Product Category

Projects

Casing

Keywords	Casing and Tubing, Oil Casing, Gas Casing, Casing Pipe, API 5CT Casing, Seamless Oil Casing
Size Range	Casing OD: 4 1/2 inch ~ 20 inch (48.26mm ~ 508mm)
	Tubing OD: 48.26mm ~ 114.3mm
	Nominal Weight: 9.5 ppf ~ 169 ppf
	Standard Length: R1, R2, R3
Standards & Steel Grades	(API 5CT) H40, J55, K55, M65, N80-1, N80-Q, L80 Type 1, L80 9Cr, L80 13Cr, C90, T95, P110, Q125
Connections	Casing Thread: SC (Short Round Thread), LC (Long Round Thread), BC (Buttress Thread)
Connections	Tubing Type: NU (Non-upset), EU (External Upset), IJ (Integral Joint)
Color Band	Color Band Marking Standard API 5CT color band identification (Green, White, Blue, Yellow) for accurate steel grade classification

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Introduction
Specs & Sizes
Material Properties
Process & Finishing
Test & QC
FAQ

Introduction

API 5CT is the unified international standard for seamless casing and tubing used in oil and gas wells, specifying technical requirements including chemical composition, mechanical properties, manufacturing tolerance, thread connection, inspection test and delivery conditions for petroleum steel pipes.

Material Steel Grades & Applicable Working Conditions：
H40, J55, K55: Low-to-medium strength carbon steel grades, suitable for shallow oil & gas wells with low pressure and mild corrosion environments. They are cost-effective for conventional shallow well projects without severe acid gas erosion.

M65, N80 (Type 1, Q): Medium-strength carbon steel casing for medium-depth conventional wells under moderate pressure. N80 Q features improved quenched and tempered mechanical performance for higher tensile and collapse resistance than standard N80 Type 1.

L80 (9Cr, 13Cr): Corrosion-resistant alloy steel grades. 9Cr and 13Cr contain chromium elements to resist corrosion caused by carbon dioxide and trace hydrogen sulfide in formation fluid, specially applied to mildly sour oil and gas wells.

C90, T95, P110, Q125: High-strength premium steel grades with excellent collapse resistance, tensile strength and internal pressure resistance. Designed for deep wells, ultra-deep wells and harsh service environments featuring high pressure and severe corrosion, ideal for high-depth high-pressure sour gas wells.

All API 5CT casing and tubing are marked with standardized color bands on pipe ends for quick identification of steel grades, fully following API 5CT marking rules. Each steel grade corresponds to exclusive color codes, enabling field workers to distinguish pipe specifications without checking documents.

Color coding serves core functions:
Rapid grade identification: Differentiate H40, J55, N80, L80, P110, Q125 and corrosion-resistant 9Cr/13Cr alloy steel at a glance;
Avoid mixing up pipes during transportation, storage and downhole running;
Simplify inventory management and on-site construction inspection.

All color band marking is firm, wear-resistant and not easy to fall off under long-term outdoor storage. The matching color code chart clearly displays the corresponding color bands for every casing and tubing grade, acting as an intuitive reference for warehouse and oilfield operation teams.

Colour Code of Casing and Tubing

Grade	Colour Code Pipe (text)	Heat Treatment	Characteristics and Recommendation
J55		Normalized, Normalized and Tempered or quenched and Tempered	Tubing & Casing for general service
K55		Normalized, Normalized and Tempered or quenched and Tempered	Casing for general service
N80 Type 1		Normalized or Normalized and Tempered	Tubing & Casing for general service
N80 Type Q		Quenched and Tempered	Tubing & Casing for general service
L80 Type 1		Quenched and Tempered	Tubing & Casing with controlled yield range for sour well service
L80 9 Cr		Quenched and Tempered	Tubing & Casing for oil & gas wells affected by CO2 corrosion
L80 13 Cr		Quenched and Tempered	Tubing & Casing for oil & gas wells affected by CO2 corrosion
C90 Type 1		Quenched and Tempered	Hight strength Tubing & Casing with controlled yield range for service in hydrogen sulphide environments
R95		Quenched and Tempered	High strength Tubing & Casing with controlled yield range
T95 Type 1		Quenched and Tempered	High strength Tubing & Casing with controlled yield range for service in hydrogen sulphide environments
C110		Quenched and Tempered	High strength Casing with controlled yield range for service in hydrogen sulphide environments
P110		Quenched and Tempered	High strength Tubing & Casing for high pressure service
Q125 Type 1		Quenched and Tempered	Casing for deep well service

Specs & Sizes

The Casing and Tubing dimension table covers all standard OD sizes from 4 1/2" to 20" with matched nominal weights and standard R1/R2/R3 lengths. All data complies with API 5CT, providing intuitive size reference for oil well design and procurement. The Casing and Tubing dimension tolerance table is attached to specify permissible deviations of outer diameter, wall thickness, length and weight. All data complies with API 5CT, providing intuitive size and tolerance reference for oil well design and procurement.

