Drill Pipe

Drilling is the first phase of a wellbore, followed by casing, where the wellbore is lined with an outer tube, and lastly, tubing, which involves transporting oil and gas to the surface.

Drilling uses drill pipes to turn the drill bit, enabling it to cut into soil and rock to reach the mineral deposits. Casing makes use of a steel pipe cemented in place which prevents the wellbore from collapsing. In the production phase of the well, a tubing is placed inside the casing to move fluids to the surface.

Oil Country Tubular Goods (OCTG) is the general term given for pipes with connections at the end classified either as casing or tubing.

Drill PipeOilfield Drill Pipe and Oilfield Well

A drill pipe is made of hollow steel tubes to rotate the drill bit while drilling fluid is injected to aid the drilling process. Each end of a drill pipe is fitted with threaded tool joints used to provide high torque resistance and durability when subject to rotations. 

As drilling rigs come in different sizes, there are also different standardized drill pipes suitable for various drilling rig specifications.


Parts of a Drill Pipe

  • Pipe Body
  • Tool Joints: This can either be a box (female) or pin (male) end connection


OCTG Standards

API (American Petroleum Institute) and ISO (International Organization for Standardization) are the governing organizations for setting industry standards for oil and gas operations testing procedures.

Technical Specifications:

  • API Specification 5B: Threading, Gauging, and Inspection of Casing, Tubing, and Line Pipe Threads
  • API Specification 7-2: Threading and Gauging of Rotary Shouldered Connections
  • API Specification 5CT: Casing and Tubing
  • API Specification 5DP: Specification for Drill Pipe
  • ISO 11960: Petroleum and natural gas industries — Steel pipes for use as casing or tubing for wells

Pipe Body

Casing and Tubing Grades 

Pipe bodies are classified according to the following grades as indicated in API 5CT and the ISO 11960:

Casing and Tubing Grades

1 – Low strength

2 – Pipes suitable for environments with high H2S (hydrogen sulfide)

3 – High strength but lacks corrosion resistance

4 – Higher strength but also lacks corrosion resistance


Steel Grade Definition

Drill pipes are made with different chemical compositions and varying properties and dimensions. One way to classify drill pipes is through steel grade.

Steel grade is computed from required tensile strength and yield strength. Yield strength corresponds to the minimum pressure the drill pipe can take before deformation starts. Tensile strength refers to the maximum stress that the drill pipe can take when tension is applied before breaking. 

Types of Drill Pipe Steel Grades:

  1. E – lowest yield strength per unit area at 75,000 psi
  2. X – 95,000 psi
  3. G – 105,000 psi
  4. S –  highest yield strength at 150,000 psi used for deeper wells

The naming convention is the steel grade letter plus the minimum yield strength.

Grades X-95, G-105, and S-135 are considered high strength grades. They exhibit increased yield strength which is required for drilling deeper wells.

API grades (create visual chart here)

API Drill Pipe GradeMinimum Yield Strength (psi)

As the requirements for drilling have become more advanced over the years, manufacturers have created proprietary steel grades to support newer design requirements and harsher drilling conditions. Examples of drill pipes with proprietary steel grades are those used for critical service, sour service, thermal, or low temperature service.

Steel Grade Identification

Markings for the drill pipe grade identification can be found on the tool joint or base pin following the format below:

Manufacturer Symbol / Month Welded / Year Welded / Pipe Manufacturer / Drill Pipe Grade

Sample: AA 12 95 N E



Drill pipe lengths are classified according to the following ranges:

R1 – 18 to 22 ft

R2 – 27-31 ft

R3 – 38 to 45 ft

The length is computed based on the requirement. R3 pipes, while longer, have the disadvantage of increased wear as the load on each pipe will be greater compared to the shorter pipes.

Outer Diameter

The normal range for drill pipe outer diameter (OD) is from 2 3/8″ to 6 ⅝.

wdt_IDDP OD (in)Wgt (ppf)ID (in)DP Cpty (bbl/ft)Displacement (bbl/ft)Closed-End (bbl/ft)
12 ⅜4.851.9950.003870.00160.0055
52 ⅞8.352.3230.005240.00280.0080
93 ½11.202.9000.008170.00370.0119


Weld Type

Drill pipes come in different weld types. Deciding on the right weld type depends on the tube billet quality and structure requirements which are considered when designing a rig.


