Well-specific risk assessment (WRA) for exploration well 35/10-5 Gabriel

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Well-specific risk assessment (WRA) for exploration well

35/10-5 Gabriel

EQUINOR ENERGY AS, avd Stavanger

Report No.: 2019-0829, Rev. 0 Document No.: 476380 Date: 2019-08-19

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Project name: WRA Gabriel exploration well DNV GL AS Veritasveien 1 1363 Høvik Norway

Tel: +47 67 57 99 00 NO 945 748 931 MVA Report title: Well-specific risk assessment (WRA) for exploration

well 35/10-5 Gabriel

Customer: EQUINOR ENERGY AS, avd Stavanger Forusbeen 50

4035 STAVANGER Norway

Customer contact: Linda-Mari Aasbø / Gisle Vassenden Date of issue: 2019-08-19

Project No.: 10163853

Organization unit: Environmental Risk and Preparedness, and Drilling

& Well

Report No.: 2019-0829, Rev. 0 Document No.: 476380

Delivery of this report is in accordance with Frame agreement 4600022577.

Objective:

Equinor is planning to drill 35/10-5 Gabriel exploration well, which is in the North Sea, in production licence [PL] 827 S prospect. This well-specific risk assessment is intended to provide a more well-specific basis for conducting the Environmental Risk Analysis.

Prepared by: Verified by: Approved by:

Rajesh Mistry

Principal Engineer Helene Østbøll

Principal Consultant Odd Willy Brude

Senior Principal Consultant

Copyright © DNV GL 2019. All rights reserved. Unless otherwise agreed in writing: (i) This publication or parts thereof may not be copied, reproduced or transmitted in any form, or by any means, whether digitally or otherwise; (ii) The content of this publication shall be kept confidential by the customer; (iii) No third party may rely on its contents; and (iv) DNV GL undertakes no duty of care toward any third party. Reference to part of this publication which may lead to misinterpretation is prohibited. DNV GL and the Horizon Graphic are trademarks of DNV GL AS.

DNV GL Distribution: Keywords:

☐ OPEN. Unrestricted distribution, internal and external. Well, Risk, Assessment, WRA, blowout, frequency, hydrocarbons, geology, operations, reservoir, exploration, drilling

☒ INTERNAL use only. Internal DNV GL document.

☐ CONFIDENTIAL. Distribution within DNV GL according to applicable contract.*

☐ SECRET. Authorized access only.

*Specify distribution:

Rev. No. Date Reason for Issue Prepared by Verified by Approved by

A 2019-08-09 First draft issued for comments. RAMIS CVTJ

0 2019-08-19 First issue RAMIS HELOS BRUDE

Digitally signed by Rajesh Mistry

Date: 2019.08.19 15:53:45 +02'00'

Østbøll, Helene

Digitally signed by Østbøll, Helene Date: 2019.08.19 15:58:55 +02'00'

Brude, Odd Willy

Digitally signed by Brude, Odd Willy Date: 2019.08.19 16:00:34 +02'00'

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1 EXECUTIVE SUMMARY

DNV GL facilitated a well-specific blowout risk assessment [WRA] review for the PL827 S Gabriel (35/10- 5) exploration well on July 9^th, 2019. Expertise was present from Equinor, Seadrill and DNV GL. The panel of experts represented the following disciplines: drilling, geology, reservoir, HSE, well design and construction.

WRA is a quantitative risk screening method to identify on a high level, the main risks for a potential blowout on a specific well. It addresses the main challenges related to reservoir and underground conditions, uncertainties, rig, well and operations.

The output from a WRA is a well-specific likelihood for blowout. Typically, the results can be used in the environmental risk assessment and as input for well planning and detailed risk assessments.

It is expected that the reservoir discovery being oil filled, with the top reservoir being at 1760 m TVD MSL.

Well Risk Assessment tool revision 2019 is utilised for this assessment, and the outcome of the WRA concluded that the blowout likelihood for the PL827 S Gabriel (35/10-5) exploration well is 6.44 10 . ⋅ ⁻⁵ This is approximately 56% lower than the blowout frequency for a generic exploration well (1.14 10 ). ⋅ ⁻⁴ Some of the key factors contributing to the frequency reduction are:

- Only one reservoir target is identified.

- New and re-processed seismic data is used for the seismic interpretation.

