©2012 TAM International, Inc.

COUNTING THE COST

Enhanced Well Construction Techniques to Reduce Well Abandonment Costs

Ian Bayfield, TAM International

5th European Well Abandonment Seminar

21st April 2015

The objective of this presentation is to highlight challenges that can be experienced during well construction and illustrate solutions that have be used to enhance cementing operations, assist in achieving zonal isolation and improve annular casing integrity for the life of the well.

Overview of Gas Migration revealed as Sustained Casing Pressure (SCP) and

Cementing Best Practices.

Solutions to mitigate against SCP and enhance cementing operations

during well construction with some case histories.

Consequences of incomplete zonal isolation.

Conclusions.

Presentation Agenda

2

Poor zonal isolation resulting in Gas Migration and revealed as SCP can occur at anytime during the life cycle of the well. The source of Gas Migration is normally classified into one of two categories, namely:

1. Primary or short term gas migration. Can occur when the cement is in transition state from a liquid

to a solid.

2. Secondary or long term gas migration Can occur when the cement has cured and developed compressive

strength and fracturing or de-bonding of the cement occurs.

Gas Migration

3

Cementing Best Practices

4

The main objective of cementing is to provide complete & long term zonal isolation behind the casing.

Cementing best practices can be compromised by:

Poor hole & mud conditioning.

Inadequate mud displacement leading to contamination of slurry, channeling and de-bonding allowing annular flow.

Inadequate centralization.

Irregular bore-hole, weak & depleted zones, or washouts resulting in low cement height.

Gas or fluid ingress during the cement hydration process.

Cementing Challenges

5

Primary gas migration – can be caused by:

Inadequate mud displacement leading to contamination of slurry, channeling and debonding allowing annular flow.

Cementing Challenges

6

Primary gas migration – can be caused by:

Cement column’s inability to maintain an overbalance pressure due to static gel strength and bulk volume loss, which can allow gas to enter the slurry and percolate up hole creating flow channels.

Mud Channel

Gas Channel

Cementing challenges

7

Secondary gas migration - can be caused by:

Micro annulus fractures or cement debonding caused by pressure and temperature cycling or formation shifts creating flow paths for gas migration.

5-1/2” x 7-5/8” sheath failure at 4,500 psi (31 MPa)

There have been significant advancements in cement slurry design properties to help resist gas migration and optimize the mechanical capabilities of the cured cement.

However…… In certain scenarios the cementing operation can be enhanced by including an inflatable annular barrier (CAP - Casing Annulus Packer) to give zonal isolation during the critical cement hydration period. This should absolutely NOT be considered as a replacement for cement but as a complimentary technology. If required the cementing operation can be performed in two discreet stages using a cementing collar or Port Collar.

The cementing operation may also be enhanced by the inclusion of a Swellable Packer positioned within the cement slurry or above top of cement.

Solutions to mitigate against SCP and enhance cementing operations during well construction

8

9

Plug Bump

Hydrostatic Decline

Static Conditions

NO fluid loss

NO gas influx

Inflate CAP

CAP

Gas Zone

Pressure Gauge

Pre

ssu

re

Time

Mu

d H

ydro

stat

ic

Cir

cula

tin

g

Ce

me

nt

abo

ve

Gau

ge

Possible Gas Flow

Static BHP

Prevention of Gas Migration with Casing Annulus Packer

Possible Gas Flow

Case History 1 – Elimination of Primary Gas Migration

10

Location: Onshore USA (Marcellus Shale).

Challenge: Sustained casing pressure (SCP)

due to shallow gas migration was observed on over 60% of a major operator’s wells drilled in the Marcellus Shale.

Solution: A modified drilling program utilized

9-5/8” CAPs to isolate the annulus above known gas bearing zones preventing future occurrences of SCP.

Value Added: Including a reliable, cost-

effective mechanical barrier in the cementing operations prevented future cases of SCP in the next 40+ wells.

11

Location: Azerbaijan.

Challenge: Operator sought a solution to shallow gas

migration and brine flows that had plagued most of their installations.

Solution: CAPs and PCs installed on the 20” casing

strings were set inside the conductor in order to achieve immediate isolation as well as a successful stage cement job with returns to surface.

Value Added: Over 60 wells have been completed

using this method on 20” strings with no gas migration issues, enabling field development.

Case History 2 – Elimination of Primary Gas Migration

12

Case History 2 – Casing Annulus Packer & Cementing Port Collar

13

Location: U.K. North Sea.

Challenge: SCP experienced on the first 3 wells of a

newly constructed unmanned platform.

