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Check Valves

Wireline fishing

centre spear for wireline fishing

Fishing is the name given to the operation to retrieve items from the well which may be damaged, stuck, or have been dropped, and is an efficient way of rectifying these kind of problems.

The most common reason for fishing is when a wireline has broken either at surface and remains visible or downhole and not visible. In the latter case several conditioning and preparatory trips may be necessary before the ‘fish’ can be located successfully and retrieved. As each fishing job is different these operations cannot be covered by specific procedures, but it is in this area the operator’s experience and skill can play a significant part.

Wireline fishing is not a planned operation, the variety of possible fishing jobs make it impossible to obtain definitive procedures. However, it should be remembered that, standard wireline procedures and practices must still be followed wherever possible even when the rig up will almost certainly be different from normal.

Fishing techniques are extremely varied and depend largely on the circumstances and well conditions for each individual situation.

The following are some of the causes of a slickline fish:

  • Bending stresses
  • Lack of control when jarring
  • Tool string entry into lubricator
  • Exceeding safe limits of wire strength
  • Unclear verbal communication
  • No proper equalisation
  • Defective fishing neck
  • Tools backed off.

Slickline sizes

Slickline is manufactured in a variety of sizes and materials. The common ones are shown below.

When carrying out wireline operations it is absolutely necessary to use specific mechanical equipment, such as the reel drum, hay pulley, stuffing box pulley and measuring wheel. Each time the line passes over a pulley it is subjected to two bending stresses when it changes from a straight to a curved path and again when it reverts to a straight line.

 

Nominal

Diameter ins

Nominal Nett

Weight per 1,000ft
lbs

Rec Min Pulley

Diameter ins

Minimum Breaking Load

Bright

 

 

 

lbf

 

lbf

 

 

0.108

31.23

13.0

2,110

2,730

0.125*

41.84

15.0

2,830

3,665

* A non-API standard size.

Table 1 – Carbon Steel Wirelines To API 9a

 

Nominal Diameter

ins

 

 

304

lbf

 

 

316

lbf

 

 

18/18/2

lbf

 

 

Supa 70

lbf

 

 

Supa 75

lbf

 

 

Supa 80

lbf

 

0.108

2,100

1,920

1,720

2,100

2,030

2,175

0.125

2,700

2,500

2,600

2,560

2,775

Table 2 – Minimum Breaking Load

 

Steel

 

Specifications

Strength Relative To

API 9A

General Corrosion

Resistance Rating

Carbon steel

API 9A

API 9A

Poor

Ultrahigh tensile

Bridon UHT

25% higher

Poor

Stainless special alloy:

 

 

 

 

304 type

 

Bridon

 

API 9A

Good – not in chlorides

 

316 type

 

Bridon

 

10% lower

Better than 304 in very low chlorides

 

18/18/2

 

Bridon

 

20% lower

Better than 304 higher resistances to chlorides

 

Supa 70

 

Bridon

 

Similar

Good in H2S, CO2

and chlorides

 

Supa 75

 

Bridon

 

5% lower

Good – better than

Supa 70

 

Supa 80

 

Bridon

 

3% higher

Good – better than

Supa 75

Table 3 – General Comparisons of Grades