Dimension Tolerances:

Casing Pipe	Item / Part	Tolerance
Outside Diameter	Pipe Body	D≤101.60mm, ±0.79mm
	Pipe Body	D≥114.30mm, +1.0%, -0.5%D
	Coupling	±1%D
Wall Thickness		0, -12.5%t
Weight	Single Lengths	+6.5%, -3.5%
	Carload Lots or Order Quantity	≥18144 kg (40000lb), 0, -1.75%
	Carload Lots or Order Quantity	< 18144 kg (40000lb), 0, -3.5%

Dimensions table for casing

DN	O.D. Inch	O.D. mm	Weight lb/ft	Weight kg/m	W.T. Inch	W.T. mm	H40	J55 / K55	L80	N80	C90 / T95	P110
4 1/2	4.5	114.3	9.5	14.14	0.205	5.21	PS	PS	–	–	–	–
			10.5	15.63	0.224	5.69	–	PSB	–	–	–	–
			11.6	17.26	0.25	6.35	–	PSLB	PLB	PLB	PLB	PLB
			13.5	20.09	0.29	7.37	–	–	PLB	PLB	PLB	PLB
			15.1	22.47	0.337	9.56	–	–	–	–	–	PLB
5	5	127	11.5	17.11	0.22	5.59	–	PS	–	–	–	–
			13	19.35	0.253	6.43	–	PSLB	–	–	–	–
			15	22.32	0.296	7.52	–	PSLB	PLB	PLB	PLBE	PLB
			18	26.79	0.362	9.19	–	–	PLB	PLB	PLBE	PLB
			21.4	31.85	0.437	11.1	–	–	PLB	PLB	PLB	PLB
			23.2	34.53	0.478	12.14	–	–	–	–	PLB	–
			24.1	35.86	0.5	12.7	–	–	–	–	PLB	–
5 1/2	5.5	139.7	14	20.83	0.244	6.2	PS	PS	–	–	–	–
			15.5	23.07	0.275	6.98	–	PSLB	–	–	–	–
			17	25.3	0.304	7.72	–	PSLB	PLB	PLB	PLBE	PLB
			20	29.76	0.361	9.17	–	–	PLB	PLB	PLBE	PLB
			23	34.23	0.415	10.54	–	–	PLB	PLB	PLBE	PLB
			26.8	39.88	0.5	12.7	–	–	–	–	–	–
			29.7	44.2	0.562	14.27	–	–	–	–	–	–
			32.6	48.51	0.625	15.88	–	–	–	–	–	–
			35.3	52.53	0.687	17.45	–	–	–	–	–	–
			38	56.55	0.75	19.05	–	–	–	–	–	–
			40.5	60.27	0.812	20.62	–	–	–	–	–	–
			43.1	64.14	0.875	22.22	–	–	–	–	–	–
6 5/8	6.625	168.28	20	29.76	0.288	7.32	PS	PSLB	–	–	–	–
			24	35.72	0.352	8.94	–	PSLB	PLB	PLB	PLBE	PLB
			28	41.67	0.417	10.59	–	–	PLB	PLB	PLBE	PLB
			32	47.62	0.475	12.06	–	–	PLB	PLB	PLBE	PLB
7	7	177.8	17	25.3	0.231	5.87	PS	–	–	–	–	–
			20	29.76	0.272	6.91	PS	PS	–	–	–	–
			23	34.23	0.317	8.05	–	PSLB	PLB	PLB	PLBE	–
			26	38.69	0.362	9.19	–	PSLB	PLB	PLB	PLBE	PLB
			29	43.16	0.408	10.36	–	–	PLB	PLB	PLBE	PLB
			32	47.62	0.453	11.51	–	–	PLB	PLB	PLBE	PLB
			35	52.09	0.498	12.65	–	–	PLB	PLB	PLBE	PLB
			38	56.55	0.54	13.72	–	–	PLB	PLB	PLBE	PLB
			42.7	63.54	0.625	15.88	–	–	–	–	–	–
			46.4	69.05	0.687	17.45	–	–	–	–	–	–
			50.1	74.56	0.75	19.05	–	–	–	–	–	–
			53.6	79.77	0.812	20.62	–	–	–	–	–	–
			57.1	84.97	0.875	22.22	–	–	–	–	–	–
7 5/8	7.625	193.68	24	35.72	0.3	7.62	PS	–	–	–	–	–
			26.4	39.29	0.328	8.33	–	PSLB	PLB	PLB	PLBE	PLB
			29.7	44.2	0.375	9.52	–	–	PLB	PLB	PLBE	PLB
