26. Расскажите о процедуре установки пакера

Uses of packers

In addition to providing a seal between the tubing and casing, other benefits of a packer are as follows:

• Prevent downhole movement of the tubing string

• Support some of the weight of the tubing

• Often improve well flow and production rate

• Protect the annular casing from corrosion from produced fluids and high pressures

• Provide a means of separation of multiple producing zones

• Limit well control to the tubing at the surface for safety purposes

• Hold well-servicing fluid (kill fluids, packer fluids) in the casing annulus.

Packer components

Packers have four key features:

• Slip

• Cone

• Packing-element system

• Body or mandrel.

The slip is a wedge-shaped device with wickers (or teeth) on its face, which penetrate and grip the casing wall when the packer is set. The cone is beveled to match the back of the slip and forms a ramp that drives the slip outward and into the casing wall when setting force is applied to the packer. Once the slips have anchored into the casing wall, additional applied setting force energizes the packing-element system and creates a seal between the packer body and the inside diameter of the casing.

27. Устранение аварий обсаженном стволе

Milling

Milling operations are carried out to clean the well from obstacles that cannot be removed with the bit:

• bridge plug

• cement retainer

• packers

• metal objects that have fallen to the bottom

• stuck strings

Milling cutters

Milling cutters are used for milling operations. A milling cutter is a rugged tool but it is very fragile; it is basically used as a lathe machining tool: high number of revolutions and scarcely loaded. The operating performances of a milling cutter are based on the preparation method (coating and tempering application) and on the usage procedures.

Milling

Never start milling with a mill set against the obstacle:

• Approach the obstacle with the string rotating and without circulation, then determine its exact depth

• Lift the string

• Start circulating at a low rate: high rates may damage the mill

• Set the required number of revolutions (60 - 100 RPM) and check the weight of the string

• Gently approach the object to be milled

• Unload 2 – 8 tons and then continue without producing vibrations

• Always check the torsion indicator (if any)

Variation of parameters

To change any parameter:

• Stop rotation

• Lift the string

• Reset the system under operating conditions and restart as above

The mill can be modified during operations so as to monitor the situation as it evolves. By

examining the mill that has been pulled out, it is possible to obtain useful indications on how to

use the next one.

Milling string

A junk sub, located just above the mill, shall be inserted in the milling string. It is used for

collecting the biggest parts of the milled material, thereby preventing blockage at the bottom ofthe well. During milling operations, the string shall be stabilized in order to minimize damage tothe casing. A jar must always be inserted into the string but never insert a bumper.

Milling fluid

Milling fluid is very important because its viscosity must be able to keep the milled material insuspension. Insert a magnet in the mud circuit upstream of the shaker in order to recover junkfrom the mud coming out of the well. Use viscous fluid cushions to clean the bottom. Using oil base mud could make milling operations more difficult.