OCTG (Tubing and Casing)

OCTG (Tubing and Casing)

OCTG (Oil Country Tubular Goods) refers to a group of rolled metal products used in the oil and gas industry, including casing and tubing. They are indeed used in the drilling process.

Casing is a term that refers to the tubing that is installed inside a drilled well to protect and support the well stream. The Casing completely surrounds the wellbore, protecting the soil layers and, most importantly, the groundwater from contamination by drilling mud and frac fluids. Additionally, it stabilizes the wellbore, which means that the casing must be able to withstand extremely high loads.

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With over 500,000 tons annual production capacity, the company serves various fields and industries, such as oil & gas exploitation and transmission, ship & auto-building, water & electricity, environmental protection, mechanical engineering, infrastructure construction and etc.

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Production Standard of OCTG (Tubing and Casing)

  • API 5CT specified that casing and tubing used in OCTG production must be cased with a material that is both strong and functional. The standard establishes requirements for three Product Specification Levels (PSL-1, PSL-2, and PSL-3) and a variety of grades (API 5CT J55, K55, N80, L80, P110).

Types of OCTG (Tubing and Casing)

Lining with Casing

Casing refers to the external tubes. Casing completely surrounds the wellbore, protecting the soil layers and, most importantly, the groundwater from contamination by drilling mud and/or frac fluids. Additionally, it stabilizes the wellbore, which means that the casing must be able to withstand extremely high loads. Drilling and casing operations alternate – the drill string is removed at predetermined intervals and the wellbore is lined and cemented with casing. Then the drilling resumes.

Production with Tubing

Tubing is used to carry petroleum from the well’s depths to the surface – this is the third phase of the wellbore. Oil and gas occasionally self-elevate to the surface; however, pumps are typically required to bring the fluids to the surface.

Besides the 4 1/2-inch diameter, tubing is normally smaller in diameter than casing. A casing or tubing with an outer diameter of 114.3 mm (4 1/2 inches) is considered a threshold size. Anything smaller than tubing is referred to as tubing, while anything larger is referred to as casing.

The casing shrinks in diameter as it descends from the surface to the bottom of the well – there are various types of casing depending on their purpose and diameter. The “kickoff point” is the gradual transition of the wellbore from vertical to horizontal. Horizontal drilling enables more precise targeting of deposits. At the conclusion of the procedure, the drill string is removed and the production casing is inserted and cemented into the wellbore. After fractureing the well, the tubing is installed inside the production casing.

Dimensions and Sizes of OCTG (Tubing and Casing)

- Specification & Size of Tubing

DN O. D. Weight W. T. End Processing
Non-upset coupling-thread Upset coupling-thread Steel Grade
in mm lb./ft. lb./ft. in mm H40 J55 L80 N80 C90 T95 P110
2-3/8 2.375 60.32 4.00 0.167 4.24 PU PN PN PN PN PN
4.60 4.70 0.190 4.83 PNU PNU PNU PNU PNU PNU PNU
5.80 5.95 0.254 6.45 PNU PNU PNU PNU PNU
6.60 0.295 7.49 P P P
7.35 7.45 0.336 8.53 PU PU PU
2-7/8 2.875 73.02 6.40 6.50 0.217 5.51 PNU PNU
7.80 7.90 0.276 7.01
8.60 8.70 0.308 7.82 PLB PLB PLBE PLB
9.35 9.45 0.340 8.64 PLB PLB PLBE PLB
10.50 0.392 9.96 PLB PLB PLB PLB
11.50 0.440 11.18 PLB
3-1/2 3.500 88.90 7.70 0.216 5.49 PN PN PN PN PN PN
9.20 9.30 0.254 6.45 PNU PNU PNU PNU PNU PNU PNU
10.20 0.289 7.34 PN PN PN PN PN PN
12.70 12.95 0.375 9.52 PNU PNU PNU PNU PNU
14.30 0.430 10.92 P P P
15.50 0.476 12.09 P P P
17.00 0.530 13.46 P P P
4 4.000 101.60 9.50 0.226 5.74 PN PN PN PN PN PN
11.00 0.262 6.65 PU PU PU PU PU PU
13.20 0.330 8.38 P P P
16.10 0.415 10.54 P P P
18.90 0.500 12.70 P P P
22.20 0.610 15.49 P P P
4-1/2 4.500 114.30 12.60 12.75 0.271 6.88 PNU PNU PNU PNU PNU PNU
15.20 0.337 8.56 P P P
17.00 0.380 9.65 P P P
18.90 0.430 10.92 P P P PLB
21.50 0.500 12.70 P P P PLB
23.70 0.560 14.22 P P P PLB
26.10 0.630 16.00 P P P PLB
P——Plain;N—— Non-upset coupling-thread;U—— Upset coupling-thread; L——Integral