			33.7	50.15	0.43	10.92	–	–	PLB	PLB	PLBE	PLB
			39	58.05	0.5	12.7	–	–	PLB	PLB	PLBE	PLB
			42.8	63.69	0.562	14.27	–	–	PLB	PLB	PLB	PLB
			45.3	67.41	0.595	15.11	–	–	PLB	PLB	PLB	PLB
			47.1	70.09	0.625	15.88	–	–	PLB	PLB	PLB	PLB
			51.2	76.19	0.687	17.45	–	–	–	–	–	–
			55.3	80.3	0.75	19.05	–	–	–	–	–	–
8 5/8	8.625	219.08	24	35.72	0.264	6.71	–	PS	–	–	–	–
			28	41.62	0.304	7.72	PS	–	–	–	–	–
			32	47.62	0.352	8.94	PS	PSLB	–	–	–	–
			36	53.57	0.4	10.16	–	PSLB	PLB	PLB	PLBE	PLB
			40	59.53	0.45	11.43	–	–	PLB	PLB	PLBE	PLB
			44	65.48	0.5	12.7	–	–	PLB	PLB	PLBE	PLB
			49	72.92	0.557	14.15	–	–	PLB	PLB	PLBE	PLB
9 5/8	9.625	244.48	32.3	48.07	0.312	7.92	PS	–	–	–	–	–
			36	53.57	0.352	8.94	PS	PSLB	–	–	–	–
			40	59.53	0.395	10.03	–	PSLB	PLB	PLB	PLBE	–
			43.5	64.73	0.435	11.05	–	–	PLB	PLB	PLBE	PLB
			47	69.94	0.472	11.99	–	–	PLB	PLB	PLBE	PLB
			53.5	79.62	0.545	13.84	–	–	PLB	PLB	PLBE	PLB
			58.4	86.91	0.595	15.11	–	–	PLB	PLB	PLB	PLB
			59.4	88.4	0.609	15.47	–	–	–	–	–	–
			64.9	96.58	0.672	17.07	–	–	–	–	–	–
			70.3	104.62	0.734	18.64	–	–	–	–	–	–
			75.6	112.5	0.797	20.24	–	–	–	–	–	–
10 3/4	10.75	273.05	32.75	48.74	0.279	7.09	PS	–	–	–	–	–
			40.5	60.27	0.35	8.89	PS	PSB	–	–	–	–
			45.5	67.71	0.4	10.16	–	PSB	–	–	–	–
			51	75.9	0.45	11.43	–	PSB	PSB	PSB	PSBE	PSB
			55.5	82.59	0.495	12.57	–	–	PSB	PSB	PSBE	PSB
			60.7	90.33	0.545	13.84	–	–	–	–	PSBE	PSB
			65.7	97.77	0.595	15.11	–	–	–	–	PSB	PSB
			73.2	108.93	0.672	17.07	–	–	–	–	–	–
			79.2	117.86	0.734	18.64	–	–	–	–	–	–
			85.3	126.94	0.797	20.24	–	–	–	–	–	–
11 3/4	11.75		42	62.5	0.333	8.46	PS	–	–	–	–	–
			47	69.94	0.375	20.24	–	–	–	–	–	–
			54	80.36	0.435	8.46	–	–	–	–	–	–
			60	89.29	0.489	9.53	–	–	–	–	–	–
			65	96.73	0.534	11.05	–	–	–	–	–	–
			71	105.66	0.582	14.42	–	–	–	–	–	–
13 3/8	13.375	339.73	48	71.43	0.33	8.38	PS	–	–	–	–	–
			54.5	81.1	0.38	9.65	–	PSB	–	–	–	–
			61	90.78	0.43	10.92	–	PSB	–	–	–	–
			68	101.19	0.48	12.19	–	PSB	PSB	PSB	PSB	PSB
			72	107.15	0.514	13.06	–	–	PSB	PSB	PSB	PSB
16	16	406.4	65	96.73	0.375	9.53	PS	–	–	–	–	–
			75	111.61	0.438	11.13	–	PSB	–	–	–	–
			84	125.01	0.495	12.57	–	PSB	–	–	–	–
			109	162.21	0.656	16.66	–	P	P	P	–	P
18 5/8	18.625	473.08	87.5	130.21	0.435	11.05	PS	PSB	–	–	–	–
20	20	508	94	139.89	0.438	11.13	PSL	PSLB	–	–	–	–
			106.5	158.49	0.5	12.7	–	PSLB	–	–	–	–
			133	197.93	0.635	16.13	–	PSLB	–	–	–	–
P——Plain;S——Short-thread; L——Long-thread; B——Buttress thread;E——Extreme thread