A seamless drill pipe is made when steel is pushed or pulled to forge a pipe over a mandrel, with visibly no seam produced in the product. Technically, it is seamless because there is no welding process when creating this pipe. Seamless pipes are preferred mainly for the uniform structure and high pressure tolerance.


An ERW drill pipe (Electronic Resistance Welded) is the result of cold-formed steel formed into a pipe. The pipe edges are are heated and joined by a high-frequency welder. Because of the manufacturing process, the surface of ERW pipes are easier to maintain and clean.



Submerged Arc Welding is performed by welding bended steel plates. SAW drill pipes are mainly used for pressure vessels because of its uniformity, compactness, and ductility.

Tool Joints 

The connections at the end of each pipe joins two pipes together to form a string. A connection can be classified as with high tension efficiency, which means that the tension load is higher than the pipe body. If the string breaks, only the pipe will break and not the connection.

If we say less tension efficiency compared to the pipe body, the connection will break if we apply maximum tension on the string.

Drill Pipe Specification with Upset and Tool Joint Chart

OD (in)Nom. Wt (lb/ft)UpsetGradeWall Thkns (in)ID (in)TJ Conn TypeTJ OD (in)TJ ID (in)TJ Pin Tong Space (in)TJ Box Tong Space (in)
wdt_IDOD (in)Nom. Wt (lb/ft)UpsetGradeWall Thkns (in)ID (in)TJ Conn TypeTJ OD (in)TJ ID (in)TJ Pin Tong Space (in)TJ Box Tong Space (in)

Oilfield Drill Pipe Thread

Parts of a Thread

  • Load flank: the surfaces that supports the string and comes into contact when it is tightly made up
  • Stabbing Flank: the surfaces that help guide the pin
  • Crest: high points of the thread
  • Root: low points of the thread


Different thread profile designs lead to different performance. For example, an ideal gap between stabbing flanks on the pin and box threads will lead to increase load resistance. 


Types of Threads

Connections are grouped into two types. 

  • API: Connections that are compliant to API standards stated in API Spec 5B. These connections are round threaded or buttress. Single shoulder connectors include the following: 
    • Regular
    • (IF) Internal Flush
    • (FH) Full Hole
    • (NC) Numeric Connection
  • Premium: Connections superior to the API standard requirements, usually made proprietary. Premium connections are manufactured in different sizes and can be made as threaded, coupled, or integral, where the pipe has double shoulders therefore providing more torque.

