Application of the hottest frequency converter in

2022-08-24
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Application of frequency converter in domestic oil drilling rigs

1 Introduction to drilling technology

the drilling process is divided into several major processes, such as lifting and lowering the derrick, drilling, mud circulation, drilling tool replacement, casing running, logging and so on. It is mainly divided into winch, rotary table and mud pump. The winch is composed of drum, gearbox, clutch, brake, motor and control equipment, which is used to lift and lower the derrick, drill pipe and casing. With the increase of well depth, the drilling tool becomes longer and longer, the weight increases rapidly, and the load of winch becomes larger and larger. At present, there are 7000m deep oil wells in China, and their drilling tools weigh nearly 600t. Due to its anti ash and anti fouling redeposition properties, the drill pipe needs to be lifted and lowered once every 9m, so the winch operation time accounts for an increasing proportion of the whole operation time with the increase of well depth. In order to reduce costs, it is hoped that the shorter the operation time in the field or at sea, the better. This not only requires the winch to operate at a high speed and start and stop smoothly, so as to ensure that the drilling equipment is not damaged and improve the quality of the well, but also requires the driving equipment to have good dynamic characteristics. If working in the internal well area, the power supply can be connected with the electricity in the well area. When lowering the drill pipe, the motor works in the power generation state, and the energy can be fed back to the electricity, which has a significant energy-saving effect

the rotary table and winch can share the same set of drive system and motor. After the drill pipe is lengthened, the drive part is switched to the rotary table, and the rotary table drives the drilling tool to rotate to implement the drilling operation. The driller changes the drilling speed by adjusting the rotary speed and pressure of the rotary table. When the rotary table works normally, it turns forward. When dealing with sticking, it needs to reverse to recover the drill bit. In order to prevent the drill pipe from breaking during forward rotation or tripping during reverse rotation, the output torque of the motor is required to be stable, the adjustment is flexible, and the limit amplitude is set. At the same time, the brake components of the motor are also essential

the mud pump is equivalent to the heart of the whole drilling equipment, and the mud it outputs is similar to the blood in the human body. Mud is injected from the inside of the drill pipe from top to bottom. After flowing through the drill bit, it flows out from the gap between the drill pipe and the well wall from bottom to top. In this process, mud assists the drill bit to impact the crust, cool the drill bit, and bring out debris. More importantly, by infiltrating barite powder and other substances into the mud, a certain pressure can be maintained underground to avoid blowout, such as blood circulating in the human body, transporting nutrients, and taking away waste. The pressure and stroke of the mud pump are respectively proportional to the output torque and speed of the drive motor

the schematic diagram of winch load is shown in Figure 1

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2 system configuration

in 1998, we configured a frequency converter for a set of drilling equipment with a depth of 3200m of the drilling company of Xinjiang Petroleum Administration Bureau. The product used is Siemens simovertmasterdrives6se71 voltage source frequency converter cabinet.

the power system is composed of 3 × It is composed of 800KW diesel generator set, with 3 units in 3-phase, 600v/50hz AC bus

the transmission part is composed of 3 × 6se7141 rectifier cabinet (3 × 800KW) power supply to public DC busbar, 4 × 6se7135 inverter cabinet (4 × 400KW) and 2 × 6se7136 inverter cabinet (2 × 450KW) a total of 6 inverter cabinets are connected to the DC busbar, and each inverter cabinet drives a 400KW motor. Four motors, two in one group, drive two mud pumps in total, and the other two motors are shared by winch and rotary table. See Figure 2 for details

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1) the power supply is powered by a diesel generator, which requires sufficient voltage stability and frequency stability. The rated capacity of the diesel generator is generally less than the capacity of the transmission device. 1. The measurement of the force value of the tensile test machine is completed through the force measuring sensor, expander and data processing system. From the perspective of data mechanics, under the condition of small deformation, the strain at a certain point of an elastic element ε It is directly proportional to the force on the elastic element and also directly proportional to the elastic deformation Taking the sensor of S-type experimental machine as an example, when the sensor is subjected to the effect of tension P, because the elastic element is pasted with a strain gauge on the surface, and because the strain of the elastic element is in direct proportion to the size of the external force P, the strain gauge is connected to the measuring circuit, and then the output voltage can be measured, and then the size of the output can be measured 5-10 times, belonging to "small electricity" power supply, with large commutation gap. Simovertmasterdrives6se71 frequency converter can maintain the waiting time of main circuit voltage for 2~3s to overcome the transient power failure and commutation gap of diesel engine

2) according to the transmission of multiple motors, the common DC busbar scheme is adopted, so that if one transmission device works in the power generation state, energy exchange can be carried out through the intermediate circuit, and only one total braking resistor is used

3) a self oscillating diode is equipped on the DC busbar to prevent overvoltage on the busbar and affect other inverters when the DC side fuse on one inverter is disconnected or energy is fed back. In addition, this kind of material is called microporous foam, and there is a vdmax regulator in the internal software of the inverter to prevent the DC busbar from tripping due to overvoltage

4) compared with the transmission of a single frequency converter, the installation size is smaller, because side components, such as fuses, contactors, switches and side incoming reactors, can be used once. The mechanical structure has taken measures to adapt to the harsh environment on site

5) the selected inverter has the same power and can be set with 4 sets of given array and motor array, which can be easily switched to each other and used as standby in case of fault. With the switch of winch/rotary table, the automatic conversion of current limiting and the whole set of control data can be realized

6) optical fiber fast (11mbit/s) communication and dual speed loop scheme are adopted between two frequency converters of the same equipment. Under the condition of no encoder feedback, the safety is effectively guaranteed, and the static deviation of the load current of the two motors driving one equipment is less than 1%, which is far better than the 10% specified in the national standard of the drilling rig. Here are some detailed control schemes we taught our customers. See Figure 3 for details

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7) if the drilling rig can be connected to large electricity, it can be considered to feed back electricity through electric energy, but the stability of electricity should be confirmed in advance to avoid overcurrent of inverter bridge during electric wave motion.

the drilling rig adopts winch and rotary table combined drive

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