Dimensions table for tubing

DN	O.D. Inch	O.D. mm	Weight lb/ft	Weight kg/m	W.T. Inch	W.T. mm	H40	J55 / K55	L80	N80	C90 / T95	P110
4 1/2	4.5	114.3	9.5	14.14	0.205	5.21	PS	PS	–	–	–	–
			10.5	15.63	0.224	5.69	–	PSB	–	–	–	–
			11.6	17.26	0.25	6.35	–	PSLB	PLB	PLB	PLB	PLB
			13.5	20.09	0.29	7.37	–	–	PLB	PLB	PLB	PLB
			15.1	22.47	0.337	9.56	–	–	–	–	–	PLB
5	5	127	11.5	17.11	0.22	5.59	–	PS	–	–	–	–
			13	19.35	0.253	6.43	–	PSLB	–	–	–	–
			15	22.32	0.296	7.52	–	PSLB	PLB	PLB	PLBE	PLB
			18	26.79	0.362	9.19	–	–	PLB	PLB	PLBE	PLB
			21.4	31.85	0.437	11.1	–	–	PLB	PLB	PLB	PLB
			23.2	34.53	0.478	12.14	–	–	–	–	PLB	–
			24.1	35.86	0.5	12.7	–	–	–	–	PLB	–
5 1/2	5.5	139.7	14	20.83	0.244	6.2	PS	PS	–	–	–	–
			15.5	23.07	0.275	6.98	–	PSLB	–	–	–	–
			17	25.3	0.304	7.72	–	PSLB	PLB	PLB	PLBE	PLB
			20	29.76	0.361	9.17	–	–	PLB	PLB	PLBE	PLB
			23	34.23	0.415	10.54	–	–	PLB	PLB	PLBE	PLB
			26.8	39.88	0.5	12.7	–	–	–	–	–	–
			29.7	44.2	0.562	14.27	–	–	–	–	–	–
			32.6	48.51	0.625	15.88	–	–	–	–	–	–
			35.3	52.53	0.687	17.45	–	–	–	–	–	–
			38	56.55	0.75	19.05	–	–	–	–	–	–
			40.5	60.27	0.812	20.62	–	–	–	–	–	–
			43.1	64.14	0.875	22.22	–	–	–	–	–	–
6 5/8	6.625	168.28	20	29.76	0.288	7.32	PS	PSLB	–	–	–	–
			24	35.72	0.352	8.94	–	PSLB	PLB	PLB	PLBE	PLB
			28	41.67	0.417	10.59	–	–	PLB	PLB	PLBE	PLB
			32	47.62	0.475	12.06	–	–	PLB	PLB	PLBE	PLB
7	7	177.8	17	25.3	0.231	5.87	PS	–	–	–	–	–
			20	29.76	0.272	6.91	PS	PS	–	–	–	–
			23	34.23	0.317	8.05	–	PSLB	PLB	PLB	PLBE	–
			26	38.69	0.362	9.19	–	PSLB	PLB	PLB	PLBE	PLB
			29	43.16	0.408	10.36	–	–	PLB	PLB	PLBE	PLB
			32	47.62	0.453	11.51	–	–	PLB	PLB	PLBE	PLB
			35	52.09	0.498	12.65	–	–	PLB	PLB	PLBE	PLB
			38	56.55	0.54	13.72	–	–	PLB	PLB	PLBE	PLB
			42.7	63.54	0.625	15.88	–	–	–	–	–	–
			46.4	69.05	0.687	17.45	–	–	–	–	–	–
			50.1	74.56	0.75	19.05	–	–	–	–	–	–
			53.6	79.77	0.812	20.62	–	–	–	–	–	–
			57.1	84.97	0.875	22.22	–	–	–	–	–	–
7 5/8	7.625	193.68	24	35.72	0.3	7.62	PS	–	–	–	–	–
			26.4	39.29	0.328	8.33	–	PSLB	PLB	PLB	PLBE	PLB
			29.7	44.2	0.375	9.52	–	–	PLB	PLB	PLBE	PLB
			33.7	50.15	0.43	10.92	–	–	PLB	PLB	PLBE	PLB
			39	58.05	0.5	12.7	–	–	PLB	PLB	PLBE	PLB
			42.8	63.69	0.562	14.27	–	–	PLB	PLB	PLB	PLB