- The Gabriel well path is not identified to traverse any faults throughout the interpreted interval.

- The BOP and wellhead are rated to 1034 bar, i.e. with good margins from the maximum reservoir pressure of 186 bar.

- The well is vertical.

During the workshop the following issues were highlighted as risk increasing factors:

- Unconsolidated sand can be expected, but will most likely not be the case based on the experiences while drilling the nearby Stålull well.

- The risk of encountering shallow water flow is considered to be low but cannot be excluded at the location.

- The expected absolute permeability is expected to be as high as 1111 mD (effective 911 mD).

- Up to 6 wireline runs in discovery case.

Additional information can be found in Appendix C.

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2 INTRODUCTION

A well risk assessment [WRA] for the PL827 S Gabriel (35/10-5) exploration well took place on July 9th, 2019.

The WRA was facilitated and documented by DNV GL, with participating experts from Equinor and Seadrill. The outcome from the WRA has been processed by DNV GL to yield a well specific likelihood for blowout for the drilling operation on PL827 S Gabriel (35/10-5) exploration well.

2.1 Background

PL827 S Gabriel (35/10-5) exploration well is located in production licence [PL] 827 S, about 41 km northeast of Kvitebjørn field in the North Sea [1]. The water depth at location is approximately 368 m.

Figure 2-1: Location of PL827 S [1].

The drilling operation is planned to be performed by West Hercules, which is a dynamic-positioned class 3 semi-submersible built in 2008. The rig is designed to operate in harsh environments and at water depths of up to 3000 m, and has a 15k psi BOP with 5 rams and 2 annular (annular is rated to 10k psi).

The Gabriel exploration well is planned to be drilled into the Paleogene/Intra Balder and Sele sandstone formations, with maximum planned TD at 1968 mTVD RKB in the Lista formation independent of reservoir outcome. The probability of discovery is stated to be 33% [3].

Nine key relevant reference wells are identified, with the closest being 35/10-4 A and S (Stålull and Gnomoria), located 4,4 km Southeast of the Gabriel well [3]. The Stålull well drilled through the same sands and no challenges were experienced while drilling the sands. Also, the caliper logs from Stålull suggests the sands not being unconsolidated.

PL827 S

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2.2 Objective

The main objectives of the WRA were:

− Identify on a high level, the main challenges (risks) related to reservoir and underground condition, uncertainties, rig, well and operational aspects.

− Establish a well-specific blowout likelihood in connection with the planned drilling operation of PL827 S Gabriel (35/10-5) exploration well.

2.3 Methodology

The methodology addresses the core parameters influencing environmental and safety risks related to blowouts; likelihood, the potential hydrocarbon flow rates, and duration. Only the assessment of the likelihood is covered in this report. A more detailed description of the method can be found in SPE- 157319-PP – Well-specific Blowout Risk Assessment [4].

2.3.1 Generic blowout likelihoods from SINTEF Offshore Blowout Database 2018 [2]

The WRA has used the Lloyd's Blowout and well release frequencies based on SINTEF Offshore blowout database 2018 [2] report as a basis for establishing the well specific blowout frequency.

The estimated blowout and well release frequencies found in the report are mainly based on data from the North Sea (Norwegian, British and Dutch sector) and the United States Gulf of Mexico Outer Continental Shelf. In addition, Canada East Continental Shelf is included for shallow gas incidents.

According to the report, ref [2]:

For this edition of the report, the methodology based on the weighted conjugate distribution, adopted in 2014, is followed. Rather than focusing only on the data from the last 20 years, as has been done before 2014, the full data set for the time period 01.01.80 - 31.12.16 has been used, and is weighted to give more emphasis on recent data.

Furthermore, the report includes only hydrocarbon releases in the frequency calculations, and underground blowout with no release to the sea or platform is excluded.

Table 2-1 gives an overview of the generic blowout frequencies used as basis for assessing the likelihood for blowout for the drilling operation on PL827 S (35/10-5) exploration well.

Further description of the assessment is given in section 2.3.5.

