J55 vs K55

Choosing the right casing and tubing material is crucial for safe and efficient oil and gas drilling. Under the API 5CT standard, J55 and K55 are commonly used for medium-depth wells. Though similar, they differ in key mechanical and performance properties.

1. Heat treatment 

PSL1: J55 and K55 are the same (rollable delivery);
PSL2: J55, K55 products should be the whole normalizing or normalizing and tempering, if thickened, should be thickened after normalizing or normalizing and tempering. 

2. Straightening (no difference)

3. Chemical composition (control no difference)

4. Tensile test 
J55: Yield strength is 379MPA~552MPA; tensile strength is 517MPA;
K55: Yield strength is 379MPA~552MPA; tensile strength is 655MPA;
Due to the difference in tensile strength, the required minimum elongation J55 is 19% and K55 is 15%.

5. Impact test 
Body pipe:
PSL1: No difference between J55 and K55;
PSL2: J55 and K55 require a horizontal minimum impact energy of 20 J for a full-size specimen and 27 J for a full-size specimen.
Couplings: The J55 and K55 impact tests must be performed with a minimum transverse impact energy of 20 J for size specimens and 27 J for full-size specimens in the longitudinal direction.

6. Hydraulic pressure test (no difference)

7. Wall thickness detection 
PSL1: No measurement coverage requirements for wall thicknesses of J55 and K55;
PSL2: For wall thickness measurement and recording of J55 and K55 for full length, the surface area covered by the automatic detection system should preferably reach 25%.

8. Non-destructive testing
PSL1: No mandatory requirements for non-destructive testing of grades J55 and K55;
PSL2: All steel grades of grades J55 and K55 shall be tested using one or more of the methods specified in the standard to find that the outer and inner surfaces of the steel tube may receive the longitudinal imperfections of the horizontal L4.

9. Logo 
A bright green belt is sprayed on the J55 casing pipe, the collar is painted bright green, and a white belt is added;

Two bright green belts are sprayed on the K55 steel tube, and the collar is painted bright green with no additional ribbon.

API 5CT J55 Size Chart

Outer Diameter		Wall Thickness	Weight	Grade	Threaded	Length
in	mm	kg/m	lb/ft
4 1/2″	114.3	14.14-22.47	9.50-11.50	J55	LTC/STC/BTC	R1/R2/R3
5″	127	17.11-35.86	11.50-24.10	J55	LTC/STC/BTC	R1/R2/R3
5 1/2″	139.7	20.83-34.23	14.00-23.00	J55	LTC/STC/BTC	R1/R2/R3
6 5/8″	168.28	29.76-35.72	20.00-24.00	J55	LTC/STC/BTC	R1/R2/R3
7″	177.8	25.30-56.55	17.00-38.00	J55	LTC/STC/BTC	R1/R2/R3
7 5/8″	193.68	35.72-63.69	24.00-42.80	J55	LTC/STC/BTC	R1/R2/R3
8 5/8″	219.08	35.72-72.92	24.00-49.00	J55	LTC/STC/BTC	R1/R2/R3
9 5/8″	244.48	48.07-86.91	32.30-58.40	J55	LTC/STC/BTC	R1/R2/R3
10 3/4″	273.05	48.73-97.77	32.75-65.70	J55	LTC/STC/BTC	R1/R2/R3
11 3/4″	298.45	62.50-89.29	42.00-60.00	J55	LTC/STC/BTC	R1/R2/R3
13 3/8″	339.72	71.43-107.15	48.00-72.00	J55	LTC/STC/BTC	R1/R2/R3

API 5CT K55 Size Chart

Outer Diameter		Wall Thickness	Weight	Grade	Threaded	Length
in	mm	kg/m	lb/ft
4 1/2″	114.3	14.14-22.47	9.50-11.50	K55	LTC/STC/BTC	R1/R2/R3
5″	127	17.11-35.86	11.50-24.10	K55	LTC/STC/BTC	R1/R2/R3
5 1/2″	139.7	20.83-34.23	14.00-23.00	K55	LTC/STC/BTC	R1/R2/R3
6 5/8″	168.28	29.76-35.72	20.00-24.00	K55	LTC/STC/BTC	R1/R2/R3
7″	177.8	25.30-56.55	17.00-38.00	K55	LTC/STC/BTC	R1/R2/R3
7 5/8″	193.68	35.72-63.69	24.00-42.80	K55	LTC/STC/BTC	R1/R2/R3
8 5/8″	219.08	35.72-72.92	24.00-49.00	K55	LTC/STC/BTC	R1/R2/R3
9 5/8″	244.48	48.07-86.91	32.30-58.40	K55	LTC/STC/BTC	R1/R2/R3
10 3/4″	273.05	48.73-97.77	32.75-65.70	K55	LTC/STC/BTC	R1/R2/R3
11 3/4″	298.45	62.50-89.29	42.00-60.00	K55	LTC/STC/BTC	R1/R2/R3
13 3/8″	339.72	71.43-107.15	48.00-72.00	K55	LTC/STC/BTC	R1/R2/R3