Drill pipe is widely used in hydrological exploration, geological drilling, oil and gas exploration, and other fields. As an important part of the entire drill string, the drill pipe plays a pivotal role in the drilling process. The quality of the drill pipe and the quality of maintenance and maintenance have an important impact on the on-site use effect, the occurrence of drilling tool accidents, and the construction cost. Below, the author only talks about his superficial understanding of the use of friction-welded drill pipes and the maintenance and management on the construction site.



At present, the commonly used drill pipe bodies in the domestic oil and gas industry mainly include four steel grades: E75, X95, G105, and S135, the material of the drill pipe joints is mostly SAE4137H, and the outer diameter of the drill pipe is 2 3/8″～6 5 /8″, with various sizes. The higher the steel grade of the drill pipe, the higher the strength and the stronger the bearing capacity. But it should be noted that when choosing drill pipes, the higher the strength, the better. Because in the drilling fluid medium, as the steel grade increases, the corrosion fatigue strength of the drill pipe will decrease, that is, in a corrosive environment, the high steel grade drill pipe is more sensitive to the corrosive medium, and the corrosion fatigue strength will also decrease. The more, the more prone to corrosion fatigue fracture accidents. It is suggested that users should select the most suitable drilling tools for drilling operations according to the principle of "select low-grade drill pipes as much as possible on the premise of meeting the strength requirements", which not only reduces the procurement cost but also reduces the cost of drilling. probability of an accident.

Drill pipe use

1. Overall structure of friction welded drill pipe

The friction welding drill pipe is connected into a whole by the internal and external thread joints and the pipe body of the drill pipe by friction welding. The drill pipe rotates under the drive of the turntable or the power head, transmits the power to the drill bit at the bottom of the hole, and delivers the drilling fluid to the cutting surface of the drill bit. The drill pipe occupies a very important position in the entire drilling construction.



At present, there are two main standards for friction-welded drill pipes produced by most domestic drill pipe manufacturers: the People's Republic of China oil and gas industry standard SY/T 5114-2014 and the internationally recognized API 5DP implemented by the American Petroleum Institute Drill pipe specification. These two standards have made clear requirements for the parameters and performance indicators of the drill pipe body, joints, friction welding area, and other parts. Users can use this as the main reference for drill pipe selection and quality evaluation.



2. Use and management of drilling tools on construction site

Precautions before the drill pipe go down the well:

Before the drill pipe is used in the well, the internally threaded joints should be neatly placed in the direction of the drill floor according to the specifications and placed on the movable drill pipe frame with sufficient piers above 0.3m from the ground to prevent water, moisture, soil, etc. Corrosion on the drill pipe; the drill pipe frame should be kept parallel and on the same level to prevent the drill pipe from being bent and deformed; the drill pipe at both ends of the pipe frame should be clamped with plugs to prevent the drill pipe from rolling and falling.



Before the drill pipe is placed on the drilling floor, the thread of the drill pipe joint and the sealing surface of the shoulder should be thoroughly cleaned and inspected, and the drilling can be used only after confirming that they are in good condition. When the drill pipe goes up and down the drill floor, the drill pipe joint must wear a protective wire (steel protective wire is recommended) to prevent the joint thread and shoulder surface from being bumped and damaged during the pulling process.



During the hoisting process of the drill pipe on the drill floor along the slideway, the winch should maintain a constant speed as much as possible. When the drill pipe leaves the slideway, it should be manually blocked with soft ropes to prevent bumping.



Before the single connection operation at the wellhead, the joint thread and shoulder sealing surface should be cleaned and inspected again. After confirming that there is no problem, the oil containing 60% fine metal lead powder or 40-60% fine metal zinc powder should be added. The special thread oil for drilling tools should be applied to the joint thread and the sealing shoulder surface in a sufficient amount and evenly (the thread and shoulder surface of the orifice female joint should also be fully and evenly applied with the special thread oil), and at the same time, dust should be prevented. and other foreign objects mixed into the threaded oil, affecting the performance of the threaded oil or scratching the thread and shoulder sealing surface.