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Table 2-1: Generic blowout frequencies from SINTEF Offshore Blowout Database 2018 [2]

Well Type Average Gas Oil Unit

Exploration well 1.32E-04 1.47E-04 1.14E-04 Per well

Exploration well (HPHT) 8.19E-04 9.12E-04 7.06E-04 Per well

Wildcat well 1.36E-04 1.51E-04 1.17E-04 Per well

Wildcat well (HPHT) 8.41E-04 9.36E-04 7.24E-04 Per well

Development well 3.56E-05 3.97E-05 3.07E-05 Per well

Development well (HPHT) 2.21E-04 2.46E-04 1.90E-04 Per well

2.3.2 Well-specific blowout likelihood

The well specific blowout likelihood is based on assessing the specific characteristics of the well’s surrounding environment, and the operation to drill the well. A list of risk factors is reviewed by a multidisciplinary team familiar with the exploration well and drilling rig, and risk factors are ranked according to their potential. The risk factors are weighted and a well and operation specific likelihood score is calculated. This score is compared to a benchmark, and the blowout likelihood is deduced based on the benchmark frequencies.

2.3.3 Risk factors

The likelihood of losing well barriers, followed by a blowout, is influenced by several risks. The WRA organise the main risk factors into four categories:

- Geology - Uncertainties - Rig, riser and well - Operational aspects

Risk factors related to reservoir and underground are captured within the geology and uncertainty categories, while risk factors related to operational aspects are captured within the rig, riser and well and operational aspect categories. The risk factors are developed based on historical data, scientific publications and on experience, and are further given an impact factor depending on its criticality.

The different categories have different influence on the blowout frequency; therefore, categories are given contribution percentages. The weighting is based on typical factors that have historically been causes for blowout. Studying blowout records from SINTEF, it has been assessed that geology risk factors contribute to 35% of the blowouts. The contribution from uncertainties is circa 30%, operational aspects (e.g. tripping) circa 10%. Other contributors have been categorised under “Rig, Riser and Well”

(25%).

Table 2-2 lists each of the categories, including the weight the categories have been given and the risk factors located within the categories.

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Table 2-2: Categories and risk factors discussed during the WRA workshop.

Category (weight %) Risk factor

Geology (35%)

Number of reservoirs/targets Challenging drilling formations Faults

Pressure margin

Pore pressure in the reservoir(s) Over pressure

Bore hole stability Permeability Net pay

Uncertainties (30%)

Seismic data Offset wells

Top reservoir depth uncertainty Pressure uncertainty

Rig, riser and well (25%)

Drilling crew experience Rig and well control equipment Riser

BOP Wellhead

Drilling water depth

Operational aspects (10%)

Trips related to well design and coring after first reservoir is hit Well design - shape

Logging runs after first reservoir is hit

2.3.4 Risk review

The risk factors listed in Table 2-2 are reviewed and ranked from 1 to 9 during a workshop with rig, well construction, geologists, reservoir and HSE representatives for the specific well. The risk ranking is based on available information on reservoir and underground conditions, the well design, the project, the rig and on the workshop participants’ experience and best judgment. As an outcome of the workshop, the well is given a specific weighted well score from 1 (low risk) to 9 (high risk). Figure 2-3 illustrates the process for determining the well specific score.

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Risk factor score Score 1-9

.

Risk factor score ..

Reservior and underground conditions

Uncertainties

Rig, riser and well

Operational aspects Impact

35%

Impact 30%

Impact 25 %

Impact 10 %

Well average weigted score

1-9 Weight

Weight

Figure 2-2: The process for determining the well specific score.

2.3.5 Assessing the likelihood for blowout

The outcome of the risk review is a specific well score, which is further interpolated between pre-defined well scores for typical wells and their corresponding historical blowout frequency, yielding a specific likelihood for blowout for the well of interest. The historical blowout frequencies are taken from the Lloyd’s report which estimates generic blowout frequencies based on data from the SINTEF offshore blowout database [2].

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3 RESULTS

This chapter summarises the main aspects from the WRA workshop and the corresponding blowout likelihood for an oil filled PL827 S Gabriel (35/10-5) exploration well. A list of the workshop participants is provided in Appendix B, and the WRA record sheet is provided in Appendix C.

3.1 Risk assessment

During the WRA most of the risk factors were given a low (score 1-3) to medium (score 4-6) risk value for the PL827 S Gabriel (35/10-5) exploration well, except for the following:

- Permeability (score 7)

The expected absolute permeability in the reservoir is 1111 mD, which is considered to be high. During the workshop, DNV GL was informed that this is a difficult parameter to evaluate and there is high uncertainty related to this value. As the permeability is > 1000 mD, a score of 7 was given.

