Characteristics of Non-dig Drill Pipe

DHDT水平定向钻杆的主要生产工艺为整体加厚式 其设计和制造工艺具有以下特点
One-piece, upset-forged type as main production process of DHDT HDD drilling pipe
Characters for design and manufacture process as below.
HDD drilling pipe patented design and patented manufacture process

DHDT carefully selected seamless steel tube
To guarantee premium quality product, all products material is sourced from Shanghai Baosteel specially developed hot rolling high strength alloy structure tube for oil and gas drilling tools without considering about high cost. This material uses external refining and vacuum degassing technology with even composition and high purity. The lowest content of harmful chemical elements such as phosphor and sulfur is reached. Non destructive test is performed according to NDT standard Level 2 with combination of eddy and ultrasonic to guarantee material quality without any defect.

DHDT scientifically designed upset end
加厚端内外截面变化的横截面不重合,避免单个横截面上应力过度集中(Stress Concentration),尤其是内锥面(Internal Upset Taper)消失处(Runout)和外锥面(External Upset Taper)消失处(Runout)不重合;
Internal and external variational cross sections on upset end are not on the same cross section, especially runout of internal upset taper and runout of external upset taper is not on the same cross section.

DHDT加厚工艺(Upsetting Process)精计算
Precise calculation of upsetting process by DHDT
精准计算---Super Forge软件工艺模拟(Processing Simulation)---加厚试验---小批考核---批量考核
Conclusion for DHDT upsetting process confirmed by below steps
Precise calculation – Super Forged software processing simulation -- upsetting test – small quantity check – batch check

DHDT production process guaranteed by precise manufacture equipment
It is easier to draw and calculate than actually upsetting the upset end satisfying design requirement. The temperature precision of induction heater from DHDT is controlled in ±30℃. Heating length precision is controlled in ±10mm. Location precise of pipe material in die is ±5mm. Pipe material length shortening amount precise is ±3mm. Proved by decade years of practice, advanced upsetting equipment from DHDT can fully satisfy upsetting technology and design requirement. DHDT can make promise that each drilling pipe from DHDT is qualified and accepting inspection by customer random selected sample.

多点测温步进式热处理炉 保证强度和韧性最佳配合
Continuous belt furnace for heat treatment with multi-point temperature measurement
Guarantee perfect match between strength and toughness
中国无锡DHDT是目前中国国内唯一在水平定向穿越钻杆领域中采用天然气步进炉进行热处理(continuous belt furnace for heat treatment)的公司。淬火(hardening)、高温回火热(high temperature tempering)处理方式采用封闭式加热(heating in enclosure space),炉内多点采用热电偶(Thermocouple)控温,淬火炉保温区(holding section)炉温均匀性(furnace temperature uniformity)为20℃,高温回火炉保温区炉温均匀性为10℃。精准确定的专利淬火工艺,在保证管体及加厚端充分奥氏体化(austenitizing)的同时,又不会引起奥氏体晶粒粗大(coarsening of austenite grain size)。钻杆淬火出炉后,迅速采用内喷外淋的冷却方式对其进行均匀冷却,冷却速度大于钻杆材料的临界冷却速度(critical cooling rate),且不会产生淬火裂纹(quenching crack),确保马氏体转化率(percent conversion of martensite ),尤其是钻杆加厚区的马氏体转化率。回火装备和专利回火工艺保证钻杆强度和韧性的最佳配合。

DHDT in Wuxi city of China is the only company in domestic who adopts natural gas continuous belt furnace for heat treatment in HDD drilling pipe field. The heating of hardening and high temperature is conducted in enclosure space. Temperature in furnace is controlled by multi-point thermocouple. Furnace temperature uniformity of quenching holding section is 20℃. Furnace temperature uniformity of high temperature tempering area is 10℃. Patented quenching process with accuracy can guarantee pipe body and upsetting area fully austenitizing simultaneously but not bring coarsening of austenite grain size. After drill pipes finish quenching and come out from furnace, immediately even cooling them by inner spray and outer shower. Cooling speed is faster than critical cooling rate of drill pipe material. Quenching crack will not appear and make sure percent conversion of martiensite especially in the drill pipe upsetting area. Tempering equipment and patented tempering process guarantee the best relationship between drill pipe strength and toughness.

双马DHDT企业标准机械性能和API SPEC 5DP标准机械性能对比表
Comparison table of mechanical property between DHDT company standard and API SPEC 5DP standard

DHDT enterprise standard requirements are higher than API standard. Drill pipe parameters like tensile strength, torsion strength, compressive strength, bend radius improved a lot with high toughness at same time.
DHDT actually mechanical property testing level for samples

DHDT V-型口吸收冲击功实物检测水平
DHDT Actual Samples Test Results for V-type Gap Absorbing Impact Energy

Double shoulder design for pin and box connection
双台肩结构提高扭矩的原理 Principle of double shoulder structure torque improvement
- 在内外螺纹接头小端增加一个副台肩
- 主台肩提供密封和承受较大扭矩
- 副台肩承受部分扭矩,过载保护
- 副台肩可起到一个辅助密封作用,增强整个钻杆的密封能力
- Add a secondary shoulder on the pin and box thread connection end
- Main shoulder with function of sealing and bearing more torque
- Secondary shoulder with function of partial torque and overload protection
- Secondary shoulder has function of complementary sealing. The whole drill pipe sealing ability is improved.

双台肩接头对力学性能改善 Load bearing capacity improved by double shoulder connection
Stress distribution diagram on normal single shoulder connection
Stress distribution diagram on double shoulder connection
Stress distribution diagram on DHDT new double shoulder connection when double shoulder contacts
The stress on each thread in more even.
Stress distribution diagram when main shoulder of DHDT new locking connection contacts, auxiliary shoulder doesn’t contact
Stress distribution of each thread is not even. The stress on the threads near main shoulder is big.

DHDT特殊扣钻杆的研发 Research and development of DHDT drill pipe with special thread
High torsion resistance and super high torsion resistance thread connection by DHDT is in stage of developing and testing, it will serve for customers in near future. Main special thread connection under development at present is tri-lobular thread type, trapezoidal thread type, buttress thread type and oblique triangular thread type with low stress. DHDT double shoulder thread connection already gained several patents.

管体和螺纹喷丸处理 提高产品疲劳使用寿命
Shot peening treatment for pipe body and thread Improve product anti-fatigue service life
Each of DHDT drill pipe is treated by shot peening. After shot peening treatment, surface of drill pipe and thread gets residual pressure stress. This stress can improve drill pipe anti-fatigue service life. Shot peening treatment on thread can help thread compound adhering to thread. Thread service life is improved.

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