- Specification & Size of Casing

DN O. D. Weight W. T. End Machining Form
Steel Grade
in mm lb/ft kg/m in mm H40 J55 L80 N80 C90 P110
K55 T95
4-1/2 4.500 114.3 9.50 14.14 0.205 5.21 PS PS
10.50 15.63 0.224 5.69 PSB
11.60 17.26 0.250 6.35 PSLB PLB PLB PLB PLB
13.50 20.09 0.290 7.37 PLB PLB PLB PLB
15.10 22.47 0.337 9.56 PLB
5 5.000 127 11.50 17.11 0.220 5.59 PS
13.00 19.35 0.253 6.43 PSLB
15.00 22.32 0.296 7.52 PSLB PLB PLB PLBE PLB
18.00 26.79 0.362 9.19 PLB PLB PLBE PLB
21.40 31.85 0.437 11.10 PLB PLB PLB PLB
23.20 34.53 0.478 12.14 PLB
24.10 35.86 0.500 12.70 PLB
5-1/2 5.500 139.7 14.00 20.83 0.244 6.20 PS PS
15.50 23.07 0.275 6.98 PSLB
17.00 25.30 0.304 7.72 PSLB PLB PLB PLBE PLB
20.00 29.76 0.361 9.17 PLB PLB PLBE PLB
23.00 34.23 0.415 10.54 PLB PLB PLBE PLB
26.80 39.88 0.500 12.70
29.70 44.20 0.562 14.27
32.60 48.51 0.625 15.88
35.30 52.53 0.687 17.45
38.00 56.55 0.750 19.05
40.50 60.27 0.812 20.62
43.10 64.14 0.875 22.22
6-5/8 6.625 168.28 20.00 29.76 0.288 7.32 PS PSLB
24.00 35.72 0.352 8.94 PSLB PLB PLB PLBE PLB
28.00 41.67 0.417 10.59 PLB PLB PLBE PLB
32.00 47.62 0.475 12.06 PLB PLB PLBE PLB
7 7.000 177.8 17.00 25.30 0.231 5.87 PS
20.00 29.76 0.272 6.91 PS PS
23.00 34.23 0.317 8.05 PSLB PLB PLB PLBE
26.00 38.69 0.362 9.19 PSLB PLB PLB PLBE PLB
29.00 43.16 0.408 10.36 PLB PLB PLBE PLB
32.00 47.62 0.453 11.51 PLB PLB PLBE PLB
35.00 52.09 0.498 12.65 PLB PLB PLBE PLB
38.00 56.55 0.540 13.72 PLB PLB PLBE PLB
42.70 63.54 0.625 15.88
46.40 69.05 0.687 17.45
50.10 74.56 0.750 19.05
53.60 79.77 0.812 20.62
57.10 84.97 0.875 22.22
7-5/8 7.625 193.68 24.00 35.72 0.300 7.62 PS
26.40 39.29 0.328 8.33 PSLB PLB PLB PLBE PLB
29.70 44.20 0.375 9.52 PLB PLB PLBE PLB
33.70 50.15 0.430 10.92 PLB PLB PLBE PLB
39.00 58.05 0.500 12.70 PLB PLB PLBE PLB
42.80 63.69 0.562 14.27 PLB PLB PLB PLB
45.30 67.41 0.595 15.11 PLB PLB PLB PLB
47.10 70.09 0.625 15.88 PLB PLB PLB PLB
51.20 76.19 0.687 17.45
55.30 80.30 0.750 19.05
8-5/8 8.625 219.08 24.00 35.72 0.264 6.71 PS
28.00 41.62 0.304 7.72 PS
32.00 47.62 0.352 8.94 PS PSLB
36.00 53.57 0.400 10.16 PSLB PLB PLB PLBE PLB
40.00 59.53 0.450 11.43 PLB PLB PLBE PLB
44.00 65.48 0.500 12.70 PLB PLB PLBE PLB
49.00 72.92 0.557 14.15 PLB PLB PLBE PLB
9-5/8 9.625 244.48 32.30 48.07 0.312 7.92 PS
36.00 53.57 0.352 8.94 PS PSLB
40.00 59.53 0.395 10.03 PSLB PLB PLB PLBE
43.50 64.73 0.435 11.05 PLB PLB PLBE PLB
47.00 69.94 0.472 11.99 PLB PLB PLBE PLB
53.50 79.62 0.545 13.84 PLB PLB PLBE PLB
58.40 86.91 0.595 15.11 PLB PLB PLB PLB
59.40 88.40 0.609 15.47
64.90 96.58 0.672 17.07
70.30 104.62 0.734 18.64
75.60 112.50 0.797 20.24
10-3/4 10.750 273.05 32.75 48.74 0.279 7.09 PS
40.50 60.27 0.350 8.89 PS PSB
15.50 67.71 0.400 10.16 PSB
51.00 75.90 0.450 11.43 PSB PSB PSB PSBE PSB
55.50 82.59 0.495 12.57 PSB PSB PSBE PSB
60.70 90.33 0.545 13.84 PSBE PSB
65.70 97.77 0.595 15.11 PSB PSB
73.20 108.93 0.672 17.07
79.20 117.86 0.734 18.64
85.30 126.94 0.797 20.24
11-3/4 11.750 42.00 62.50 0.333 8.46 PS
47.00 69.94 0.375 20.24
54.00 80.36 0.435 8.46
60.00 89.29 0.489 9.53
65.00 96.73 0.534 11.05
71.00 105.66 0.582 14.42
13-3/8 13.375 339.73 48.00 71.43 0.330 8.38 PS
54.50 81.10 0.380 9.65 PSB
61.00 90.78 0.430 10.92 PSB
68.00 101.19 0.480 12.19 PSB PSB PSB PSB PSB
72.00 107.15 0.514 13.06 PSB PSB PSB PSB
16 16.000 406.4 65.00 96.73 0.375 9.53 PS
75.00 111.61 0.438 11.13 PSB
84.00 125.01 0.495 12.57 PSB
109.00 162.21 0.656 16.66 P P P P
18-5/8 18.625 473.08 87.50 130.21 0.435 11.05 PS PSB
20 20.000 508 94.00 139.89 0.438 11.13 PSL PSLB
106.50 158.49 0.500 12.70 PSLB
133.00 197.93 0.635 16.13 PSLB
P——Plain;S——Short-thread;L——Long-thread;B——Buttress thread;E——Extreme thread

