investigating measured cement bond against theoretical ......obm type is predominant in 9 5/8”...

Copyright of Shell UK Ltd

Investigating Measured Cement

Bond Against Theoretical

Placement In The Brent Field

Diana Cristancho – Petrophysicist

Rob Lee – Head PP Solutions

Delta

Charlie

Bravo

Alpha

DEVEX

6th

May 2014


Definitions & Cautionary Note

Reserves: Our use of the term “reserves” in this presentation means SEC proved oil and gas reserves.

Resources: Our use of the term “resources” in this presentation includes quantities of oil and gas not yet classified as SEC proved oil and gas reserves. Resources are consistent

with the Society of Petroleum Engineers 2P and 2C definitions.

Organic: Our use of the term Organic includes SEC proved oil and gas reserves excluding changes resulting from acquisitions, divestments and year-average pricing impact.

Resources plays: our use of the term ‘resources plays’ refers to tight, shale and coal bed methane oil and gas acreage.

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sometimes used for convenience where references are made to Royal Dutch Shell plc and its subsidiaries in general. Likewise, the words “we”, “us” and “our” are also used to refer

to subsidiaries in general or to those who work for them. These expressions are also used where no useful purpose is served by identifying the particular company or companies.

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either a majority of the voting rights or the right to exercise a controlling influence. The companies in which Shell has significant influence but not control are referred to as “associated

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shareholding in Woodside Petroleum Ltd.) ownership interest held by Shell in a venture, partnership or company, after exclusion of all third-party interest.

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‘‘will’’, ‘‘seek’’, ‘‘target’’, ‘‘risks’’, ‘‘goals’’, ‘‘should’’ and similar terms and phrases. There are a number of factors that could affect the future operations of Royal Dutch Shell and could

cause those results to differ materially from those expressed in the forward-looking statements included in this presentation, including (without limitation): (a) price fluctuations in

crude oil and natural gas; (b) changes in demand for Shell’s products; (c) currency fluctuations; (d) drilling and production results; (e) reserves estimates; (f) loss of market share and

industry competition; (g) environmental and physical risks; (h) risks associated with the identification of suitable potential acquisition properties and targets, and successful

negotiation and completion of such transactions; (i) the risk of doing business in developing countries and countries subject to international sanctions; (j) legislative, fiscal and

regulatory developments including potential litigation and regulatory measures as a result of climate changes; (k) economic and financial market conditions in various countries and

regions; (l) political risks, including the risks of expropriation and renegotiation of the terms of contracts with governmental entities, delays or advancements in the approval of projects

and delays in the reimbursement for shared costs; and (m) changes in trading conditions. All forward-looking statements contained in this presentation are expressly qualified in their

entirety by the cautionary statements contained or referred to in this section. Readers should not place undue reliance on forward-looking statements. Additional factors that may

affect future results are contained in Royal Dutch Shell’s 20-F for the year ended 31 December, 2013 (available at www.shell.com/investor and www.sec.gov ). These factors also

should be considered by the reader. Each forward-looking statement speaks only as of the date of this presentation, 6 May, 2014. Neither Royal Dutch Shell nor any of its

subsidiaries undertake any obligation to publicly update or revise any forward-looking statement as a result of new information, future events or other information. In light of these

risks, results could differ materially from those stated, implied or inferred from the forward-looking statements contained in this presentation. There can be no assurance that dividend

payments will match or exceed those set out in this presentation in the future, or that they will be made at all.

We use certain terms in this presentation, such as discovery potential, that the United States Securities and Exchange Commission (SEC) guidelines strictly prohibit us from including

in filings with the SEC. U.S. Investors are urged to consider closely the disclosure in our Form 20-F, File No 1-32575, available on the SEC website www.sec.gov. You can also

obtain this form from the SEC by calling 1-800-SEC-0330.

2


Content

Overview of Brent abandonment

Project background and objectives

Bond Analysis

Squeezing shale

Cement

Top of Cement: Measured vs Theoretical

Observations and Conclusions

3


Brent Field Abandonment Philosophy

4

Three barriers

Barrier concept

Restore the cap rock. Top, mid and reservoir barriers.

Comply with Oil and Gas UK Guidelines for well suspension and abandonment.

Well integrity compliance: Acoustic and Ultrasonic logs to assess bond.


Background and Objectives

5

Had acquired 50 sets of NEW cement logs from abandoned wells

A consistent evaluation process throughout

Audit trail of log data and interpretations

Readily accessible well history records

About 100 wells were still to be abandoned on Brent. (Oct 2013)

Was there enough information to derive a prediction model?

Objective: Determine any critical relationships between the

environment and cementing process, and the resultant bond(s).

Aim: Assess any potential benefit to P&A planning, and/or

improving ‘Top of Cement’ estimates.


