A Comprehensive Guide to Drill Pipe Procurement: From Selection to Acceptance

Procuring drill pipe is one of the most critical decisions in oil and gas drilling operations. Drill pipe not only forms the backbone of the drill string but also serves as the “lifeline” connecting surface equipment to the downhole drill bit—transmitting torque, circulating drilling fluid, and supporting the weight of the drill string. Selecting the wrong steel grade can lead to premature failure; choosing the wrong thread type may result in connection leaks or even thread stripping; and neglecting proper verification of quality documentation could allow defective products to enter the wellbore, with potentially catastrophic consequences.

This article will systematically walk you through the entire drill‑pipe procurement process, covering five key dimensions: understanding industry standards, conducting needs assessments, identifying selection criteria, evaluating and shortlisting suppliers, and performing quality acceptance inspections.

I. Understanding the API 5DP Standard: The “Constitution” of Drill Pipe Procurement 

The starting point for drill pipe procurement is understanding API Spec 5DP—this international technical standard for drill pipe, published by the American Petroleum Institute, serves as the fundamental basis for drill pipe procurement across the global oil and gas industry.

Core content covered by API 5DP

API 5DP specifies the manufacturing requirements, test procedures, material grades, and dimensional tolerances for drill pipe. It defines three core dimensions:

1. Steel Grades

API 5DP defines four primary steel grades—E75, X95, G105, and S135. The number in the grade designation indicates the minimum yield strength, in thousands of psi:

S135 is the highest-strength standard steel grade, suitable for deep wells and high‑stress environments; E75 offers superior ductility and enhanced corrosion resistance, making it ideal for shallow wells and cost‑sensitive projects. In addition, API 5DP defines the SS series of sulfur‑resistant grades (SS95/SS105/SS135) as well as the V150 ultra‑high‑strength grade.

2. Product Specification Level (PSL)

API 5DP classifies drill pipes into three grades—PSL1, PSL2, and PSL3:

Higher PSL grades are typically used in deep wells, offshore drilling, and high-risk environments. When placing an order, the PSL grade should be clearly specified.

3. Dimensions and Length

API 5DP defines nine standard outside diameters: 2 3/8″, 2 7/8″, 3 1/2″, 4″, 4 1/2″, 5″, 5 1/2″, 5 7/8″, and 6 5/8″. There are three standard length ranges: R1 (1,822 ft), R2 (2,731 ft), and R3 (3,845 ft), with R2 being the most commonly used.

Procurement Highlights: During the RFQ process, explicitly require suppliers to provide API Monogram certification and an MTC report compliant with API 5DP. API certification ensures that drill pipe undergoes comprehensive quality control throughout the entire manufacturing process, from raw materials to the finished product.

II. Assessing Drilling Needs: Five Questions to Answer Before Selecting Equipment 

Before reviewing any product specifications, first answer the following question:

1. How deep is the well?

< 4,000 meters → E75 is sufficient

4,000–5,500 meters → X95

5,500–7,000 meters → G105

> 7,000 meters → S135

2. What is a well type?

Vertical well → Standard drill pipe is sufficient; the heavy-weight drill pipe provides the primary drilling weight.

Directional wells/horizontal wells → Require high-torque-resistant drill pipes; heavy-weight drill pipes (HWDP) may be necessary.

Extended-reach well (ERD) → S135 steel grade + double‑tapered shoulder joint (DSTJ)

3. What are the stratigraphic conditions?

Hard formations/abrasive formations → Require hardbanding

In H₂S-containing environments, SS sulfur‑resistant steel grades must be selected.

High-temperature, high-pressure (HPHT) → Requires a higher PSL rating.

4. How high is the torque requirement?

Standard torque → Sufficient connection for the NC series

High torque → Consider Double-Tapered Shoulder Joint (DSTJ) , can provide 20–50% higher torsional strength

5. What is a budget constraint?

Select the most cost-effective solution while meeting technical requirements, and avoid “overspecification.”

III. Drill pipe Selection: An In-Depth Explanation of the Five Key Parameters 

1. Outer Diameter (OD) — Determines Torque Capacity and Fluid Efficiency

In onshore drilling, 5″ and 5½″ are the most commonly used sizes, offering an optimal balance among strength, flow capacity, and compatibility with BHA components.

2. Steel grade—determines the ultimate strength

When selecting a steel grade, keep in mind that a higher grade is not always the better choice. E75 offers superior ductility and greater resistance to cracking in corrosive environments; S135 provides the highest strength but at a higher cost, and it requires a specialized sulfur‑resistant grade for H₂S‑contaminated conditions.

Quick Selection Guide:

Asai (<4,000 m) → E75

Standard oil and gas well → G105

Deep well/complex well → S135

3. Thickened type—determines connection strength

IU (Inner Thickened): The inner diameter at the pipe end is reduced, while the outer diameter remains unchanged.

