Analysis on the current status and development direction of direct drive technology for oil drilling winches

introduction

With the development of automation and intelligence of oil drilling equipment, traditional multi-stage drive winches have gradually failed to meet the supporting requirements of existing drilling rigs due to their complex structure, large size, low transmission efficiency, high maintenance cost, poor inherent safety and other factors. In recent years, direct drive technology has been rapidly promoted in the field of oil drilling and production, and it is mainly used in winches, rotary tables, mud pumps, top drives, automated machinery and other equipment.

This paper focuses on the application of direct drive technology in the field of drilling winches and puts forward some opinions.

1. Requirements for winches in oil drilling

The oil drilling winch is a multifunctional lifting machine, and its working nature is different from that of general lifting equipment. To study the direct drive technology of oil drilling winch, it is necessary to analyze the requirements of oil drilling operations for winches according to drilling conditions.

(1) Sufficient lifting capacity: During the drilling process, the drilling winch is used to lift and lower the drilling tools. In order to meet the operational requirements of the maximum hook load, it should have sufficient lifting capacity.

(2) A wider speed regulation range: According to the drilling operation conditions, each time a vertical root is lowered, the empty hook needs to move up quickly, grab the drill bit again and continue to lower it. In addition, in order to improve the operation efficiency, the drilling winch needs to have a wider speed regulation range according to different loads without losing its lifting capacity.

(3) Lifting and lowering the derrick base: Use the winch as the power source to complete the lifting and lowering of the derrick and base.

(4) Emergency accident handling capability: Always have the ability to move drilling tools, unblock stuck holes, and handle complex underground accidents.

(5) Ultra-low frequency precision control of automatic drilling: During drilling, the drill bit is suspended and constant drilling pressure or constant drilling speed is achieved to precisely control drilling.

(6) Casing installation: After drilling, casing installation is required to quickly complete cementing and improve completion quality.

(7) Emergency plan: In terms of operation safety, once the winch fails, the entire operation process will be basically interrupted, and even a major safety accident may occur. Therefore, the winch must also have high reliability, sensitive control system, and safe braking system. At the same time, in the event of failure of the main motor, electronic control, etc., it should have emergency lifting and movable drilling tool functions.

2 Current status of direct drive technology for oil drilling winches

In recent years, direct drive technology has developed rapidly, which has promoted the development of direct drive technology for oil drilling equipment. Lanshi Group started to study and apply winch direct drive technology early. In 2005, when Lanshi was developing helicopter hoisting drilling rigs, it took the lead in developing direct drive winches, using asynchronous motors to directly drive the drum shaft, but due to the limitations of motor technology and control technology, it was not industrialized. Subsequently, the researchers changed their thinking and developed a semi-direct drive winch, hanging a large gear at one end of the drum shaft, hanging a small gear at the head of the asynchronous motor shaft, using a first-stage reduction device, and removing the gear transmission box. This solution can simplify the winch transmission system, eliminate motor technology limitations, meet the requirements of drill delivery control accuracy, reduce energy loss during drill delivery, and meet helicopter hoisting requirements.

Baoji Petroleum Machinery Plant widely uses direct drive technology on JC30~90 winches, all of which are driven by asynchronous motors. The motors are arranged on one side or both sides of the drum shaft and connected to the drum body through a drum-shaped gear coupling, as shown in Figure 1. Its technical features are: simple structure, small disassembly and assembly workload; compact layout, neat and beautiful; high transmission efficiency and less maintenance.

Honghua has successively applied direct drive technology on JC40~70 winches, all of which use single asynchronous motors or dual asynchronous motors to directly drive the drum, without a deceleration shift mechanism or coupling, and directly integrate the motor stator with the winch wall panel, as shown in Figure 2. Compared with traditional winches, its volume is 40% smaller, its weight is 25% lighter, and the maintenance workload is reduced by 70%~80%.

