Reverse circulation magnetic salvage device

Drilling and Production Technology ⊥Structure and Application of magnetic salvage device

Table of Contents

01. Magnetic Salvage Tube·Purpose

Magnetic salvage tube is a tool using to salvage small ferromagnetic objects such as drill bits, palms, cones, shafts, slip teeth, pliers teeth, hammers, oil, casing fragments, etc. That fall into the well during drilling and well repair operations. For magnetic salvage devices that can perform positive and reverse circulation, small non-ferromagnetic objects can also be salvaging.

There are many types of magnetic salvage devices. According to their working performance, they are divided into strong magnetic salvage devices and high-strength magnetic salvage devices. According to their circulatory direction, they are dividing into positive and reverse circulation magnetic salvage devices.

02.Magnetic salvage tube·Structure

Magnetic salvage devices are divided into two types: strong magnetic and high-strength magnetic. But there is no difference in structure, only the material of the magnetic steel is different.

1. Positive circulation type strong magnetic and high-strength magnetic salvage device

This salvage device consists of an upper joint, a gland, a shell, a magnetic steel, a core iron, a magnetic isolation sleeve, a guide shoe, etc., as shown in Figure 1-1.

magnetic salvage device
magnetic salvage device

Figure 1-1    Positive circulation magnetic salvage device

1-upper joint; 2-pressure cap; 3-shell; 4-magnet; 5-core iron; 6-magnetic isolation sleeve; 7-flat shoe; 8-milling shoe; 9-guide shoe

The upper part of the upper joint is a drill pipe buckle or other types of threads, which are using to connect drill pipes or other salvage pipes and wire ropes, etc.. And the lower part is connecting to the shell. The upper joint has water holes from top to bottom.

The shell is equipping with a pressure cap, a magnet, a core iron and a magnetic isolation sleeve, and the bottom is connecting to the guide shoe. There are three structural forms of the guide shoe: flat shoe, guide shoe and milling shoe. As shown in Figure 1-1, there is a shoulder in the inner hole of the guide shoe to press the magnetic isolation sleeve, core iron and magnet. There are several axial small holes on the pressure cap and the magnetic isolation sleeve. And there is a large annular space between the shell and the magnet as a circulation channel.

2. Local reverse circulation type strong magnetic and high-strength magnetic salvage devices

This salvage device consists of an upper joint, a steel ball, a pressure cap, a shell, a salvage cup, a magnet, a magnetic isolation sleeve, a core iron and a guide shoe, as shown in Figure 1-2.

Reverse circulation magnetic salvage device
Reverse circulation magnetic salvage device

Figure 1-2 Reverse circulation magnetic salvage device

1-Upper joint; 2-Steel ball; 3-Salvage cup; 4-Pressing cap; 5-Shell; 6-Magnetic steel; 7-Core iron; 8-Magnetic isolation sleeve; 9-Flat shoe

The upper part of the upper joint is a drill pipe buckle or other types of threads. Which are using to connect drill pipes or other pipe columns. The upper joint is welding to the shell. A salvage cup is welding to the upper part of the shell, and there is a conical hole at the upper end. The steel ball is placing here to become a one-way valve. Blocking the passage of upper mud into the cup cavity. The cup cavity (housing) is connecting to the outside of the tool. There is an annular space between the outer surface of the cup body and the shell. And there are more than ten small inclined holes at its lower end. There are pressure caps, magnetic steels, and core irons in the shell. In the middle is a water hole that goes straight into the cup.

It can be seen that when the steel ball sits on the cone hole. The circulating mud flows along the annular space outside the cup body through the small inclining hole to the bottom of the well. Forming a strong vortex. And then enters the cup cavity through the water holes of the gland. Magnetic steel, and core iron, and flows out of the tool body from the four large holes and returns to the ground. Thus forming a local reverse circulation effect.

03.  Magnetic Salvage Devices·Operation Principle

1. Working Principle

The Magnetic fishing tool is a device with the shell guide shoe and the core iron as two concentric annular magnetic poles. The magnetic path between the two poles is a non-ferromagnetic material area. So that the core iron and the guide shoe have a high magnetic field strength at the bottom. Because the magnetic path is concentric. The magnetic lines of force are radial and concentrated near the center of the lower end of the salvage device. Which can magnetize and adsorb small pieces of ferromagnetic objects at the center of the magnetic pole. This type of magnetic salvage structure will not cut off the magnetic path even if the large pieces of fallen objects attracted cross. The space between the core iron and the guide shoe. And can also absorb some small fallen objects in contact with it to achieve salvage.

