Internal Use Only

Weakpoint

Internal Use Only

Overview

• Weakpoint calculation process • Cable weight in fluid • Maximum Safe Pull • Min and Max Pullout

Internal Use Only

Why do we need a Weakpoint?

A weak point is needed to enable us to free the cable from the Tool in the event of Tool getting stuck

Whether we actually free the cable at the weakpoint or not depends on other factors, but at all times a Wireline service company is expected to be able to free the wireline from the tool.

The weakpoint should never be broken unless both the Service company and the Customer are in agreement.

Breaking the weak point inadvertently can bring heavy penalties to the Service company

Not being able to break the weak point, when needed, can also bring heavy penalties to the service company

Internal Use Only

Properties of Cables Summary

Cable O.D” B.S Max Load lbs

Inner / Strength

Outer / Strength

Temp degF

Min Sheave Inch

Cond Resist. Ω/kft

Wt in air Lbs/kft

Stretch Ft/kft/klbs

Sp. Gravity

1K22PP 7/32 5200 2600 15/125 15/272 300 14 4 94 2.2 6.48

1K22PZ 7/32 5200 2600 15/125 15/272 500 14 4 97 2.2 6.67

1N22PZ 7/32 5200 2600 12/204 18/204 500 14 4 97 2.5 6.67

1N32PTZ 5/16 11000 5500 12/420 18/420 500 18 2.1 195 1.2 6.56

7J46RTZ 15/32 18000 9000 24/323 24/520 500 24 9.8 341 0.77 5.08

7H47RTZ 0.474 22000 11000 18/469 18/910 500 30 9.8 392 0.61 5.91

Cable identification used above is for Camesa cables

Internal Use Only

10,000’

5,000’ Tension on surface = 341 x 5 (kft) = 1705 lbs

Tension on surface = 3410 lbs

Vertical air well with 15/32” cable

Straight Hole No Sources of

Friction No MUD Tool wt? Cable stopped

Tension measured here

Weakpoint

Internal Use Only

10,000’

5,000’

Vertical well with mud and 15/32 cable

Straight Hole No Sources of Friction MUD of 11.32 ppg Cable stopped Specific gravity of cable =5.08

or 42.4 ppg Buoyancy Factor

= (42.4 – 11.32)/ 42.4 = 0.733 1 gm/cc = 8.3454 ppg

Tension measured here

Tension on Surface 341 x 5 (kft) x 0.733 = 1250 lbs

Tension on surface = 3410 x 0.733 = 2500 lbs

Weakpoint

( )

−

3454.8*3454.8*

SGMudwtSG

Internal Use Only

So far we have seen

When the Tool is stuck, the Tool weight is supported by whatever is holding the Tool and therefore Tool weight does NOT act on the Weakpoint

In order to put tension on the weakpoint we MUST pull over and above the Cable weight in Mud

At the same time we can never exceed 50% of the Minimum Breaking strength of cable

OR

Tension on Weak Point + Cable Weight in Mud < Half Breaking Strength of Cable

Therefore a simply formula for weakpoint can be:

Weak Point < Half Breaking Strength of Cable – Cable Weight in Mud

Internal Use Only

Process…

1. Determine the weight of the wireline in air and in water and min. breaking strength

2. Calculate the weight of wireline in BH fluid 3. Calculate the weight of wireline at TD 4. Calculate the ideal weak point 5. Select a weak point (WP) with max breaking strength less </=

calculated ideal WP

Internal Use Only

How to select a correct WeakPoint

The weakpoint has to be selected before our tools enter the well

To select Weakpoint we need:

1. Breaking Strength of the Logging Cable

2. Target Depth (T.D) of Well

3. Mud Density in well

Example 1:

Cable is 15/32”

T.D = 16,000 ft

Mud = 9 ppg

1 gm/cc = 8.3454 ppg

Steps

15/32 cable means Breaking strength = 18000 lbs, sp.gravity = 5.08, Wt.in air = 341

Convert T.D into Kft.

Apply formula CableCard 15/32 Camesa

WeakPoint < Half Breaking Strength of Cable – Cable Weight in Mud

Weak point < 9000 – (16 x 341 x BF) or 9000 – (5456 x BF) BF = (42.4 – 9)/42.4 = .7877

Weak point < 9000 – 4298 = 4702 lbs

Internal Use Only

How to select a correct WeakPoint

The weakpoint has to be selected before our tools enter the well

To select Weakpoint we need

1. Breaking Strength of the Logging Cable

2. Target Depth (T.D) of Well

3. Mud Density in well

Example 1

Cable is 15/32”

T.D = 16,000 ft

Mud = 9 ppg

Steps:

15/32 cable means Breaking strength = 18000 lbs, Wt.in air = 341, Wt in water = 274

Convert T.D into Kft.

Apply formula cable_cards.xls 15/32 Camesa

WeakPoint < Half Breaking Strength of Cable – Cable Weight in Mud

Weak point < 9000 – 16 x {341 – [(341-274) x 9/8.33]}

Weak point < 9000 – 4298 = 4702 lbs

Internal Use Only

It’s not over yet

Depending on the type of Cable Head being used, weak points can be selected from a set of fixed values.

We MUST select the highest value available that is lesser than our calculated weakpoint

In the last example we calculated 4702 lbs

Available weak points for DITS Cable Head are

1. 4000 lbs

2. 5000 lbs

3. 6000 lbs

4. 7000 lbs

Write down the weak point finally selected and installed on the Cable Head Record and inside the Logging Truck. In this example we have selected 4000 lbs.

