The latest drilling tool reconstruction and repair technology: laser cladding repair and reconstruction technology + metal magnetic memory detection technology

Abstract: Petroleum drilling tools occupy a considerable cost in petroleum drilling engineering. The working environment of drilling tools in the underground is very harsh, not only subjected to composite alternating stresses such as tension, pressure, and torsion, but also subjected to erosion and corrosion of drilling fluid. After using drilling tools for a period of time, they will produce surface wear, internal cracks, etc., resulting in the scrapping of drilling tools. Therefore, rebuilding and repairing damaged drilling tools and putting them back into use have significant economic and social benefits. This article introduces the remanufacturing and repair technology of drilling tools, including identification of drilling tool damage, classification of levels, reconstruction and repair, and inspection and evaluation.

1. Damage situation and corresponding treatment of drilling tools

The reconstruction and repair technology of drilling tools is aimed at different parts and damage results of drilling tools. Fuzzy support vector machine theory is used to identify drilling tool damage and classify damage levels. Based on the classification results, drilling tools with macroscopic and microscopic damage are reconstructed and repaired, including drilling tool body repair and drilling tool joint repair. Finally, magnetic memory technology is used to detect the reconstructed drilling tools, and they can be re-entered into the well after meeting the requirements.

2. Repair of drilling tool body

The friction between the drilling tool body and the wellbore wall during use can cause wear, thinning, and even puncture. The failure of the drilling tool body generally occurs 500mm below the joint, and only a few occur on the wear-resistant belt of the internal threaded joint in the thickened transition zone at the connection between the joint and the body.

Laser cladding repair and reconstruction technology is a surface coating that rapidly heats and melts hard alloy powder or other wear-resistant materials under the action of a laser beam, forming a metallurgical bond with the drilling tool body, thereby improving the wear resistance, corrosion resistance, heat resistance, and oxidation resistance of the drilling tool body. It has the characteristics of high welding accuracy, wide applicability, regular welding surface size, and low stress concentration. It can be used for repairing complex situations such as irregular shape of drilling tool damage, internal depth defects, and uneven pipe wall thickness. It is a highly automated reconstruction and repair technology. Therefore, appropriate repair techniques should be selected based on the different types and degrees of damage to drilling tools to meet the technical and economic requirements of drilling tool repair.

3. Repair of drilling tool joints

Most failed drilling tools are caused by damage to the joint of the drilling tool. The types of joint damage are generally joint deformation, joint end face puncture, thread damage, and stress concentration fracture at the root of the thread. For the above types of drilling tool joint damage, there are several methods for reconstruction and repair:

(1) Manual welding repair: Using tungsten carbide welding rods, a gas shielded arc is generated under the heat of the arc. At the same time, the melted tungsten carbide is covered on the worn surface of the joint, forming a 10mm wide and certain thickness wear-resistant band at the worn part of the joint. The advantage is that it can directly treat the damaged parts of the drilling tool on site.

(2) Armor welding: using special welding pliers, 1000A DC arc welding machine, and cast tungsten carbide welded on the surface of the joint with water glass attached. The advantage is that on-site operation is simple and convenient, but the disadvantage is that it is difficult to operate in low temperature, wind and rain weather conditions, and the arc temperature is high. Careful operation is required to avoid damaging the joint.

(3) Oxygen acetylene overlay welding: Oxygen acetylene flame overlay welding is a multi-purpose overlay welding heat source. During overlay welding, the melting depth is shallow, the melting amount of the drilling tool body is small, the obtained overlay welding layer is thin, the surface is smooth, and the flame temperature is low. After overlay welding, the original properties of the hard alloy in the composite material can be maintained. The advantage is that the flame temperature is low and adjustable, and the repaired tungsten carbide does not melt to maintain wear resistance, with low cost. The disadvantage is high labor intensity and low melting efficiency.

(4) Plasma spray welding: Using a DC arc welding machine with steep drop characteristics as the power source, a high-frequency spark is used to ignite a non transfer type plasma arc between the tungsten electrode of the spray welding gun and the nozzle. The non transfer arc flame is used to ignite the transfer type plasma arc between the tungsten electrode and the drilling tool joint. The alloy powder is continuously supplied by the powder feeder according to the required amount, and is blown into the spray welding gun by the powder feeding airflow, sprayed onto the drilling tool joint, and an alloy cladding layer is obtained on the joint. This process has high surface hardness, firm welding, and good toughness.

(5) Plasma arc welding: Welding is achieved by using a compressed arc between electrodes and joints. The electrodes used are usually tungsten electrodes. Plasma arc welding has a high energy density, strong penetration ability, and can weld wear-resistant hard alloys to the surface of drilling tool joints. The advantages are good wear resistance, high welding strength, and the ability to perform large-scale processing. The disadvantages are high cost of hard alloy materials, difficult on-site operation of required equipment, and certain temperature requirements for equipment.

