Things to Note When Purchasing Oil Casing Pipe

Oil pipes are widely used to transport crude oil and natural gas to the surface after drilling, and they are also under the pressure of exploration. Oil casing is widely used to fasten the well wall or well wall of oil and gas wells to ensure the normal operation of the entire oil well after the drilling operation process and completion. It is an important guarantee for the normal operation of oil and gas wells after drilling and completion. Cement must be used to cement the casing after it is put into the well. It is different from oil pipes and drill pipes and cannot be reused. So, what should you pay attention to when purchasing oil casing pipe?

Based on the exploration and development deployment and drilling plan, users need to develop a demand plan in advance, including model, steel grade, buckle type, wall thickness, length range, weight, quantity and special requirements, such as specifications, grades, threads, etc. Grease type, thread protection type. Here are some things to consider when purchasing oil casing pipe.

(1) Clarify the pipe model, steel grade, thread type, wall thickness, length range, weight, quantity and special requirements.
(2) Clarify casing standards, such as API standards, national standards, industry standards, enterprise standards, etc. Relatively speaking, API standards are relatively loose, and each standard is slightly different. When filling in order conditions, the standards must be clear. Typically API pipelines are used.
(3) Check the supplier’s sales of similar products in the past three years. Is there a record of poor performance, quality and service conditions?
(4) Clarify pipeline quality inspection methods, implementation standards, inspection items, judgment standards and other matters.
(5) It is recommended that technical personnel from user units, testing institutions, purchasing departments and related departments participate. Drilling operation technicians can be invited to participate when necessary. Give full consideration to quality and choose manufacturers with reasonable prices.

(6) Purchase strictly in accordance with prescribed procedures and requirements.

Frequently Asked Questions about Oil Casing Procurement:

Q1: How to correctly select the casing steel grade and connection type based on well conditions?

A: This is the core of technical selection and must be based on the drilling design and geological data.

Steel Grade Selection:
Shallow Wells/Low-Pressure Formations: Economical steel grades such as J55, K55, and N80 can be used.
Medium-Deep Wells/General Pressure: N80 and L80 are the main steel grades, with L80 offering better sulfur resistance and overall performance.
Deep Wells/Ultra-Deep Wells, High-Pressure Gas Wells: High-strength steel grades such as P110, Q125, and V150 are required, and additional tests for crush resistance and internal pressure resistance are necessary.

Hydrogen sulfide (H₂S) acidic environment: Sulfur-resistant steel grades such as L80 (Type 1), C90, and T95 must be selected, and their hardness must meet NACE MR0175/ISO 15156 standards (typically ≤HRC22).

Connection type selection:
API threads (e.g., ST&C, LTC, BTC): Low cost, suitable for vertical wells, shallow wells, and well sections with low gas tightness requirements. This is the most basic choice.

Premium connections: High cost, but superior performance. Should be preferred in the following conditions:
1. Highly deviated wells and horizontal wells.
2. High-temperature, high-pressure wells and wells containing corrosive media.
3. Production casing and tailpipes requiring high gas tightness.
4. Conditions requiring the withstand of significant bending and alternating loads.

Q2: What key certificates and documents should be considered when purchasing API casing?

A: To ensure product compliance and quality traceability, the following documents must be requested and verified:

1. Proof of API certification from the manufacturer.

2. API 5CT Material Test Report (MTR), which should include:
Complete chemical composition analysis.
Full-size tensile test, hardness test, impact test, and other mechanical property data.
Hydrostatic pressure test and non-destructive testing results.
Corresponding furnace number, batch number, and pipe number.

3. Third-party inspection reports (e.g., SGS, BV, DNV, etc.): For critical wells or large-volume purchases, it is recommended to commission an independent third party to conduct a pre-shipment inspection (PSI).
4. Certificate of origin and quality assurance certificate.

Q3: What are some easily overlooked key clauses in casing purchase contracts?

A: In addition to price, quantity, and delivery date, please be sure to clarify:

Technical standards and deviations: Clearly specify which version of API 5CT is being implemented, and any additional technical agreements (such as stricter dimensional tolerances, special NDT requirements). Acceptance and Rejection Clauses: Clearly define the buyer's rights, location, method, and time limit for re-inspection, as well as the handling procedure for non-conforming products (return, exchange, discount).
Packaging and Labeling: Clearly define the packaging method (bundled, boxed), corrosion protection requirements, and the markings on each pipe (must include steel grade, dimensions, production batch number, etc.).
Price Adjustment Mechanism: For long-term contracts, the floating formula and adjustment cycle for alloy surcharges (Moly Surcharge, etc.) must be agreed upon.
Intellectual Property and Liability: If special threads are involved, patent authorization and liability boundaries must be clearly defined.

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