Initial Variable Review List

Variables

Casing/Hole Size

Mud Type

Mud Weight

Cement Type

Cement Weight

Maximum Deviation

CBL Amplitude & Bond Index

Drilling Hazards

TTOC

TOC

Cement Additives

Lead Volume

Tail Volume

Spacer Volume

Displacement Rate

Thickening time

Circulation Pressure

Casing centralisation

Well Type

Drilled date

Casing Weight/Type

Variables evaluated

Challenge to find

information

Not Included

6


Barriers and Bond

7

Good

Bond

Poor

Bond

Barriers

Logged

Success

Rate

Top Barrier (Utsira) 1 23 24 4%

Mid Barrier (Horda) 19 9 28 68%

Reservoir Barrier (Shetland) 14 7 21 67% CEMENT OR SQUEEZING SHALE?

Horda formation squeeze provides

barrier in 54% of all instances

(79% of ‘good bond’ occurrence)

For Shetland, 36% of ‘good bond’

occurrence could be due to squeeze

or combination with cement.

NO FURTHER ACTION

4

9

15

5

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Mid Barriers (Horda) Reservoir Barriers Shetland

Cement Squeezing shales

Good Bond Analysis


Squeezing shale as a barrier

Permanent well barrier should have the following properties;

1. Impermeable

2. Long term integrity

3. Non shrinking

4. Ductile (non brittle - can withstand mechanical loads/impact)

5. Resistance to different chemicals/substances

6. Wetting, to ensure bonding to steel

Oil and Gas UK Guidelines invoke the same requirements as Norsok D-010.

SEM micrograph, Upnor Formation, Huggett and Knox

■ High effective stress

■ Uncemented rock

■ High water/smectite content

8


Horda Squeezing Factors – Mud Type?

9

Whilst WBM yielded a 50% success rate

for all occurrences, this still represents 2

from 3 wells in this environment.

(88% of the ‘good’ wells)

OBM environment success, only 1 from 4

OBM

OBM 19%

50%

25%

WBM 75%

13 3/8" casing GOOD BOND

POOR BOND

OBM 28%

OBM 27%

WBM 27%

WBM 18%

9 5/8" casing

No significant statistical trend.

WBM


Cement Sheath Variables – Hole Size

10

Barriers Logged

Good Bond

Success Rate

13 3/8” casing (17 ½” bit size) 17 4 24%

9 5/8” casing (12 ¼” bit size) 21 9 43%

Theoretical

Stand-offs

17 1/2" & 13 3/8" 2.0625

12 1/4" & 9 5/8" 1.3125

0.06 bbl/ft

0.12 bbl/ft

Higher annular velocities (at same displacement rates)

would clearly be achieved in the 9 5/8” x 12¼” scenario.

Copyright of Shell UK Ltd 11

OBM type is predominant in 9 5/8”

‘good’ bond set. (43% success rate)

Whilst similar statistic exists for

WBM in 13 3/8” casing, the sample

set is a very small percentage of all

logged intervals.

Variables: Mud & Cement types

There was found to be no distinct union between these 2 variables.

GOOD BOND

Although Pozzo success stands out

for ‘good bond’ results, and it’s the

only cement type found for 13 3/8”

‘good’ bond results, the sample set is

a very small percentage of all logged

intervals.

GOOD BOND


Further Investigation?

Casing centralisation

Casing pressure variations

Stress variations in the formation

Spacer volume and well conditioning

Study in 1995 suggested cement displacement

rate as a prime factor in cement bond quality for

different liner sizes


VARIABLES

TTOC(high); assumes reported volumes, gauge hole, no losses.

TTOC(low); assumes hole is 10% over gauge.

TOC refers to top of 80% Bond Index here.

13

Acceptance criteria

• Cement provided good isolation from TOC to casing shoe

• TOC cement volumes assumes a gauge hole.

For comparison purposes

A 'performance’ factor was calculated

Top of Cement – Measured vs Theoretical


Tops of Cement – 13 3/8” Casing

14

The TOC was found deeper than TTOC(low) in 75% of the wells.


Performance Factor – 13 3/8” Casing

15


Performance Factor & TTOC – 13 3/8” Casing

16

The performance factor depth is still better than any theoretical in 75% of the wells.


Tops of Cement – 9 5/8” Casing

17

Well bonded pipe was found shallower than TTOC in half of the wells!

‘Mixed’ cement and formation profile.


Observations and Conclusions

18

Most significant correlations

Squeezing shale (Horda)

13 3/8” casing and WBM

Cement bond in 9 5/8” casing

OBM statistically more prevalent

Tops of cement (estimation)

Efficiency factor for 13 3/8” casing

General improvement over standard methods

Questions?

Thank you

investigating measured cement bond against theoretical ......obm type is predominant in 9 5/8”...

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