(6) CNC cutting machining: When using cutting machining to repair the threads of drilling tools, due to the general length of drilling tools being around 9m, installation and alignment are inconvenient, manual cutting and accuracy control are not easy. Therefore, in the repair of drilling tool threads, a CNC lathe is used and a photoelectric decoder is installed on the lathe spindle to ensure that it can cut along the original thread groove.

4. Magnetic Memory Testing of Drilling Tools

Metal magnetic memory testing technology is a fast non-destructive testing method that uses the metal magnetic memory effect to detect stress concentration areas in components. It can diagnose the stress concentration areas inside ferromagnetic metal components, such as micro defects and early failure, damage, etc. It is a new testing method in the field of non-destructive testing.

When ferromagnetic components in the geomagnetic field environment are subjected to external loads, magnetic poles are generated in the stress concentration area, forming a demagnetization field, which minimizes the permeability of the ferromagnetic metal and forms a leakage magnetic field on the metal surface. The circumferential component of the leakage magnetic field strength has the maximum value, while the axial component changes sign and has a zero value. This irreversible change in magnetic state can still remember the location of stress concentration even after the working load is eliminated. A detection instrument based on the basic principle of metal magnetic memory effect can evaluate the degree of stress concentration and the presence of microscopic defects in drilling tool joints by recording the distribution of magnetic field intensity components perpendicular to the surface of the joint in a certain direction.

By using the metal magnetic memory method to detect the repaired drilling tool body and joints, the magnetic field strength curve and gradient curve are obtained, and they are analyzed with the magnetic memory signals before and after repair, calibration drilling tools, and repair. The stress concentration changes of the reconstructed and repaired drilling tools are compared. Some magnetic memory detection indicators even exceed the detection indicators of the calibration drilling tools, which can accurately determine whether the repaired drilling tool body and joints meet on-site requirements. Therefore, magnetic memory detection technology can be used for the quality appraisal of finished drilling tools with good results.

5. Conclusion

(1) The technology of drilling tool reconstruction and repair utilizes damage identification, classification, reconstruction and repair, as well as magnetic memory detection technology to safely reuse drilling tools, improve their utilization rate, and reduce drilling costs;

(2) By using fuzzy support vector machine to classify the feature values of the detection samples, the state to which they belong can be obtained. When identifying and classifying the damage degree of drilling tools, it is then determined whether they need to be remanufactured based on their state;

(3) Based on the actual damage location and degree of drilling tools, combined with the actual situation of drilling tool damage, an economical and efficient drilling tool remanufacturing process is selected;

(4) By using metal magnetic memory detection technology to analyze the magnetic memory signal of the repaired drilling tool and detect the magnetic field distribution on the surface of the material, it can be found whether the reconstructed and repaired drilling tool meets the requirements for re entering the well.

(END)

This article is excerpted from the Chinese version of Li Tianren's Latest Drilling Tool Reconstruction and Repair Technology

Company product profile:
Luoyang Golden Egret Geotools Co.,Ltd. founded in2012,is wholly-owned by iisted company XiamenTungsten Co.,Ltd (XTC).As a backbone cemented carbideenterprise of XTC with registered capital of 1.05billionRMB and first investment of ibillion RMB,GEOTOOLSspecializes in producing and selling high quality tungstenpowder,Tungsten Carbide Powder, carbide anvils,carbideroll rings,carbidesubstrates for PDC bit,mining drill bitsand hard facing materials.
Based on decades of production experience of WC based hard-facing materials, world-class technologies and modernautomatic production lines, GEOTOOLS dedicates into development and production of high quality hard facing materialwith high hardness, best wear resistance, best corrosion resistance and application solutions.
XTC brand Thermal Spray Powder mainly includes Wc- based & Cr3C2-based. The WC coating has high hardnessdurable wear resistance, abrasion resistance, corrosion resistance and high bonding strength, mainly used in oil &gas valves, mining tools, injection screws and printing machinery parts, The Cr3c2 coating has higher thermalstability and anti-oxidation, which can be used in a high temperature and corrosive environment, e.g. inner- wall ogas pipeline and pump.
With high degree of sphericity & excellent alloy organization, cemented carbide pellet is mainly used in weldingas an additive material of PTA Powder and tubular weldina rod to improve the wear resistance of the work pieces.
GEOTOOLS provides mono-crvstalline WC-based, coarse-arain wC-based, casting WC-based and other kinds ofPTA powder. With the high quality material, most advanced production lines and word-class technologies, the PTAcoating has high hardness, durable wear resistance, high welding velocity, and low porosity characteristics. Mainlyused in Mining, Oil driling, agriculture machinery, and machining for welding and repairing.
The hard phase of GEOTOOLS tube rods is tunasten or its products with high wear resistance. Tubular welding rods aresuitable for flame brazing and widely used for surface strengthen for oil and mining drill bits.