EU (Extra Thick): The outer diameter at the pipe end is increased, while the inner diameter remains unchanged.

IEU (Inner and Outer Thickened): Both inner and outer diameters are altered simultaneously.

The thickening type determines the strength of the joint—insufficient thickening may render the connection a weak point in the drill string.

4. Connection Threads — Determining Drill String Integrity

The API defines multiple thread types:

NC Series: API‑recommended first choice, with superior fatigue resistance.

REG (Regular Type): Highest strength, used for connecting BHA and drill bits.

IF (Internal Flat Type): Has been phased out and replaced by NC.

FH (through‑eye type): 51/2″ FH is still in use.

Procurement Recommendation: In new projects, prioritize the use of NC-series threads.

5. Length range — determines operational efficiency

R2 (2731 ft): The most widely used, offering the optimal balance between operational efficiency and handling convenience.

R3 (3,845 ft): Deepwater drilling and deep wells with fewer connections.

R1 (1822 ft): Special Application

IV. Supplier Screening: How to Assess Manufacturer Qualifications? 

Hard requirements (must be met)

1. API 5DP Certification: Suppliers must hold a valid API Monogram License.

2. Complete MTC report: Each batch of goods is accompanied by a factory inspection certificate conforming to EN 10204 3.1.

3. Traceability System: Each drill pipe’s heat number is uniquely matched to its MTC.

Bonus Points (Recommended for Assessment)

1. Third-party inspection support: Does it support independent third-party inspections such as SGS, BV, TÜV, etc.?

2. International Certification: Whether the product holds regional certifications such as GOST (Russia), NS1 (Europe), etc.

3. Industry Experience: Do you have a track record of successfully fulfilling at least three similar orders?

4. Delivery Records: Is there a history of on-time deliveries to your work area?

Supplier Evaluation Checklist

V. Quality Acceptance: The Final Line of Defense Before Entry into the Mine 

Document Acceptance (Mandatory Item)

1. MTC (Factory Test Certificate):

Does the furnace number match the physical drill pipe?

Are the chemical compositions within the API 5DP standard limits?

Do the mechanical properties (yield strength, tensile strength, and elongation) meet the specified requirements?

Is it EN 10204 3.1 or a higher grade?

2. Nondestructive Testing Report:

Ultrasonic Testing (UT) Results

Magnetic Particle Testing (MT) Results

Check whether the entire length of the pipe is covered.

3. Dimensional Inspection Report:

Do the outer diameter, wall thickness, and length meet the order requirements?

On-site acceptance (pre-entry inspection)

1. Visual inspection: Check the pipe body for dents, crush marks, scratches, or corrosion.

2. Caliper Inspection: Verify that the caliper gauge can pass freely through the entire drill pipe.

3. Thread Inspection: Check for thread wear, galling, or damage.

4. Identification Verification: Verify that the steel grade and heat number match those on the MTC.

5. Dimensional Measurement: Verify that the outer diameter and wall thickness are within the specified tolerances.

The Value of Third-Party Inspection

For critical projects, it is recommended to engage an independent third-party inspection agency (such as SGS, BV, or TÜV) to conduct on-site inspections or pre-shipment inspections. Third-party inspections can provide:

Independent quality verification

EN 10204 Grade 3.2 MTC (Third-Party Verified)

Reduce procurement risk

VI. Frequently Asked Questions (FAQ) on Procurement 

Q1: How should you choose between new and used drill rods?

New drill pipes are more expensive but offer predictable performance and complete documentation; older drill pipes are lower in cost but require careful assessment of remaining wall thickness and fatigue history. For critical projects, it is recommended to use new drill pipes.

Q2: How can you verify whether a supplier’s API certification is valid?

Suppliers are required to provide their API logo license number, which will be verified through the official API certification inquiry system.

Q3: What is the difference between an MTC and a “Certificate of Conformity”?

The MTC includes detailed chemical composition analysis and mechanical property data; the certificate of conformity is merely a declaration and does not provide any data. An MTC must be requested at the time of procurement.

Q4: Why is third-party inspection necessary?

Third-party inspection provides independent quality verification and carries legal weight in the event of disputes. For export projects and international tenders, third-party inspection is standard practice.

Q5: What hidden costs should be considered when purchasing drill rods?

In addition to the unit purchase price, the following factors must also be taken into account: transportation and insurance, customs clearance and duties, warehousing and maintenance, inspection costs, and losses incurred from production downtime due to non‑conforming quality.

VII. Summary: A Ten-Step Checklist for Drill Pipe Procurement

Drill pipe procurement is not a simple “purchase”; it is a systematic process that spans from understanding specifications to matching requirements, and from supplier selection to quality inspection. Only by rigorously implementing each step of this process can we ensure the acquisition of drill pipe products that are safe, reliable, and cost‑effective.

Do you need to procure API 5DP‑certified drill pipe for your project?

Hebei Longway Petroleum Equipment Co., Ltd.

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