			45.3	67.41	0.595	15.11	–	–	PLB	PLB	PLB	PLB
			47.1	70.09	0.625	15.88	–	–	PLB	PLB	PLB	PLB
			51.2	76.19	0.687	17.45	–	–	–	–	–	–
			55.3	80.3	0.75	19.05	–	–	–	–	–	–
8 5/8	8.625	219.08	24	35.72	0.264	6.71	–	PS	–	–	–	–
			28	41.62	0.304	7.72	PS	–	–	–	–	–
			32	47.62	0.352	8.94	PS	PSLB	–	–	–	–
			36	53.57	0.4	10.16	–	PSLB	PLB	PLB	PLBE	PLB
			40	59.53	0.45	11.43	–	–	PLB	PLB	PLBE	PLB
			44	65.48	0.5	12.7	–	–	PLB	PLB	PLBE	PLB
			49	72.92	0.557	14.15	–	–	PLB	PLB	PLBE	PLB
9 5/8	9.625	244.48	32.3	48.07	0.312	7.92	PS	–	–	–	–	–
			36	53.57	0.352	8.94	PS	PSLB	–	–	–	–
			40	59.53	0.395	10.03	–	PSLB	PLB	PLB	PLBE	–
			43.5	64.73	0.435	11.05	–	–	PLB	PLB	PLBE	PLB
			47	69.94	0.472	11.99	–	–	PLB	PLB	PLBE	PLB
			53.5	79.62	0.545	13.84	–	–	PLB	PLB	PLBE	PLB
			58.4	86.91	0.595	15.11	–	–	PLB	PLB	PLB	PLB
			59.4	88.4	0.609	15.47	–	–	–	–	–	–
			64.9	96.58	0.672	17.07	–	–	–	–	–	–
			70.3	104.62	0.734	18.64	–	–	–	–	–	–
			75.6	112.5	0.797	20.24	–	–	–	–	–	–
10 3/4	10.75	273.05	32.75	48.74	0.279	7.09	PS	–	–	–	–	–
			40.5	60.27	0.35	8.89	PS	PSB	–	–	–	–
			45.5	67.71	0.4	10.16	–	PSB	–	–	–	–
			51	75.9	0.45	11.43	–	PSB	PSB	PSB	PSBE	PSB
			55.5	82.59	0.495	12.57	–	–	PSB	PSB	PSBE	PSB
			60.7	90.33	0.545	13.84	–	–	–	–	PSBE	PSB
			65.7	97.77	0.595	15.11	–	–	–	–	PSB	PSB
			73.2	108.93	0.672	17.07	–	–	–	–	–	–
			79.2	117.86	0.734	18.64	–	–	–	–	–	–
			85.3	126.94	0.797	20.24	–	–	–	–	–	–
11 3/4	11.75		42	62.5	0.333	8.46	PS	–	–	–	–	–
			47	69.94	0.375	20.24	–	–	–	–	–	–
			54	80.36	0.435	8.46	–	–	–	–	–	–
			60	89.29	0.489	9.53	–	–	–	–	–	–
			65	96.73	0.534	11.05	–	–	–	–	–	–
			71	105.66	0.582	14.42	–	–	–	–	–	–
13 3/8	13.375	339.73	48	71.43	0.33	8.38	PS	–	–	–	–	–
			54.5	81.1	0.38	9.65	–	PSB	–	–	–	–
			61	90.78	0.43	10.92	–	PSB	–	–	–	–
			68	101.19	0.48	12.19	–	PSB	PSB	PSB	PSB	PSB
			72	107.15	0.514	13.06	–	–	PSB	PSB	PSB	PSB
16	16	406.4	65	96.73	0.375	9.53	PS	–	–	–	–	–
			75	111.61	0.438	11.13	–	PSB	–	–	–	–
			84	125.01	0.495	12.57	–	PSB	–	–	–	–
			109	162.21	0.656	16.66	–	P	P	P	–	P
18 5/8	18.625	473.08	87.5	130.21	0.435	11.05	PS	PSB	–	–	–	–
20	20	508	94	139.89	0.438	11.13	PSL	PSLB	–	–	–	–
			106.5	158.49	0.5	12.7	–	PSLB	–	–	–	–
			133	197.93	0.635	16.13	–	PSLB	–	–	–	–