Solution: 9-5/8” CAP and MTM Cementing Port Collar

positioned above gas-bearing zone in the 13-1/2” open hole utilized to perform the North Sea’s first successful two-stage cementing of production casing.

Value Added: By eliminating SCP we have improved

safety, increased asset value and reduced the complexity and cost of future well abandonment.

Case History 3 – Elimination of Primary Gas Migration

14

Case History 3 – Casing Annulus Packer & MTM Cementing Port Collar

15

Case History 3 – Casing Annulus Packer & MTM Cementing Port Collar

The cementing operation may also be enhanced by the inclusion of a Swellable Packer positioned within the cement slurry or above top of cement to guard against secondary gas migration. There are two ways the swell packer maybe be positioned within the casing string:

Full Bore Swellable Packer – The packer is designed with maximum possible elastomer O.D. to seal in the open hole or in previous casing string above the theoretical T.O.C.

Under-Sized Swellable Packer – The packer is designed with a reduced O.D. to seal against any potential micro-annulus formed within the cement around the elastomer O.D.

Solutions to enhance the cementing operation and prevent Secondary Gas Migration?

16

17

Applications…Full-bore Swellable Packer

• Redundant barrier above TOC – Packer sized to minimize impact on ECDs while still incorporating enough

rubber volume to seal annulus.

– Can be run in previous casing shoe or open hole depending on application.

18

Applications…Under-sized Swellable Packer

• In the event of channeling or micro annulus fractures, the Swellable Packer will swell and seal the void when exposed to the well activation fluid (water-based or oil-based)

Viscous/Immovable Mud Creates Channeling

Swellable Packer Swells and Seals Annulus

Preventing Channeling

19

Applications…Under-sized Swellable Packer

20

Case History 1 – Elimination of Secondary Gas Migration

• Location: Deepwater West Africa.

• Challenge: An operator sought a dependable, cost effective means of ensuring wellbore integrity in critical, deep-water West African wells.

Solution: Two 9-5/8” Swellable Packers were installed. The upper packer was installed above the T.O.C. and the lower packer was placed in the cement. The packer above the T.O.C. was larger O.D. to swell and seal inside the 13-3/8” casing and provide redundancy for the Liner Top Packer. The packer in the cement was a reduced O.D. to seal off any potential micro-annulus and prevent hydrocarbon flow.

• Value Added: Incorporating Swellable Packers into their cementing programs ensured the operator achieved reliable long term zonal isolation and redundancy for the Liner Top Packer.

Consequences of Poor Zonal Isolation and / or Gas Migration

21

Potential increased level of cost and degree of difficulty during well abandonment (Section Milling of Casing, Under-reaming Open Hole). See example illustration on next slide.

Well integrity challenges (SCP) for the life cycle of the well.

Potential HSE & legislative considerations.

Potential exposure to costly & timely remedial intervention to try to cure the problem.

Possibility of decreased productivity & profitability (e.g. water production, cross-flow….).

P&A - Section Milling / Under Reaming / Cementing

22

Section milling may be required due to SCP caused by inadequate zonal isolation when performing primary cementing during well construction.

Section mill 9-5/8” production casing and under ream O.H. back to virgin formation.

Drill pipe deployed 7-3/8” inflatable bridge plug run through production casing, set inside the under reamed O.H section.

Inflatable Bridge Plug acts as a base for the abandonment cement plug but more importantly prevents any gas migration from compromising the cement plug.

The open hole inflatable bridge plug and cementing operation is performed in a single run.

Section Milling & U/Reaming can be time consuming and costly. Depending on complexity of the operation – 5, 10, 15 days rig time?

Conclusions

23

When planning a new well it is prudent to recognize and understand the mechanisms which can cause gas migration and make best efforts to mitigate against them.

Selecting the appropriate cement slurry design in combination with best drilling and cementing practices, will also give greater probability of achieving zonal isolation and preventing gas migration. Many wells will not require any additional zonal isolation other than cement.

When appropriate, utilization of an inflatable annular barrier (and possibly stage cementing techniques) will greatly improve the probability of eliminating primary gas migration during well construction. Used correctly, this technology will enhance cementing operations.

Utilizing the correctly designed swellable packer can improve the probability of eliminating secondary gas migration.

Well abandonment can be simplified and performed in a more timely and cost effective manner if zonal isolation is achieved during well construction. A modest investment during well construction could prove to be a prudent investment throughout the life cycle of the well.

End of Presentation

24

Question - Would you do things differently 2nd time around?