For the salvage of non-ferromagnetic fallen objects. The ball can be thrown before approaching the bottom of the well, and the pump circulation can be turning on. With the help of the small hole jet effect of the high-pressure and high-speing circulating mud. The small fallen objects at the bottom of the well can be floated. And enter the nest with the returning mud. Since the ferromagnetic fallen objects are adsorbed. The fallen objects stored in the nest can no longer fall back to the bottom of the well. And the non-ferromagnetic fallen objects can be salvaging.

2. Calculation of suction gravity (magnetic loss is not considering)

According to the formula of magnetic energy force, the suction gravity P is:

P=(B/4963)²·S

Where,

B——magnetic induction intensity;

S——magnetic flux area.

From the above formula. It can be seen that the suction gravity P is affected by the magnetic field intensity B and the magnetic flux area S. However, the magnetic salvage is limiting by the working annular space. It can only take a certain value. So the important way to increase the suction force P is to select magnetic materials with high saturation magnetic induction intensity.

High magnetic permeability and low coercive force.

3. The influence of permanent magnetic materials on suction force

The Magnetic fishing tool relies on permanent magnets (magnetic steel) as the energy source for salvaging fallen objects. However order to obtain better salvage effect, it is requiring that the permanent magnet per unit area generates as much magnetic energy W as possible.

Briefly,The greater the coercive force H0 and the residual magnetic induction intensity Br, the greater the energy W in the magnetic circuit gap. For example, the size of the magnetic energy product is an important performance indicator of the magnetic salvage device.

So a result,In other words, due to the different weights adsorbed by different permanent magnetic materials. There is a difference between strong magnetic type and high-strength magnetic type salvage devices.

04. Magnetic salvage tube·Operation method

1. Preparation

  • (1) According to the well diameter and the characteristics of the fallen objects, select the appropriate guide shoe and salvage device.
  • (2) Place the salvage device on a wooden board or rubber, remove the steel ball and remove the magnetic protection plate. And check the tool size and whether the water hole is unobstructed.

2. Operation method

  • (1) Tighten the salvage device on the salvage drill string and go up and down the well.
  • (2) When the magnetic salvage device is 3~5m from the bottom of the well. Start the pump to circulate and flush the bottom of the well.
  • (3) After the bottom of the well is flushing. Slowly lower the drill bit while maintaining the circulation to touch the fallen objects. The drilling pressure should not exceed 10KN at this time. Then lift the drill bit 0.5~1m. Turn the salvage device 90° and repeat the above steps.
  • (4) If a reverse circulation Magnetic fishing tool is using, stop the pump after the positive circulation well is washing. Put in the steel ball, lower the tool to 0.5m from the bottom of the well, start the pump circulation. The displacement should be large, about 10~15 minutes. And then use different methods to salvage according to the selecting guide shoe.
  • If a flat shoe is using, it is necessary to circulate, lower and rotate the drill bit. And repeat it up and down several times.
  • (5) Confirm that the fallen objects have been sucking up, lift the drill bit 0.5~1m, stop the pump, and start drilling.

05 Magnetic salvage tube·Precautions

1. Precautions

  • (1) Before the magnetic salvage device enters the well. It must be separating from other ferromagnetic equipment by wooden boards or rubber sheets.
  • (2) When removing the magnetic protection plate and the attracted objects. The operator’s force should be perpendicular to the center line of the tool.
  • (3) The operator is not allowed to hold ferromagnetic hand tools close to the bottom of the magnetic salvage device to prevent injury.
  • (4) Avoid severe vibration and collision during transportation and loading and unloading.

2. Maintenance

  • (1) After leaving the well, wash with clean water to remove the tiny ferromagnetic substances on the surface of the core iron and magnetic steel. Medical adhesive tape can be using to adhere to extremely tiny particles.
  • (2) Oil the threads of each joint, rinse each water hole and circulation channel, and replace damaged parts.
  • (3) Store in a dry place.

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