Material Properties

Manufactured in full compliance with API 5CT, our oil casing and tubing feature precisely controlled carbon and alloy chemical compositions. Every steel grade has unified standardized mechanical metrics covering yield strength, tensile strength, elongation and collapse resistance applicable to both casing and tubing. Corrosion-resistant L80-9Cr and L80-13Cr grades are formulated with chromium alloy to resist CO₂ and hydrogen sulfide erosion; high-strength grades offer outstanding load-bearing performance for deep and high-pressure well conditions. Both casing and tubing undergo full mandatory chemical analysis and physical performance testing before delivery.

Tensile Properties and Hardness

Category	Grade	Yield Strength Min. (psi)	Yield Strength Max. (psi)	Tensile Strength Min. (psi)	Elongation (%)	Hardness (HRC)
API 5CT	H-40	40,000	80,000	60,000	API formula	–
	J-55	55,000	80,000	75,000		–
	K-55	55,000	80,000	95,000		–
Deep Well Service DE	NT-80DE	80,000	110,000	100,000		–
High Collapse-General HE	NT-55HE	55,000	95,000	95,000		≤22
	NT-80HE	80,000	110,000	100,000		≤22
	NT-95HE	95,000	125,000	110,000		≤31
	NT-110HE	110,000	140,000	125,000		–
High Collapse-High Toughness LHE	NT-80LHE	80,000	95,000	95,000		≤22

Chemical Composition of casing pipe

Standard	Grade	Chemical compositions ( %)
API SPEC 5CT 5CT	J55	C	Si	Mn	P	S	Cr	Ni	Cu	Mo	V
	K55	0.34 ~ 0.39	0.20 ~ 0.35	1.25 ~ 1.50	≤0.020	≤0.015	≤0.15	≤0.20	≤0.20	/	/
	N80	0.34 ~ 0.38	0.20 ~ 0.35	1.45 ~ 1.70	≤0.020	≤0.015	≤0.15	/	/	/	0.11 ~ 0.16
	L80	0.15 ~ 0.22	≤1.00	0.25 ~ 1.00	≤0.020	≤0.010	12.0 ~ 14.0	≤0.20	≤0.20	/	/
	P110	0.26 ~ 0.395	0.17 ~ 0.37	0.40 ~ 0.70	≤0.020	≤0.010	0.80 ~ 1.10	≤0.20	≤0.20	0.15 ~ 0.25	≤0.08

Mechanical properties of casing pipe

Grade	Type	Total elongation under load (%)	Yield strength (min)	Yield strength (max)	Tensile strength min Mpa	Hardness Max (HRC)	Hardness Max (HBW)
J55	-	0.5	379	552	517	-	-
K55	-	0.5	379	552	655	-	-
N80	1	0.5	552	758	689	-	-
N80	Q	0.5	552	758	689	-	-
L80	1	0.5	552	655	655	23	241
L80	9Cr	0.5	552	655	655	23	241
L80	13Cr	0.5	552	655	655	23	241
C90	-	0.5	621	724	689	25.4	255
C95	-	0.5	655	758	724	-	-
T95	-	0.5	655	758	724	25.4	255
P110	-	0.6	758	965	862	-	-
Q125	All	0.65	862	1034	931	-	-

Process & Finishing

Our API 5CT casing and tubing are fully manufactured in strict compliance with global API standards. Beyond standard specifications, we independently develop proprietary steel grades tailored for extreme downhole environments, including sour service, high-collapse resistance, chrome alloy, and CRA working conditions. This customized grade system enables us to deliver targeted, optimal solutions for customers’ unique well designs and complex reservoir requirements.

