Understanding the Distinction: Casing vs. Tubing

What is the difference between casing and tubing? Understanding the distinction between these two terms is crucial in the Oil and gas industry. Casing and tubing are both essential components used in drilling and completing oil and gas wells. While they may appear similar, they serve different purposes and have distinct characteristics.

Casing is a large–diameter Pipe that is installed in the wellbore to provide structural integrity and support the well. It is typically made of steel and comes in various sizes, Lengths, and grades. Casing is designed to withstand high pressure, prevent collapse, and protect the well from external forces. It is installed from the surface down to the target depth, forming a protective barrier between the wellbore and the surrounding formations. On the other hand, tubing is a smaller-diameter pipe that is inserted inside the casing. It is also made of steel and comes in different sizes and grades. Tubing is used to transport fluids, such as oil and gas, from the well to the surface. It provides a conduit for production and allows for the installation of various downhole equipment, such as pumps and sensors. Unlike casing, tubing is not designed to withstand high pressure or provide structural support.

API 5ct L80 casing tubingdimensions and Masses for Standard Casing and for Casing threaded with
API Round Thread and Buttress Thread
Labels a							Calculated Mass c
			Nominal linear Mass T& C b,c	Wall Thick- ness				em, Mass Gain or Loss Due to End Finishing d
		Outside Diameter			Inside Diameter	Drift Diameter	Plain- end	kg
								Round Thread		Buttress Thread
							wpe
		D	kg/m	t	D	mm	kg/m	Short	Long	RC	SCC
		mm		mm	mm
1	2	3	4	5	6	7	8	9	10	11	12
4 1/2	9.5	114.3	14.38	5.21	103.88	100.7	14.02	3.64	—	— 4.53	— 1.12
4 1/2	10.5	114.3	15.73	5.69	102.92	99.74	15.24	3.33	— 3.61	4.32	0.91
4 1/2	11.6	114.3	17.38	6.35	101.6	98.42	16.91	3.18	3.35	4.07	0.6
4 1/2	13.5	114.3	19.87	7.37	99.56	96.38	19.44	—	3.53	3.64	0.24
4 1/2	15.1	114.3	22.69	8.56	97.18	94	22.32	—
5	11.5	127	17.19	5.59	115.82	112.64	16.74	4.32	— 4.85	— 5.38	— 1.24
5	13	127	19.69	6.43	114.14	110.96	19.12	4	4.51	4.99	0.61
5	15	127	22.69	7.52	111.96	108.78	22.16	3.71	4.52	4.4	0.22
5	18	127	27.19	9.19	108.62	105.44	26.7	—	3.45	3.76	–0.62
5	21.4	127	32.13	11.1	104.8	101.62	31.73	—	3.15	3.42	–0.96
5	23.2	127	34.76	12.14	102.72	99.54	34.39	—	2.99	3.23	–1.14
5	24.1	127	36.15	12.7	101.6	98.42	35.8	—
5 1/2	14	139.7	20.91	6.2	127.3	124.12	20.41	4.6	— 5.26	— 5.71	— 0.87
5 1/2	15.5	139.7	23.48	6.98	125.74	122.56	22.85	4.36	5.31	5.41	0.58
5 1/2	17	139.7	25.72	7.72	124.26	121.08	25.13	4.14	4.5	4.84	0.45
5 1/2	20	139.7	30.05	9.17	121.36	118.18	29.52	—	4.37	4.31	-0.52
5 1/2	23	139.7	34.05	10.54	118.62	115.44	33.57	—	—	—	—
5 1/2	26.8	139.7	40.15	12.7	114.3	111.12	39.78	—	—	—	—
5 1/2	29.7	139.7	44.47	14.27	111.16	107.98	44.14	—	—	—	—
5 1/2	32.6	139.7	48.74	15.88	107.94	104.76	48.49	—	—	—	—
5 1/2	35.3	139.7	52.8	17.45	104.8	101.62	52.61	—	—	—	—
5 1/2	38	139.7	56.82	19.05	101.6	98.42	56.68	—	—	—	—
5 1/2	40.5	139.7	60.64	20.62	98.46	95.28	60.55	—	—	—	—
5 1/2	43.1	139.7	64.41	22.22	95.26	92.08	64.38	—
6 5/8	20	168.28	29.76	7.32	153.64	150.46	29.06	5.58	6.23	6.35	0.89
6 5/8	24	168.28	35.72	8.94	150.4	147.22	35.13	4.42	5.48	5.52	0.68
6 5/8	28	168.28	41.67	10.59	147.1	143.92	41.18	—	4.73	4.71	–0.75
6 5/8	32	168.28	47.62	12.06	144.16	140.98	46.46	—	4.73	4	–1.46

One key difference between casing and tubing is their size. Casing is typically larger in diameter and thicker in Wall thickness compared to tubing. This is because casing needs to withstand higher pressures and provide structural support to the well. Tubing, on the other hand, has a smaller diameter and thinner walls since it Stainless steel 316L Tube Settler for Oil Gas Treatment