Drill collar is a kind of seamless steel pipe with thicker wall and larger weight per unit length than ordinary drill pipe. It is made of higher strength steel. The drill collar is connected to the drill pipe with a threaded thread on the top and the drill bit on the bottom. Its main function is to use its own weight to provide drilling pressure for the drill bit to break the rock and achieve drilling. Different sizes of drill jacks should be selected according to the size of the drill bit. The drill collar is located between the drill bit and drill pipe or weighted drill pipe in the drill tool assembly. Its main function is to provide drilling pressure to the drill bit and control the well deviation. Drill collar sizes range from 31/8 to 11 inches, and the heaviest drill collar can weigh up to 300 kilograms per meter. There are thick female buttons at both ends of the drill collar. Some have a female button on one end and a male button on the other. In order to eliminate stress concentration and avoid fatigue damage of the drill collar, stress relief grooves are opened at both ends of the drill collar body near the joint threads.
The structure and composition of drill collars
The drill collar of oil drilling tools usually consists of drill bits, drill strings, drill pipes, etc. The main part of the drill collar is the drill bit, which is located at the end of the drill string and is the component that directly contacts the formation and performs drilling operations. Drill bits are usually made of alloy materials, which are wear-resistant and corrosion-resistant to cope with the high pressure, high temperature and hardness of various rocks in the formation.
The connecting threads at both ends of the drill collar are tapered male and female buttons. Drill collars can be divided into three types according to their appearance and materials: Type A (cylindrical), Type B (spiral), and Type C (non-magnetic), represented by the codes ZT, LT, and WT respectively. His three categories will be introduced below:
Non-magnetic drill collar
The structure of non-magnetic drill collars is the same as that of ordinary drill collars, but their chemical composition and mechanical properties are different from ordinary drill collars. Non-magnetic drill collar is a drilling tool with special functions in directional engineering. When orienting and using a magnetic inclinometer to measure the parallel eye inclination angle and azimuth angle, in order to prevent the compass from being affected by the magnetic field of the drill string, a certain length of non-magnetic drill collar must be equipped in the drill string so that the magnetic inclinometer is located in the non-magnetic drill string. Measure the inclination at the appropriate position inside the collar, otherwise the correct measurement results cannot be obtained.
Spiral drill collar
The spiral drill collar can reduce the contact area with the well wall. The shallow and wide spiral groove can reduce the contact area by 40% to 50%, and its weight is reduced by 7% to 10%. Smaller contact area reduces the possibility of differential pressure stuck. Therefore, it has been widely used in modern drilling.
Cylindrical drill collar: Made of ordinary alloy steel, the cross section of the tube body is round both inside and outside.
The functions and functions of drill collars
(a) Drilling into the formation:
One of the main functions of oil drilling tools is to drill into the formation and detect underground oil and natural gas resources. The drill collar rotates and advances to place the drill bit below the wellhead and gradually drill down into the formation. In this process, the drill collar needs to overcome the resistance of the formation to reach the predetermined drilling depth.
(b) Transmitted torque and speed:
The drill collar also plays the role of transmitting torque and rotational speed. By rotating the drill collar, the drill bit can quickly cut rocks in the formation and lift formation samples to the surface. At the same time, the drill collar needs to transmit sufficient torque and rotational speed to ensure the stability and efficiency of the drill bit during the drilling process.
(c) Load carrying:
During the drilling process, the drill collar also needs to withstand the weight load from drilling fluid, drill string, drill bit and other components. This requires the drill collar to have sufficient strength and rigidity to ensure that it does not deform or break under high loads.
(d) Transfer drilling fluid:
There are usually pipes inside the drill collar for transferring drilling fluid. Drilling fluid plays the role of cooling, lubricating, straightening and cleaning the bottom of the well during the drilling process. Therefore, drill collars need to ensure that the drilling fluid can be effectively transported from the surface to the bottom of the well, and drill cuttings and cuttings can be brought back to the surface.
With the continuous development of the petroleum industry and the advancement of technology, the drill collars of petroleum drilling tools are also constantly evolving and improving. In the future, the development trend of drill collars will be on the rise. Our company has always been adhering to the principle of quality first, pursuing excellence in production technology, reasonable pricing, and adapting to the new needs of oil exploration and development. If you need it, please feel free to submit an inquiry at any time.