All casing and tubing products are produced under ultra-stringent industrial quality standards. Our factory holds ISO 9001 global quality certification, executing unified quality policies and a full-cycle rigorous quality management system to ensure consistent, reliable pipe performance for oilfield applications.
Process-of-casing-and-tubing-1 Process-of-casing-and-tubing-2

1. Precision Steelmaking We implement professional degassing and desulfurization treatment during steelmaking, effectively reducing non-metallic inclusions and purifying steel microstructure. The process produces ultra-clean steel with excellent surface finish and stable mechanical foundation for subsequent pipe forming.

2. Fine-Grain Hot Rolling Adopting advanced hot rolling technology, we produce hot-rolled coils with uniform fine grain structure and ultra-high dimensional accuracy. This procedure guarantees consistent wall thickness, roundness and overall structural stability of finished casing and tubing.

3. Stable Spiral Looper Feeding Equipped with precision spiral looper equipment, the production line provides continuous, steady coil feeding for downstream edge milling, pipe forming and welding procedures, avoiding tension deviation and ensuring unified pipe forming quality.

4. Heavy-Duty Forming Stands High-rigidity forming stands accurately shape steel coils into standard pipes, covering a complete range of outer diameters and wall thickness specifications. The molding process ensures uniform stress distribution and qualified roundness for all casing and tubing products.

5. Intelligent HF Welding & Real-Time Monitoring We adopt NSSMC independently developed welding condition monitoring and control system for high-frequency welding. The intelligent system stabilizes welding parameters and generates high-quality, defect-free weld seams. All welds undergo 100% ultrasonic real-time inspection to eliminate hidden welding flaws.

6. Weld Seam Precision Heat Treatment Targeted heat treatment is performed exclusively on welding zones. Optical sensors accurately locate weld positions for precise thermal processing, stabilizing weld microstructure and unifying the mechanical properties of weld seams and base metal. Combined with ultrasonic and hydrostatic testing, this process ensures integral pipe body consistency.

7. Full-Coverage Non-Destructive Testing (NDT) Every single casing and tubing pipe undergoes comprehensive full-length, full-surface non-destructive testing. Systematic NDT inspection completely detects internal and surface defects, ensuring 100% structural integrity of finished pipes.

8. Automatic Comprehensive Dimension Inspection High-precision automatic inspection equipment performs full-range dimensional and appearance checks on each pipe, verifying outer diameter, wall thickness, length, straightness and surface quality to meet API 5CT tolerance standards.

9. Whole-Process Monitoring & Traceability System Online computer systems monitor and record every production procedure in real time. All manufacturing parameters, test data and processing records are permanently stored, supporting full quality traceability and customizable data reporting for global oilfield procurement and third-party audits.

10. Standardized Automatic Marking Automatic stencilling and die-stamping equipment complete standardized permanent marking for each pipe, including steel grade, size, standard, batch number and certification information, ensuring clear identification and global project adaptability.

Test & QC

All casing and tubing undergoes strict full inspection in accordance with API 5CT standard before delivery, covering raw material, semi-finished and finished pipe tests:
1)Raw material inspection: Chemical composition analysis of steel billets, surface & internal defect check
2)Dimensional inspection: OD, wall thickness, length, weight tolerance, thread dimension & thread profile detection
3)Mechanical performance test: Tensile test, yield strength, hardness, impact test, flattening test
Pressure test: Full-length hydrostatic pressure test to verify burst resistance
4)Non-destructive testing (NDT): Whole-body ultrasonic flaw detection for internal cracks, laminations and inclusions; magnetic particle inspection for surface defects
Thread inspection: Torque test, sealing performance inspection for couplings

We provide complete official certification documents for customs clearance, oilfield acceptance and project tender:
1)Mill Test Certificate (MTC / Material Test Certificate) Includes full heat number, steel grade, chemical composition, mechanical test data, hydrostatic test results and NDT records, fully traceable to raw steel billets.
2)API Monogram Certificate Our factory holds official API monogram license; all pipes are printed with API monogram marking as required by API 5CT.
3)Third-party inspection certificate (optional) Accept authorized third-party inspection such as SGS, BV, TÜV upon customer request, with independent test reports issued.
4)Standard shipping documents Commercial invoice, packing list, bill of lading, quality certificate for export clearance.