Precautions in the use of drill pipe:

When the new drill pipe is used for the first time, it is recommended to unscrew the joint twice at the wellhead with a torque slightly lower than the specified value. After confirming that the joint thread and sealing surface is in good condition, apply sufficient thread oil evenly and follow the regulations. The torque tightens the joint threads for subsequent use in the well. The operation of this running-in buckle is beneficial to strengthening the surface hardness of the thread, enhancing the anti-galling performance of the thread, and prolonging the service life of the drill pipe.



When the wellhead is connected to the drill pipe, it is necessary to manually straighten and guide the buckle to prevent the male joint from impacting the end face or thread of the female joint and causing damage; then use the chain pliers to manually identify the buckle, introduce no less than two buckles, and then use the hydraulic power pliers according to the regulations. Tighten the thread of the drill pipe joint with torque (different steel grades, specifications, and water hole sizes require different make-up torques, which must be treated carefully).



Before each trip down, the drill pipe column must be replaced and shackled, so that each pair of joints can get make-up and shackle operation in the process of three trips so that each joint thread can be inspected in time to reduce stickiness. The occurrence of problems such as buckles, trips, and punctures. At the same time, the positions of the upper and lower drilling tools should be switched regularly to change the stress state of the drilling tools, so that the stress of each part of the whole set of drilling tools tends to be consistent, so as to improve the service life of the drilling tools and reduce the early stage of the drilling tools. The occurrence of failure accidents. picture



During the drilling process, a reasonable rotation speed and WOB should be selected according to the formation, well diameter, and configuration of the lower drilling tools, so as to ensure that the drilling tools are in an ideal working state and obtain satisfactory drilling efficiency. When the rotation speed of the drill pipe reaches the critical speed, and the three vibration frequencies of longitudinal, lateral, and torsional vibrations generated by the rotation of the drill pipe are consistent with the natural frequency of the drill pipe itself, resonance will be induced, and the entire drill string in the hole will be in serious loss. a stable state, and make it withstand additional fatigue stress, thereby accelerating the fatigue failure of the drilling tool; the greater the WOB, the greater the resistance of the bottom hole bit, and the situation of stuck drilling is prone to occur. When the critical WOB is reached, the drilling tool will bend, resulting in a good deviation and the fatigue fracture of the lower drilling tool thread.



When the drill pipe is operated in a corrosive environment, oxygen scavengers and corrosion inhibitors can be added to the drilling fluid; the PH value of the drilling fluid can be increased to above 10; the sulfur-resistant drill pipe shall be selected; On the premise of meeting the strength requirements, the corresponding measures such as low-grade drill pipes should be selected as much as possible to reduce the influence of corrosion factors on the drilling tools.



When disassembling the drill pipe at the wellhead, the low gear should be used at first, and the hook spring should maintain a certain tension to ensure that there is no pressure between the threaded surfaces of the two joints. After the joint thread is completely disengaged, the hook is lifted up to prevent the thread from being pulled, which can also prevent the upper drill pipe from impacting and bumping against the wellhead female joint under the action of the spring force.



Maintenance and management of drill pipe after use:

After the drilling operation is completed, the drilling tools are neatly placed on the drill pipe frame according to different specifications, wall thicknesses, water hole sizes, steel grades, and classification grades. Thoroughly clean, rinse and dry the inner and outer surfaces of the drilling tools, joint threads, and shoulder sealing surfaces with clean water in a timely manner. Check whether there are cracks or nicks on the surface of the drill pipe, whether the thread is intact, whether the joint is eccentric, whether the shoulder surface is flat and scratched, whether the pipe body is bent or squeezed and whether the inner and outer surfaces of the drill pipe exist. Corrosion, pitting, and other defects. If conditions permit, ultrasonic flaw detection should be carried out on the drill pipe body from time to time, and magnetic particle flaw detection should be performed on the threaded part to reduce the probability of failure accidents such as joint thread breakage and drill pipe body leakage. For drilling tools without problems, smear anti-rust oil on the thread and the sealing surface of the shoulder, wear a protective wire and take various protective measures.



The drill pipe in question should be marked with paint and stored separately on-site to prevent misuse. And repair and replace the drill pipe in question in time, so as not to affect the later construction operation. For drill pipes that are not stored in the open air for a long time, they should be covered with rain-proof sheets, and the corrosion conditions of the inner and outer surfaces of the drill pipes should be checked regularly to prevent moisture and corrosion.