(A Weak Point cannot be selected with a maximum breaking strength in excess of the ideal weak point value)

Internal Use Only

Some more examples Example 2

Cable is Slammer

T.D = 16,000 ft

Mud = 9 ppg

Example 3

Cable is 15/32”

T.D = 10,000 ft

Mud = 9 ppg

Example 4

Cable is 15/32”

T.D = 16,000 ft

Mud = 12 ppg

Weak point < 11000 – (16 x 392 x BF) or 11000 – (6272 x BF) < 11000 – (6272 x 0.81752) BF = (49.32 – 9)/49.32 < 5872 lbs

Weak point < 9000 – (10 x 341 x BF) or 9000 – (3410 x BF)

Weak point < 9000 – (16 x 341 x BF) or 9000 – (5456 x BF)

Alternate formula for finding weight of Cable in Fluid

WCBF = WCair – [(WCair – WCwater) X Mud wt in ppg / 8.33]

Internal Use Only

Weak points

Open Hole Cablehead

Internal Use Only

Weakpoint Hardware

Internal Use Only

Counting Conductors – see next slide!

• “ 10/08 Manual_D00000402_1.pdf Confidential & Proprietary Cable Strength and Safety Considerations 3-7

• The rope socket strength for a new monoconductor line is:

• 85% x Total number of outer armors x outer armor breaking strength

• The rope socket strength for a new Multi-conductor line is:

• For 7/16 and 15/32 cables: 85% x Number of outer armors x outer armor breaking strength

• For slammer cables (larger than .468) : 80% x Number of outer armors x outer armor breaking strength

• ONLY use Outer Armors in your calculation as per OEB 2010-042 -Cased Hole Cable Head, Mono-cable Head Rehead Standardization (Supersedes OEB 2006/065 and OEB 2008/104).

– *make comparison to chart

Internal Use Only

Mono-head Weak points

Mono-head weak points_REV3.xls

Internal Use Only

MSP Max Safe Pull

At Halliburton, Maximum Safe Pull (MSP) at any depth = Weight of Cable in Mud at that depth + 66% of Weak Point Rating installed in the Cable Head (when a weak point has a min and max rating, we use the MIN for MSP calculation as extra safety)

Maximum Safe Pull is NOT one value but a value that depends on the depth where the Tool is STUCK

Maximum Safe Pull can be calculated quickly for a vertical well.

For deviated wells it can only be estimated. Use Halliburton Weakpoint and Pull Calculator. WPCalc or Cerebus.

Note: Some other service companies use 75% of weak point as overpull. Please note we use 66%

Internal Use Only

Back to Example1

Example 1

Cable is 15/32”

T.D = 16,000 ft

Mud = 9 ppg

1 gm/cc = 8.3454 ppg

Calculated WP = 4702

Installed WP = 4000

What is the MSP at 16000ft?

Cable weight at 16000 ft + 66% of 4000

(16 x 341 x BF) + 2667 BF = 42.4 – 9 = .7877

4298 + 2667 = 6965 lbs 42.4

Surface Tension should NOT exceed 6965 lbs

What is the MSP at 12000ft?

Cable weight at 12000 ft + 66% of 4000

(12 x 341 x BF) + 2667 BF = 42.4 – 9 = .7877

3223 + 2667 = 5890 lbs 42.4

Surface Tension should NOT exceed 5890 lbs

Internal Use Only

Some more examples Example 2

Cable is Slammer

T.D = 16,000 ft

Mud = 9 ppg

Engineer decided to install 6000 lbs WP

Weak point < 11000 – (16 x 392 x BF) or 11000 – (6272 x BF) < 11000 – (6272 x 0.81752) BF = 49.32 – 9 < 5872 lbs

49.32

Calculate the MSP at 9000 ft

MSP at 9000 ft = Weight of Cable at 9000 ft + 66% of 6000

MSP = (9 x 392 x BF) + (4000)

MSP = 3528 x 0.81752 + 4000

MSP = 2884.2 + 4000

MSP = 6884 lbs

Internal Use Only

Cased Hole Example

Example 3

Cable is 7/32” 1K22

T.D = 10,000 ft

Mud = 11 ppg

Calculate Weak Point

Select Weak Point

Find MSP at 5000 ft

1 gm/cc = 8.3454 ppg

Cable O.D” B.S Max Load lbs

Inner / Strength

Outer / Strength

Wt in air /water Lbs/kft

Stretch Ft/kft/klbs

Sp. Gravity gm/cc

1K22PP 7/32 5200 2600 15/125 15/272 94 / 74.9

2.2 6.48

1K22PZ 7/32 5200 2600 15/125 15/272 97 / 77.8

2.2 6.67

Internal Use Only

Min and Max Pull out Tension

This is the tension that needs to be applied on the Weakpoint to break it free from the Cablehead.

Example

The # 6 weakpoint has a min of 5900 lbs and a max of 6600 lbs

Therefore in order to break a #6 weakpoint

Min tension on surface = Cable weight in mud at stuck depth + Min rating of WP

Max tension on surface = Cable weight in mud at stuck depth + Max rating of WP

Internal Use Only

Conclusion

• Weakpoint calculation process • Cable weight in fluid • Maximum Safe Pull • Min and Max Pull out tension

“The will to win means nothing without the will to prepare” Juma Ikangaa , Marathon Runner and Trainer

Internal Use Only

RWCH – Releasable Wireline Cable Head

• What is the benefit? – Consider the following…

• 2000lb toolstring • Cable 24k# MBS • 260lb/kft cable weight in mud • TD 18000ft, CSG 10000ft • What is the ideal weak point? Assuming the ideal weak point

is available – what max safe pull can you exert when the tool is stuck at TD? How about if you had an RWCH?

– Now consider the tool is stuck at 10000 ft what’s the max safe pull? How about if you had an RWCH?