Sample of Performance Comparison

Drill Pipe Premium Tensile, Grades and Mechanical Specification Chart

OD (in)ConnectionGradeRangeWall (in)Nom. (lb/ft)AdjustedTJ OD (in)TJ ID (in)Tube_ID (in)TJ Yld (ft/lbs)Min Mut (ft-lb)Max Mut (ft-lbs)Prem Tensile (lbs)
wdt_IDOD (in)ConnectionGradeRangeWall (in)Nom. (lb/ft)AdjustedTJ OD (in)TJ ID (in)Tube_ID (in)TJ Yld (ft/lbs)Min Mut (ft-lb)Max Mut (ft-lbs)Prem Tensile (lbs)
12 3/8MW20G-105II0.286.656.812 1/21 3/81.8154,7002,7003,000150,662
22 7/8CTM26V-150II0.36210.411.723 1/21 1/22.15114,7008,4008,800333,070
32 7/82 7/8" HTPACG-105II0.36210.410.983 1/81 1/22.1518,5004,3005,100233,149
42 7/82 7/8" HTPACS-135II0.36210.411.083 1/81 1/22.1518,5004,3005,100299,763
52 7/82 7/8" AOHS-135II0.36210.411.293 7/82 5/322.1518,7004,3005,200299,763
62 7/82 3/8" HT-SL-H90S-135II0.36210.410.683 1/81.9752.1517,6003,8004,600299,763
72 7/8NC31S-135II0.36210.411.894 1/822.15113,2006,6007,900299,763
82 7/8XT27S-135II0.36210.411.243 3/81 27/322.15111,9005,9007,100299,763
92 7/8WT26S-135II0.36210.410.53 3/81 3/42.15111,2002,8009,800299,763
103 1/2HT38S-135II0.36813.315.544 7/82 9/162.76429,40014,70017,600381,870
113 1/2NC38S-135II0.36813.315.34 7/82 9/162.76420,10010,00012,100381,870
123 1/2XT-M34S-135II0.36813.314.364 1/42 9/162.76415,9008,0009,500381,870
133 1/2HT34-256 MPACS-135II0.36813.314.384 1/42 9/162.76418,1009,10010,900381,870
143 1/2NC38G-105II0.44915.517.284 3/42 9/162.60219,2009,60011,500350,867
153 1/2NC38S-135II0.44915.517.284 3/42 9/162.60219,2009,60011,500451,115
163 1/2NC38S-135II0.44915.517.54 7/82 9/162.60220,10010,00012,100451,115
173 1/2NC38S-135II0.44915.517.674 7/82 7/162.60222,00011,00013,200451,115
183 1/2NC38S-135II0.44915.518.1652 9/162.60220,10010,00012,100451,115
193 1/2TT380S-135II0.44915.517.664 13/162 1/22.60243,10021,60030,200451,115
204XT39CYX-105II0.331416.344 7/82 11/163.3435,30017,70021,200313,854
214XT39TSS-105II0.331416.344 7/82 11/163.3435,30017,70021,200313,854
224XT39XD-105II0.331416.484 7/82 11/163.3430,90015,40018,500313,854
234DS38S-135II0.331416.764 7/82 7/163.3432,10014,50019,300403,526
244DS38 12" WearKnotS-135II0.331419.334 7/82 7/163.3432,10014,50019,300403,526
254DS38 18" WearKnotS-135II0.331419.524 7/82 7/163.3432,10014,50019,300403,526
264XT-M38S-135II0.331416.224 3/42 11/163.3424,08912,00014,500403,526
274XT38S-135II0.331416.224 3/42 11/163.3427,60013,90016,600403,526
284XT39S-135II0.331416.344 7/82 11/163.3435,30017,70021,200403,526
294XT-M39S-135II0.331416.194 7/82 11/163.3431,50015,80018,900403,526
304TT390S-135II0.331416.74 7/82 11/163.3442,40021,20029,700403,526
314HT40S-135II0.331416.1352 11/163.3429,40014,70017,600403,526
324CTM39V-150II0.3815.718.652 11/163.2437,60025,43325,900507,701
334VX40VM-150II0.331416.645 1/42 3/43.3448,40027,60030,500448,363
344 1/2NC46S-135II0.33716.620.466 1/433.82639,00019,50023,400468,296
354 1/2NC46S-135III0.33716.619.596 1/42 3/43.82644,40022,20026,600468,296
364 1/2GPDS40S-135II0.33716.619.645 1/42 11/163.82635,50017,70021,300468,296
374 1/2Delta 425S-135II0.33716.618.945 1/433.82643,30034,80035,000468.296
384 1/2uXT40S-135II0.33716.619.475 1/42 13/163.82647,50023,80033,300468,296
394 1/2XT-M40S-135II0.33716.619.335 1/42 11/163.82643,70021,80026,200466,296
404 1/2CTM43Z-140II0.33716.618.695 1/43 1/43.82632,40016,20019,400485,641
414 1/2CTM43Z-140III0.33716.617.815 1/43 1/43.82636,40018,20021,900485,641
424 1/2TT485V-150II0.33716.620.0763 7/163.82675,40037,70052,800520,329
434 1/2XT-M40S-135II0.432023.115 1/42 11/163.6443,70021,80026,200581,247
444 1/2XT-M46S-135II0.432025.096 1/433.6475,20037,60045,100581,247
454 1/2TT-M485V-150II0.432023.1763 3/83.6471,90036,00043,100645,830
465NC50G-105II0.36219.524.116 5/83 1/44.27651,20025,60030,700436,149
475NC50S-135II0.36219.524.116 5/83 1/44.27651,20025,60030,700560,763
485GPDS50S-135II0.36219.525.896 5/83 1/44.27671,80036,10043,100560,763
495XT50S-135II0.36219.523.656 1/23 3/44.27676,90038,50046,100560,763
505XT50S-135II0.36219.524.526 1/23 1/24.27688,00044,00052,800560,763

