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Knowledge | Petroleum Pipe Introduction


Knowledge Petroleum Pipe Introduction - Bluslot

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Explanation of special terms related to petroleum pipe 

API:It is the abbreviation of the American Petroleum Institute.
OCTG:It’s short for Oil Country Tubular Goods.
Tubing:Pipes used for oil production, gas production, water injection and acid fracturing in oil wells.
Casing:Run the drilled hole from the ground surface as a liner to prevent the collapse of the well wall. Drill pipe: a pipe used for drilling holes.
Line pipe:Pipes used to transport oil and gas.
Coupling:A cylinder body for connecting two threaded pipes and having internal threads. Coupling material: pipe used to make the coupling.
API thread:Pipe thread specified in API 5B standard, including around thread of tubing, a short round thread of casing, a long round thread of casing, trapezoid thread of casing, pipeline thread, etc.
Special button:Non API thread type with special sealing performance, connection performance, and other performance.
Invalid:Deformation, fracture, surface damage and loss of original function occur under specific service conditions. The main forms of casing failure are collapse, slippage, rupture, leakage, corrosion, adhesion, wear and so on.

Petroleum related standards 

API 5CT: casing and tubing specifications (currently the latest version is version 8)
API 5D: Specification for drill pipe (currently the latest version is version 5)
API 5L: Pipeline steel pipe specification (currently the latest edition is the 44th edition)
API 5B: Specification for processing, measurement and inspection of the casing, tubing and line pipe threads
GB / T 9711.1-1997: Technical Conditions for Delivery of Steel Pipes for Oil and Gas Industry Part 1: Grade A Steel Pipe GB / T9711.2-1999: Technical Conditions for Delivery of Steel Pipes for Oil and Gas Industry Part 2: Grade B Steel Pipe GB / T9711 .3-2005: Technical Conditions for Delivery of Steel Pipes for Oil and Gas Industry Part 3: C-Class Steel Pipes


1. Classification of tubing

Tubing is divided into flat tubing (NU), thickened tubing (EU) and integral joint tubing.
Flat tubing means that the pipe end is directly threaded without thickening and is provided with a coupling.
Thickened tubing means that after the two ends of the tubing are thickened externally, the thread is threaded and the coupling is attached.
The integral joint oil pipe means that one end passes through the inner thickened outer thread of the car and the other end passes through the outer thickened inner thread of the car, which is directly connected without a coupling.

2. The role of tubing

Extraction of oil and steam:After drilling and cementing of oil and gas wells, oil pipes are placed in the casing to extract oil and gas to the surface.

②Water injection:When the downhole pressure is not enough, inject water into the well through the tubing. 

③Steam injection:In the process of heavy oil thermal recovery, it is necessary to use insulated tubing to input steam into the well. 

④ Acidizing and fracturing:In the later period of well drilling or in order to improve the production of oil and gas wells, it is necessary to input acidizing and fracturing media or solidified substances, both of which are transported through the tubing. 

3. Steel grade of tubing

Tubing steel grades are H40, J55, N80, L80, C90, T95, P110.

N80 is divided into N80-1 and N80Q. The same point of the two is the same tensile properties. The difference between the two is the difference between the delivery state and the impact performance. When the temperature is Ar3 and the air is cooled after the tension is reduced, normalizing can be replaced by hot rolling. Impact energy and non-destructive testing are not required; N80Q must be heat treated by quenching and tempering (quenching and tempering). And non-destructive testing should be carried out.

L80 is divided into l80-1, l80-9cr, and l80-13cr. Their mechanical properties and delivery state are the same. The difference lies in the use, production difficulty and price. L80-1 is a common type, l80-9cr and l80-13cr are high corrosion resistant oil pipes, which are difficult to produce and expensive, and are usually used for heavy corrosion oil wells.

C90 and T95 are divided into type 1 and type 2, namely, c90-1, c90-2, t95-1, and t95-2. 


Classification and function of casing

The casing is a steel pipe that supports the walls of oil and gas wells. Each well will use several layers of the casing according to different drilling depths and geological conditions. Cement is used to cement the casing after it goes down the well. It is different from tubing and drill pipe and cannot be reused. It is disposable material. Therefore, the casing consumption accounts for more than 70% of all oil well pipes.

①Guide sleeve

It is mainly used for drilling in oceans and deserts to separate seawater and sand to ensure smooth drilling. The main specifications of this layer of casing are ∮762mm (30in) × 25.4mm ∮762mm (30in) × 19.06mm.

②Surface casing

It is mainly used for the first drilling, drilling the soft ground surface layer to the bedrock, in order to seal this part of the formation from collapse, it needs to be sealed with surface casing.

The main specifications of the surface casing: 508mm (20in), 406.4mm (16in), 339.73mm (13-3 / 8in), 273.05mm (10-3 / 4in), 244.48mm (9-5 / 9in), etc.The depth of the downpipe depends on the depth of the soft formation, generally 80 ~ 1500m. Its external pressure and internal pressure are not large, generally K55 steel grade or N80 steel grade.

③Technical casing

The technical casing is used in the drilling process of complex formation. When encountering collapse layer, oil layer, gas layer, water layer, leakage layer, salt gypsum layer, and other complex parts, it is necessary to run technical casing for sealing, otherwise, the drilling cannot be carried out.

Some wells are deep and complex, and the depth of well running is up to several kilometers. This kind of deep well needs several layers of technical casings. Its mechanical properties and sealing performance requirements are very high, and the steel grade used is also high. In addition to K55, N80 and P110 steel grades are more used. Some deep wells also use q125 or higher non API steel grades such as V150.