FAQ

Q1: What are oil casing and tubing pipes?

A1: Casing and tubing are API 5CT standard OCTG seamless steel pipes, serving as indispensable core components for oil and gas well drilling and completion.Large-diameter cemented pipes fixed in boreholes, used to stabilize wellbores, prevent formation collapse and isolate underground water and impurities.Precision inner pipeline installed inside casing strings, acting as a dedicated channel for transporting subsurface oil and gas to the surface.Both products adopt high-strength steel with a minimum yield strength of 35,000 psi to resist complex downhole loads, covering standard outer diameters from 4.5″ to 36″ for all well construction scenarios.

Q2: What is API 5CT standard and core specifications?

A2: API 5CT (ISO 13680) is the global unified technical standard for oilfield casing and tubing, covering material, mechanical, dimensional, thread and full inspection specifications.Available steel grades: J55, K55, N80-1, N80-Q, L80-1, L80-9Cr, L80-13Cr, C95, P110.Thread types: Standard API threads include STC, LTC, BTC, NUE, EUE; premium threads include VAM, VAM TOP, NEW VAM.Dimensional range: Outer diameter 114.3–508 mm, wall thickness 5.21–16.13 mm.

Q3: What are the classifications and functions of casing & tubing strings?

Conductor casing: 18″–36″ OD, the outermost barrier for structural support and groundwater pollution prevention.
Surface casing: Mainstream size 13 3/8″, protects freshwater formations, prevents blowouts and supports wellhead & BOP equipment.
Intermediate casing: Optional transitional casing for complex geological conditions and deep well projects.
Production casing & liner: Production casing stabilizes reservoirs and controls downhole pressure; production liner reduces costs via partial-depth installation.
Tubing function: Installed inside finished casing to form an independent sealed flow channel for long-term oil and gas production.

Q4: What steel grades are available and their applicable well conditions?

Shallow well grades (H40, J55, K55): Cost-effective for shallow, low-pressure and mild-corrosion conventional wells.
Medium-depth well grades (M65, N80-1, N80-Q): Balanced strength and stability for medium-pressure regular oil and gas wells.
Sour service grades (L80, L80-9Cr, L80-13Cr): Chromium-alloyed anti-corrosion pipes for CO₂ and H₂S acidic downhole environments.
Deep HPHT well grades (C90, T95, P110, Q125): Ultra-high-strength grades for ultra-deep, high-pressure and harsh corrosive oilfield conditions.

Q5: What thread connection types are supplied for casing and tubing?

A5: Standard API threads: Including STC, LTC, BTC, NUE, EUE, featuring stable sealing and cost efficiency for shallow and medium-depth conventional wells.Premium connection threads: Including VAM, VAM TOP, NEW VAM, with excellent gas tightness and tensile resistance for HPHT wells and deepwater complex projects.

Q6: How are casing and tubing installed in oil and gas wells?

Casing assembly: Assemble individual pipes into tapered strings with decreasing diameters through threaded couplings.
Casing running: Complete single-section drilling, withdraw drill string and lower casing into the borehole.
Casing cementing: Pump cement slurry to fill the annular space for permanent fixation, and continue drilling after cement solidification.
Tubing installation: Run production tubing inside cemented casing after well completion to form a fully enclosed and safe production system.

Q7: What quality inspection standards apply to your casing and tubing?

Material & mechanical testing: Conduct chemical composition analysis and tests for tensile strength, yield strength, hardness and impact resistance.
Pressure & NDT inspection: Perform full-length hydrostatic pressure testing and ultrasonic & electromagnetic non-destructive flaw detection.
Dimensional calibration: Precisely inspect outer diameter, wall thickness, weight and thread tolerance to meet API 5CT tolerance standards.
Certification support: Provide traceable MTC certificates, official API monogram, and optional SGS, BV, TÜV third-party inspection reports.

Q8: What are the core functions of casing and tubing in well operation?

Wellbore protection: Casing bears complex downhole pressure and tension, stabilizes boreholes and prevents formation collapse.
Formation isolation: Casing isolates high-pressure formations and avoids cross-contamination between groundwater and crude oil.
Leakage prevention: Casing eliminates underground fluid leakage and reserves stable space for downhole equipment installation.
Production transmission: Tubing acts as an independent transmission pipeline to deliver oil and gas to the surface, and protects casing from fluid erosion to extend well service life.