- Chemical Composition of OCTG (Tubing and Casing)

Group Steel Grade Type C Mn Mo Cr Ni Cu P S Si
min. max. min. max. min. max. min. max. min. max. max. max. max.
1 H40 0.03 0.03
J55 0.03 0.03
K55 0.03 0.03
N80 1 0.03 0.03
Q 0.03 0.03
2 M65 0.03 0.03
L80 1 0.43 1.9 0.25 0.35 0.03 0.03 0.5
9Cr 0.15 0.3 0.6 0.9 1.1 8 10 0.5 0.25 0.02 0.01 1.0
13Cr 0.15 0.22 0.25 1 12 14 0.5 0.25 0.02 0.01 1.0
C90 1 0.35 1.2 0.25 0.85 1.5 0.99 0.02 0.01
2 0.5 1.9 NL NL 0.99 0.03 0.01
C95 0.45 1.9 0.03 0.03 0.5
T95 1 0.35 1.2 0.25 0.85 0.4 1.5 0.99 0.02 0.01
2 0.5 1.9 0.99 0.03 0.01
3 P110 0.03 0.03
4 Q125 1 0.35 1.35 0.85 1.5 0.99 0.02 0.01
2 0.35 1 NL NL 0.99 0.02 0.02
3 0.5 1.9 NL NL 0.99 0.03 0.01
4 0.5 1.9 NL NL 0.99 0.03 0.02
a. The carbon content for L80 may be increased up to 0, 50 % maximum if the product is oil-quenched. b. The molybdenum content for Grade C90 Type 1 has no minimum tolerance if the WT is less than 17, 78 mm. c. The carbon content for R95 may be increased up to 0, 55 % maximum if the product is oil-quenched. d. The molybdenum content for T95 Type 1 may be decreased to 0, 15 % minimum if the WT is less than 17, 78 mm. e. For EW Grade P110, the phosphorus content shall be 0,020 % maximum and the sulfur content 0,010 % maximum NL = no limit. Elements shown shall be reported in product analysis.

- Mechanical Properties Tensile Strength and Yield Strength of OCTG (Tubing and Casing)

Group Steel Grade Type Total % Yield Strength MPa Tensile MPa Hardness max W. T. mm Changes in Hardness
min. max. min. HRC HBW
1 H40 0.5 276 552 414
J55 379 552 517
K55 379 552 655
N80 1 552 758 689
Q 552 758 689
2 M65 0.5 448 586 586 22 235
L80 1 552 655 655 23 241
9Cr 552 655 655 23 241
13Cr 552 655 655 23 241
C90 1、2 621 724 689 25.4 255 ≤ 12.70 3.0
621 724 689 25.4 255 12.71 ~ 19.04 4.0
621 724 689 25.4 255 19.05 ~ 25.39 5.0
621 724 689 25.4 255 ≥25.40 6.0
C95 655 758 724
T95 1、2 655 758 724 25.4 255 ≤ 12.70 3.0
655 758 724 25.4 255 12.71 ~ 19.04 4.0
655 758 724 25.4 255 19.05 ~ 25.39 5.0
655 758 724 25.4 255 ≥25.40 6.0
3 P110 0.6 758 965 862
4 Q125 all 0.65 862 1034 931 ≤ 12.70 3.0
862 1034 931 12.71 ~ 19.04 4.0
862 1034 931 ≥19.05 5.0
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