The main specifications of the technical casing are: 339.73mm (13-3 / 8in), 273.05mm (10-3 / 4in), 244.48mm (9-5 / 8in), 219.08mm (8-5 / 8in) 193.68mm ( 7-5 / 8in), 177.8mm (7in) etc. 

④Oil layer casing 

When the drilling reaches the target layer (oil and gas-bearing horizon), the oil and gas layer and the upper exposed stratum are all sealed with an oil layer casing. Inside the oil, layer casing is the oil layer. Reservoir casing has the deepest downhole depth in various casings, and its mechanical and sealing performance requirements are also the highest. Steel grades include K55, N80, P110, Q125, V150, etc. The main specifications of the oil layer casing are 177.8mm (7in), 168.28mm (6-5 / 8in), 139.7mm (5-1 / 2in), 127mm (5in), 114.3mm (4-1 / 2in) and so on. 

Drill pipe 

Drill pipe classification and function 

The square drill pipe, drill pipe, weighted drill pipe and drill collar in the drilling tool form a drill string. The drill string is the core drilling tool that drives the drill bit from the surface to the bottom of the well, and is also a passage from the surface to the bottom of the well. It has 3 main functions:

①Transmitting torque drives the drill bit to drill.

②Rely on its own weight to apply pressure to the drill bit to crush the bottom rock.

③Convey well-washing fluid, that is, the drilling mud passes through the high-pressure mud pump on the ground, drives into the inner hole of the drill string, flows into the bottom of the hole to wash the cuttings and cool the drill bit, and carries the cuttings back through the annular space between the outer surface of the drilling string and the well wall To the ground, to achieve the purpose of drilling.

The drill string must withstand various complex alternating loads during the drilling process, such as tension, compression, torsion, bending and other stresses. The inner surface must also withstand the erosion and corrosion of high-pressure mud. 

⑴Kelly bar:There are two types of square drill pipes: square and hexagonal. China’s oil drill pipes usually use a square drill pipe for each set of drill strings.

Its specifications are: 63.5mm (2-1 / 2in), 88.9mm (3-1 / 2in), 107.95mm (4-1 / 4in), 133.35mm (5-1 / 4in), 152.4mm (6in) etc. 

Usually, the length is 12 ~ 14.5m. 

⑵Drill pipe:The drill rod is the main tool for drilling and is connected to the lower end of the kelly rod. As the drilling continues to deepen, the drill rod continues to lengthen the drill string one by one.

The specifications of the drill rod are: 60.3mm (2-3 / 8in), 73.03mm (2-7 / 8in), 88.9mm (3-1 / 2in), 114.3mm (4-1 / 2in), 127mm (5in), 139.7mm (5-1 / 2in), etc. 

⑶Heavy drill pipe:The weighted drill pipe is a transition tool connecting the drill pipe and the drill collar, which can improve the stress condition of the drill pipe and increase the pressure on the drill bit. The main specifications of the weighted drill pipe are 88.9mm (3-1 / 2in) and 127mm (5in).

⑷Drill collar:The drill collar is connected to the lower part of the drill string. It is a very thick-walled tube with high rigidity, which exerts pressure on the broken rock of the drill bit and can play a guiding role when straightening the well.Common specifications of drill collars are: 158.75mm (6-1 / 4in), 177.85mm (7in), 203.2mm (8in), 228.6mm (9in), etc. 

Line pipe 

Line pipe classification

Line pipe is the abbreviation of steel pipe used for pipeline transportation of petroleum, refined oil, natural gas and water in the oil and gas industry.

The pipelines for transporting oil and gas are mainly divided into three types: mainline pipeline, branch line pipeline, and urban pipeline network. The main specifications of the mainline pipeline are ∮406 ~ 1219mm, the wall thickness is 10 ~ 25mm, and the steel grade is X42 ~ X80.

The general specifications of feeder pipelines and urban pipeline networks are ∮114 ~ 700mm, wall thickness 6 ~ 20mm, and steel grades are X42 ~ X80. 

There are welded steel pipes and seamless steel pipes for pipelines, and more welded steel pipes are used than seamless steel pipes. 

Line pipe standard

The standard implemented by line pipe is API 5L “Code for Pipe Pipe”, but China issued two national standards for line pipes in 1997: GB / T9711.1-1997 “Technical Conditions for Delivery of Steel Pipes for Oil and Gas Industry Part One: Class A steel pipe》and GB / T9711.2-1997 “Technical Conditions for Delivery of Steel Pipes for Petroleum and Natural Gas Industry Part II: Grade B Steel Pipe”.

These 2 standards are equivalent to API 5L, and many domestic users require the supply according to these 2 national standards. 

About PSL1 and PSL2

PSL is the abbreviation of the product specification level.

The product specification level of the pipeline is divided into PSL1 and PSL2, and the quality level is also divided into PSL1 and PSL2.

PSL1 is higher than PSL2. These two specification levels are not only different in inspection requirements, but also different in chemical composition and mechanical property requirements. Therefore, when ordering according to API 5L, the terms in the contract must indicate the product specification level, i.e. PSL1 or PSL2, in addition to the normal indicators such as specification and steel grade. 

PSL2 is stricter than PSL1 in chemical composition, tensile property, impact energy, nondestructive testing, and other indexes. 

Water pressure and nondestructive requirements of the pipeline 

The water pressure test should be carried out one by one for the pipeline, and the standard does not allow the replacement of water pressure without damage, which is also a big difference between the API standard and the Chinese standard. 

PSL1 does not require NDT, and PSL2 shall be NDT one by one.