Drill pipe with thickened end is a key consumable in oil and gas drilling. It affects the efficiency, safety and economy of well drilling. This article deeply analyzes the three types of thickened ends of IU/EU/IEU in oil and gas drilling.
Preface
According to the Global Market Insights report, the global drill pipe market will reach $6.7 billion in 2023, of which thickened drill pipe accounts for 58% of the market share. According to statistics from the American Petroleum Institute (API), about 29% of downhole accidents are related to drill pipe breakage, with the highest damage reaching $2.3 million, which fully proves how important the strength of drill pipe is. When facing pressures above 10,000 psi, the stress concentration factor at the threaded connection of traditional drill pipe can reach 3.8-4.2, while the stress concentration of thickened drill pipe can be reduced to 2.1-2.5.
Core knowledge system of drill pipe with thickened end
Technical Definition
Thickened end drill pipe is a reinforced drill tool that increases the thickness of both ends of the drill pipe through hot forging, thereby enhancing the compressive resistance. The slope of its transition zone is strictly limited to ≤1:4, which meets the requirements of API SPEC 5DP Section 6.3.2. This design has been significantly improved in fatigue resistance, with an improvement of up to 300% to 450%.
Comparison of technical parameters of three types of thickening
type | Thickening position | Applicable well depth | Improved torsional strength | Cost Index |
Internal Thickening (IU) | Thickening of inner wall | 4,500-7,500m | 35%-40% | 1.2x |
External thickening (EU) | Thickening of outer wall | <3,000m | 25%-30% | 1.0x |
Internal and external upholstery (IEU) | Synchronous thickening inside and outside | >8,000m | 55%-60% | 1.8x |
In-depth analysis of application scenarios:
Shale gas horizontal well: Shale gas horizontal well is complicated and has serious wear on drill pipe, so EU type drill pipe should be used, because the outer layer of this drill pipe has been specially treated with wear resistance, and has a wear-resistant layer that can withstand more than 200 times of casing wear. Thereby improving the efficiency and safety of the overall operation, providing a strong guarantee for the efficient exploitation of shale gas.
Deepwater drilling: For deepwater drilling operations, IEU type drill pipe is the most suitable, because this drill pipe can withstand high pressure and can maintain safe sealing under an external pressure of 2,000psi. Since the deeper the water, the greater the water pressure, this feature is very important for deepwater drilling operations.
High sulfur oil field: For the exploitation of high sulfur oil fields, U-type drill pipe should be used and LC-95 material should be used. This strong combination can show extremely high corrosion resistance, and the sulfur stress corrosion index reaches the NACE MR0175 standard.
API Standard Manufacturing Process
Six-step hot forming process
Heating the pipe end: The pipe end is heated by a medium-frequency induction coil of 3,000-10,000Hz, which can quickly heat the temperature of the pipe end to 1,200±50℃ within 3 seconds.
Hydraulic forging: A 500-2,000-ton high-pressure hydraulic press is used for radial extrusion, and the wall thickness increase rate is strictly controlled between 18%-22%.
Transition zone forming: The pipe is processed using a mold to form a 1:4.5-1:5 gradient that meets the strict requirements of the API standard for the transition zone to ensure its performance.
Heat treatment: The normalizing and tempering processes are used. .Keep the hardness in the range of HRC22-26. Nondestructive testing:
Ultrasonic flaw detection (UT): detect the area where the wall thickness deviation is greater than ±5%
Magnetic particle inspection (MPI): identify surface micro cracks (sensitivity level 2)
Thread processing: use VAM TOP and other advanced buckle types, and control the close distance within ±0.05mm
FAQs：
1. How to measure the length of the thickened end?
According to API RP 7G Appendix B: clean the oil stains on the pipe end, use a special caliper to measure the distance from the starting point of the thickened section to the pipe end, and take the average value at four symmetrical positions, with a tolerance of ±3mm.
2. Can the thickened drill pipe be repaired and used?
Limited to local wear outside the transition zone, and must meet the following requirements: repair times ≤ 2 times, pass 125% working pressure test after repair, and cannot be used in well conditions with H₂S content > 5%.
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