Round threads feature v-shaped threads where the crest and roots have been rounded. The advantage of this thread is that it has good liquid sealability. However, this thread presents poor tensile resistance and can only support loads lesser than 80% of the pipe body resistance. 

Buttress threads look trapezoidal as the stabbing and load angles are designed with different values. Although this presents better tension resistance than a round thread, the liquid seability is poor.


Thread Characteristics


OD (in)Nom. Wt T&CE-75X-95G-105S-135
wdt_IDOD (in)Nom. Wt T&CE-75X-95G-105S-135
12 3/84.854760603066708570
32 7/86.858080102401132014550
53 1/29.5014150179201981025460

Connections are classified according to the following:

  • Thread profile: The shape of the thread and how the parts are designed
  • Metal seal: Determines the area of high pressure contact on the thread
  • Shoulder: Area inside the box where the tip of the pin is in full contact with
  • OD: outer diameter
  • Taper: rate of the change of diameter varying with length

Drill Pipe Specifications

Product Specification Levels

The advancements in OCTG led to a newer method of drill pipe classification called Product Specification Levels (PSL).

PSL 1 classifies OCTG that follows the API/ISO standards.

PSL 2 and PSL 3 cover the newer requirements that go beyond  the API/ISO standards. The pipes classified under PSL 2 and PSL3 differ in chemical composition, mechanical properties, manufacturing process, repair, and certification for traceability.

Oilfield Drill Pipe - PSL 1 and PSL 2 comparison


Drill Pipe Product Designation

In the oil and gas industry, a standard designation is followed to have a common understanding of the mass and dimensions of a drill pipe.

Sample Designation: 9 5/8″ 40# N80 BTC R3 


9 5/8″ specified the outside diameter in inches

40 is the weight in lbs/ft

N80 – steel grade

BTC R3- type of connection

When buying a new or used drill pipe, the product designation above allows the buyer to determine if the pipe matches the design requirements.

Specification Sheets

Drill Pipe specification sheets contain the following data:

  • Total Size and Weight
  • Grade
  • Range
  • Tool Joint
  • Pipe Body Capacity, Tensile Strength, Wall Thickness
  • Tubular Assembly Weight, Length (including the pins)
  • Connection Type

Used Pipe Classification

To validate if a drill pipe is suitable for further future use, the following classes have been defined by API.

  1. Class 1 – New and never been used drill pipes
  2. Premium – Reused pipe with the thickness of the remaining wall not less than 80% of the specification value
  3. Class 2 – Thickness of the remaining wall not less than 80% of the specification value
  4. Class 3 – Thickness of the remaining wall less than 70% of the specification value

Before a drill pipe can be reused, an inspector must check the current condition of the pipe/ This includes taking measurements of the wall thickness and recalculating the new maximum tension capacity. After the inspection, a used pipe can be deemed as qualified or not depending on the purpose.

Drill Pipe HS Codes 

When working with customs for importation or exportation of drill pipes, it will be useful to know the the HS (Harmonized System) codes used for drill pipes. The HS Code is a 6-digit identification used globally to classify products.

The first 2 digits classify the chapter, the next 2 are for the heading, and the last two for subheading.

Drill pipes fall under Chapter 73: Articles of Iron or Steel, Heading 04 for Tubes, Pipes And Hollow Profiles, Seamless, Of Iron (other Than Cast Iron) Or Steel.

The following subheadings are examples for line pipes:

10 – Iron

11 – Stainless Steel

21 – Drill Pipe

22 – Casing, tubing and drill pipe, of a kind used in drilling for oil or gas

A complete HS code sample would be 73041120 which corresponds to Stainless Steel blanks for tubes and pipes.

See this link for reference of HS codes.