28. Борьба с солеотложением

Removal of Paraffin, Saline Deposits or Asphaltene

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• Paraffin deposits are caused by a decrease in the oil temperature between the bottom and the head of the well.

They represent a serious problem in oil wells.

• Using the coiled tubing it is possible to remove the paraffin by circulating hot oil or hot water at the bottom, so that the tubing regains its original internal diameter

• Saline deposits can also be a problem, but since they are water soluble, a bottom circulation with hot water will be very effective.

• Note: In case of paraffin or saline deposits, special chemicals can be used to restore the tubing working conditions.

• Asphaltene belongs to the category of bitumen, and the oils that contain a high concentration of it, tend to deposit it along the tubing walls.

• In case of presence of asphaltene, wireline operations become impossible, because the toolstring and the running/pulling tools are coated with viscous and semisolid bitumen, that hinders their movements.

• Note: Asphaltene can be removed also by pumping organic solvents (such as xylene, toluene or OLG), but the effects of the pumping action are limited in time.

• With the coiled tubing it is possible to carry out efficient mechanical and/or chemical washings.

30. Ловильные работы в скважине

• Fishing Operations

Fishing is a heavy workover operation that is carried out to rectify incidents occurred in the well during:

_ Completion

_ Production

_ Workover

• Conditions requiring fishing operations

Fishing operations shall be carried out when the following occurs:

_ failure of the string (pipes and tubing)

_ unfeasibility to release the packer(s) when pulling out the completion equipment

_ recovery of objects that have fallen in the well

_ string getting stuck:

_ during plugging or cement squeezing

_ when running-in a packer that gets stuck

_ when pulling out a packer that gets stuck due to deformation of the column or to a slip

coming out or objects falling in the well

• Fishing recommendations

When approaching the fish:

_ run in slowly with very slow circulation

_ Once the fish is caught, stop the pump

_ release according to the type of fisher

It is recommended to insert a safety joint in the string, right above the fisher Insert the jar into the string