
28
271
D Alloy
DWR
4320M
115,000
790
90,000
620
10
30
286
D Alloy
ME, MER
4120M
130,000
896
110,000
758
7
32
301
D Special
SE, SER
4120M
140,000
965
115,000
790
4.5
36
336
D Special
SWR
4320M
145,000
1,000
120,000
825
4.5
38
353

 

COROD #
Size
Codes
in.
mm
DR/DER
MER
SER
DWR
SWR
8.5
1-5/32
29.4
1,490 ft-lbf
2,020 N∙m
1,845 ft-lbf
2,501 N∙m
2,000 ft-lbf
2,712 N∙m
1,490 ft-lbf
2,020 N∙m
2,000 ft-lbf
2,712 N∙m
6
1
25.4
955 ft-lbf
1,295 N∙m
1,195 ft-lbf
1,620 N∙m
1,300 ft-lbf
1,763 N∙m
955 ft-lbf
1,295 N∙m
1,300 ft-lbf
1,763 N∙m
4
7/8
22.2
640 ft-lbf
868 N∙m
N/A
900 ft-lbf
1,220 N∙m
N/A
900 ft-lbf
1,220 N∙m
3
13/16
20.6
500 ft-lbf
678 N∙m
N/A
700 ft-lbf
949 N∙m
N/A
700 ft-lbf
949 N∙m

 

COROD #
Nominal Size
Weight
Area (min.)
Major Diameter
Minor Diameter
in.
mm
lb/ft
kg/m
in.2
mm2
in. (±0.020)
mm (±0.5)
in. (±0.020)
mm (±0.5)
8
1-1/8
28.6
3.38
5.03
0.994
641.3
1.570
39.9
0.745
18.9
7
1-1/16
27.0
3.01
4.49
0.887
572.0
1.430
36.3
0.745
18.9
6
1
25.4
2.67
3.98
0.785
506.7
1.260
32.0
0.740
18.8
5
15/16
23.8
2.35
3.50
0.690
445.3
1.115
28.3
0.730
18.5
4
7/8
22.2
2.04
3.05
0.601
387.9
1.005
25.5
0.700
17.8
3
13/16
20.6
1.76
2.63
0.518
334.5
0.940
23.9
0.650
16.5
2
3/4
19.1
1.50
2.24
0.442
285.0
0.870
22.1
0.600
15.2
8.5R
1-5/32
29.4
3.57
5.32
1.050
677.4
1.156
29.4
NA
NA
6R
1
25.4
2.67
3.98
0.785
506.7
1.000
25.4
NA
NA
4R
7/8
22.2
2.04
3.05
0.601
387.9
0.875
22.2
NA
NA
3R
13/16
20.6
1.76
2.63
0.518
334.5
0.812
20.6
NA
NA

 

Material
C
Mn
P
S
Si
Ni
Cr
Mo
Al
Ti
Cu
1536M
0.31 to 0.35
1.10 to 1.30
0.015
0.010
0.15 to 0.35
0.25 (max.)
0.25 (max.)
0.050 (max.)
0.020 to 0.050
0.35 (max.)
4320M
0.17 to 0.22
0.45 to 0.65
0.015
0.010
0.15 to 0.35
0.95 to 1.10
0.95 to 1.10
0.20 to 0.30
0.020 to 0.050
0.005 to 0.020
0.20 to 0.30
4120M
0.18 to 0.23
0.40 to 0.60
0.015
0.010
0.15 to 0.30
0.25 (max.)
1.80 to 2.00
0.15 to 0.20
0.020 to 0.050
0.005 to 0.020
0.20 to 0.30