Figure 1 BOSS direct drive winch

Figure 2 Honghua direct drive winch

3. Permanent magnet direct drive winch technology

At present, direct-drive winches all use asynchronous motors instead of permanent magnet motors. The reason is that oil drilling has extremely high requirements for the reliability and safety of winches. At the same time, drilling winches need to have large acceleration, high operating speed, ultra-low frequency operating stability, and continuous performance improvement under large loads under different working conditions. As shown in Figure 3, due to the physical properties of the material, as the temperature rises, the magnetism of the permanent magnet will drop rapidly, and even demagnetization may occur.

Figure 3 Curve of permanent magnet magnetic properties changing with temperature

In addition, the comprehensive test of the output of the permanent magnet motor's magnetic field, temperature field, fluid field and mechanical performance is the result of the mutual influence of multiple physical parameters and the mutual optimization of multiple objective parameters, as shown in Figure 4.

Figure 4 The mutual influence relationship of multiple physical parameters of permanent magnet motor of oil winch

4. Asynchronous direct drive winch test

Under the premise of meeting the performance of the equipment, the purpose of direct drive is to reduce the transmission chain, improve the transmission efficiency, and improve the economy of the equipment. The following efficiency tests of different winches are carried out (Figure 5, Table 1), and the following conclusions are drawn: the permanent magnet direct drive winch has the highest efficiency under the same load, followed by the asynchronous semi-direct drive winch, and finally the asynchronous direct drive winch: At the same time, when the load is reduced, the efficiency of the asynchronous direct drive winch decreases greatly, and the semi-direct drive and permanent magnet direct drive winches decrease less, reflecting that the asynchronous direct drive has a higher energy consumption under heavy load, and the asynchronous direct drive has an even higher energy consumption under high speed and light load. The asynchronous direct drive consumes a lot of energy when working for a long time under ultra-low speed drilling. As mentioned in the previous article, permanent magnet direct drive has not been used in oil drilling winches, so it will not be discussed here.

5 Industrial test verification

The author has investigated the industrial applications of 19 direct-drive winches in different working conditions and at different levels. Their comprehensive energy consumption, equipment cost, control cost, drilling performance and maintenance cost are all higher than those of semi-direct-drive winches, especially for large-scale direct-drive winches, whose comprehensive energy consumption increases significantly. The results are shown in Table 2.

According to industrial application verification, the technical and economic indicators of asynchronous direct drive winch and traditional winch are analyzed, and the following conclusions are drawn:

Asynchronous direct-drive winches have the advantages of light weight, small size, and low maintenance cost, but they have the following problems: (1) The installed power is large and the motor energy consumption is high; (2) The inverter supporting power is increased and the electronic control cost is high; (3) The ultra-low frequency control accuracy of the main motor is low, resulting in poor stability of automatic drilling and large fluctuations in drilling pressure; (4) The working noise is loud. Due to the high heat generation, a single winch is equipped with 4 fans for forced cooling, and the winch has a whistling sound in some speed ranges; (5) The emergency plan is insufficient.

The semi-direct drive winch has the advantages of high efficiency, light weight, small size, low maintenance cost, very stable drilling performance, low control manufacturing cost, low energy consumption, and emergency plan.

6 Suggestions on the development of direct drive technology for oil drilling winches

Although my country has made certain breakthroughs in the field of direct-drive technology for oil drilling winches, its economic indicators cannot meet market requirements for the time being, which is one of the main reasons for its slow progress.

Based on the comprehensive needs and market orientation, the author puts forward the following suggestions: (1) Develop a new type of direct-drive motor to improve its safety, reduce installed power, and reduce power loss during light-load operation; (2) Improve performance, improve ultra-low frequency control accuracy, and reduce self-energy loss during long-term ultra-low frequency operation; (3) Optimize the main structure and consider using water cooling for cooling [4] to reduce working noise; (4) Improve the basic industrial R&D and manufacturing capabilities, promote the development concept of semi-direct drive winches, and promote the development of automation and intelligent technology for petroleum equipment.