Workover rig is a necessary equipment for oilfield workover operation, among which derrick is the key component of oilfield workover rig for replacing tubing and sucker rods. The derrick of the workover rig is generally a mast-type derrick with a telescopic rod type, and the working load it bears is relatively complex. Loads generated when rods and tubing.

Based on the JJ135/33 derrick commonly used in Daqing Oilfield for 80t and 100t workover rigs as an example, this paper analyzes the structural characteristics of this type of derrick, simplifies the complex derrick structure, determines the initial working conditions, defines different types of loads, and creates a finite element of the derrick. working model.

The ANSYS finite element strength analysis is carried out on the JJ135/33 derrick under three working conditions, namely, working, expected and unexpected, so as to obtain the displacement and stress state under the given load. The position of stress concentration of the derrick is determined by analysis, the structure of each part of the derrick is optimized, and the influence of the upper body necking angle, the selection of derrick materials and profiles is analyzed.

By optimizing the structure of the derrick, it can not only reduce the raw materials, but also reduce the weight of the derrick, so as to obtain the optimal economic benefits, and at the same time, the reliability can be improved.

As a typical rod structure, buckling stability analysis and modal analysis are carried out on the derrick. The buckling analysis checks the column stability and the overall stability of the derrick under the maximum hook load condition. The modal analysis uses ANSYS to analyze the first 8 order natural frequencies and formations of the derrick under its own weight.

The finite element strength analysis method can simplify the calculation process, thereby improving the design efficiency and saving time. Based on the analysis results, a reasonable product structure is determined, which not only reduces the cost, but also improves the reliability of the derrick.

In the construction of oil and gas exploration and development, workover is an important link. In the process of oilfield operation, downhole oil production equipment often has equipment failure. After the fault occurs, only through the downhole operation to remove the fault, replace the equipment and adjust the oil well parameters, can the oil well production be restored. As an important basic mechanism of the workover rig, the derrick is used to take off and lower the tubing It plays an important role in underground operation.

At present, in workover operation, it is common to adjust the derrick guide rail to the wellhead manually, which has the advantages of low adjustment accuracy, time-consuming and high work intensity. The guide rail support has problems such as heavy design, low adjustment efficiency, poor accuracy, and high work intensity of workers. Long time use of this derrick structure not only takes time and energy, but also greatly affects the service life of workover rig.

To solve this problem, Sanjack group independently developed a new type of multi-functional derrick. By adjusting the rigid guide rail, the stability and accuracy of wellhead calibration are improved, the adjustment time of guy rope is reduced, and the work intensity of workers is reduced, thus the problem is solved perfectly.


The new multi-functional derrick includes U-shaped derrick, rigid guide rail, triangular support frame between U-shaped derrick and rigid guide rail, etc., as shown in the following figure:

And in order to achieve the desired purpose, we adopted the following design scheme: the triangle support frame is equipped with adjusting lead screw, the drum is installed on the U-shaped derrick, and the drum is connected with the adjusting lead screw by wire rope; there are two wire ropes, the upper ends of the two wire ropes are respectively connected to the two ends of the adjusting lead screw, two fixed pulleys are set on the U-shaped derrick, and the position of the two fixed pulleys is higher than Adjust the lead screw, two wire ropes respectively bypass their respective fixed pulley, the lower ends of the two wire ropes are wound on the same drum, but the winding direction is opposite. The triangular support frame includes a tripod body, an articulated seat is arranged at the top of the tripod body, and an articulated hole is arranged at the upper end of the hinged seat to hinge the rigid guide rail. The lower end of the hinged seat is threaded through the mounting hole at the top of the tripod body in the form of a bolt, and the bolt body of the hinge seat is sheathed with a damping spring and fixed with a nut. There are two relatively symmetrical guide wheels at the bottom of the tripod body. The U-shaped derrick is equipped with rails, and the guide wheels are rolling on the rails.


Compared with the prior art, the utility model has the following beneficial effects:

A drum is set on the U-shaped derrick, and a triangular support frame is set between the U-shaped derrick and the rigid guide rail to connect it, so as to realize the adjustment of the rigid guide rail

1). improve the stability and accuracy of aiming at the wellhead

2). reduce the adjustment time of the guy rope

3). reduce the work intensity of the workers.

Stability analysis of the derrick column and the derrick as a whole, and master the ballast stability analysis of long and thin rods methods. Through the modal analysis of the derrick, the relationship between the natural vibration frequency of the derrick structure and the period of the external load is understood, and it is judged that when the structure is subjected to an external load, the natural frequency of the derrick is very different from the vibration disturbance frequency of the turntable.

The influence is small, and the two front columns of the derrick have poor torsion resistance. In order to intuitively analyze the vibration state of the structure, find out the reasons for the structural vibration and its weak links, and thus lay a certain foundation for the improvement of the structure.