What is drill pipe?
Drill pipe is an important part widely used in the oil drilling and production industry. During the drilling process, as the drill bit goes deeper, the drill pipe needs to be added piece by piece. Both ends of the drill pipe are machined with internal and external threads respectively, and are connected piece by piece through threads. It is also possible to have external threads on both ends of the drill pipe and connect them piece by piece through couplings with internal threads on both ends. The entire drill pipe consists of a pipe body and drill pipe joints that are connected to both ends of the pipe body (usually by friction welding). Drill pipe is the main tool in oil and gas drilling and geological survey, and is made of seamless steel pipe. It is used to connect surface drilling rigs and equipment such as drill bits at the bottom of the drilling well, to transmit power and transport drilling fluid and mud, and to lift, lower or rotate the drilling and grinding equipment at the bottom. At the same time, the high-pressure cleaning fluid also Flows to the bottom of the well through the inner hole of the drill pipe. During the service process, oil drill pipes are not only affected by the complex underground environment, but also undergo a variety of alternating stresses, such as tension, compression, torsion, bending, impact, etc.
What types of drill pipe are there?
Drill pipe can be divided into three categories:Square drill pipe, platform drill pipe and weighted drill pipe:
(1) Square drill pipe: Square drill pipe is located at the top of the drill string and comes in two types: square and hexagonal. It has the following functions: first, when drilling, the square drill pipe cooperates with the core filler and the turntable core filler to transmit the ground rotation torque to the drill pipe to drive the drill string and drill bit to rotate; second, it bears the entire weight of the drill string. Channel for drilling fluid circulation.
(2) platform drill pipe: the basic component of the drill string. Its main function is to transmit torque and transport drilling fluid, and to continuously deepen the wellbore by gradually lengthening the drill pipe. Therefore, drill pipe plays a very important role in oil drilling.
(3) Weighted drill pipe: Weighted drill pipe is similar to oil drill pipe. It is also a hollow steel column with a length of about 10 meters. However, a single piece of weight is heavier than the oil drill pipe, and the wall thickness is 23 times that of the drill pipe. The weighted drill pipe is connected between the drill pipe and the drill collar to prevent fatigue damage due to changes in the cross-section of the drill string. Use it also It can replace part of the role of drill collars, but it is simple to hoist and easy to trip out, which can save tripping time.
There are three types of drill pipe joints according to different inner diameters:
(1) Regular joint: The inner diameter of the joint is smaller than the inner diameter of the inner thickened drill pipe and the outer drill pipe. The mud flow resistance is larger but the strength is higher than other types of joints.
(2) Through-hole joint: The inner diameter of the joint is similar to the inner diameter of the drill pipe after adding Hanoi. There is little resistance when the mud flows, and the flow rate does not change significantly.
(3) Internal flat joint: The inner diameter of the joint is similar to the inner diameter of the external drill pipe, and the mud flow resistance is minimal. Therefore, it is mostly used for small drill pipes. In order to fully utilize the water horsepower in turbine drills and screw drills, internal flat joints are often used.
Drill pipe production process
The production process of drill pipe can be roughly divided into blanking, rough turning, modulated heat treatment, thread machining, ammonia treatment, friction welding, spraying, and packaging. In the entire processing process, modulated heat treatment and friction welding processes are important links that affect the performance of drill pipes.
Conclusion
During the drilling process, the weight on bit is formed by the weight of the drill string (connected by drill pipes), so the lower part of the drill string is subject to compressive stress. When drilling, the value of the drilling pressure is generally greater than the stability critical value of the pressure rod of the drill string, so the lower pressure-bearing part of the drill pipe will bend under its own weight. The bent drill string will cause alternating stress during rotation, leading to fatigue failure of the drill string. In order to reduce the degree of fatigue damage, the bending stress should be reduced. This requires shortening the length of the pressure section as much as possible and increasing its rigidity. Therefore, drill collars are used instead of drill pipes for the pressure-bearing part of the lower end of the drill string. As the underground environment of coal mines continues to become more complex, people's performance requirements for drill pipes are gradually increasing. Due to the continuous application of mine drilling technology, drilling costs and drilling risks are also increasing. Traditional drill pipes can no longer meet the requirements. The new generation of drill pipes is developing towards high strength, high toughness, anti-corrosion, safety and environmental protection. For example, drill pipes will continue to be intelligent, and the transmission data rate and temperature resistance will be further improved.