Details from the WRA workshop are presented in Appendix C.

3.2 Blowout likelihood

An oil filled PL827 S Gabriel (35/10-5) exploration well was in the workshop assessed to a specific score of 2,68, on a scale ranging from 1 to 9. This score is further interpolated between pre-defined well scores for typical wells and their corresponding historical blowout frequency, yielding the following specific likelihood for oil blowout for the Gabriel exploration well: 6.44 10 . A comparison of the PL827 ⋅ ⁻⁵ S Gabriel (35/10-5) exploration well risk level and the generic risk level for different well types can be seen in Appendix E.

The likelihood for a blowout is about 56% lower than of a typical exploration well, 1.14 10 . The ⋅ ⁻⁴ comparison to generic blowout likelihood for this well is as follows:

- 2.10 times the frequency of a development well (3.07 10 per well). ⋅ ⁻⁵ - 0.56 times the frequency of an exploration well (1.14 10 per well). ⋅ ⁻⁴ - 0.55 times the frequency of a wildcat well (1.17 10 per well). ⋅ ⁻⁴

The estimated blowout likelihood for the PL827 S Gabriel (35/10-5) exploration well is lower than that of an exploration well or a wildcat well. This is due to more comprehensive knowledge of the area combined with having good mitigating actions in place to handle the potential geological and drilling hazards.

3.2.1 Effect of individual risk factor

The effect each risk factor has on the well specific score is shown in Figure 3-1, while the contribution the risk factors have in their respective category can be seen in Figure 3-2, Figure 3-3, Figure 3-4 and Figure 3-5. The contribution is based on the score given in the workshop, the impact factor and the weight of the individual category.

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Figure 3-1: Contribution to the well specific score for each risk factor.

Figure 3-2: The contribution to the geology specific score for each risk factor within the geology category.

0%10%

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Offset wells Pressure margin Permeability Top reservoir depth… Pressure uncertainty Challenging drilling formations Net pay Over pressure Trips related to design and… Drilling crew experience Rig and well control… Riser BOP Wellhead Faults Pore pressure in the… Logging runs after first… Bore hole stability Well design - shape Seismic data Drilling water depth Number of reservoirs/targets

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Contribution to the well specific score for each risk factor

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Contribution to the geology category

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Figure 3-3: The contribution to the uncertainties specific score for each risk factor within the uncertainties category.

Figure 3-4: The contribution to the rig, riser and well specific score for each risk factor within the rig, riser and well category.

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Offset wells Top reservoir depth

uncertainty Pressure

uncertainty Seismic data

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Contribution to the uncertainties category

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Contribution to the rig, riser and

well category

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Figure 3-5: The contribution to operational aspects specific score for each risk factor within the operational aspect’s category.

3.3 Limitations

The results of the WRA on the PL827 S Gabriel (35/10-5) exploration well are based on the input data and information provided by the participants before and during the workshop. The information provided by Equinor's specialists was discussed during the workshop; however, no other means of verification have been carried out by DNV GL.

WRA is a high-level risk screening method and hence no detailed risk assessment for the actual operation has been done. It is the responsibility of the operator to manage the risk during the planning and drilling of the well.

0%

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45%

Trips related to design and coring after first

reservoir is hit

Logging runs after first

reservoir is hit Well design - shape

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Contribution to the operational aspect

4 REFERENCES

[1] NPD, “NPD Factpages” [Online]. Available: http://factpages.npd.no

[2] Lloyd’s Register Consulting, “Blowout and well release frequencies based on SINTEF offshore blowout database 2018,” Report number 19101001-8/2019/R3, 08.04.2019

[3] NO 35-10-5 Gabriel exploration well - Well Risk Assessment 09.07.2019 - Background info, Equinor, 09.07.2019

[4] SPE-157319-PP, Well-specific Blowout Risk Assessment, SPE International 2012. Paper presenting method for Well Risk Assessment.

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APPENDIX A Abbreviations

The abbreviations used in this report include:

Abbreviation Full meaning

BHA Bottom hole assembly

BOP Blow out preventer

HSE Health, safety and environment

mD Millidarcy

NPD Norwegian Petroleum Directorate

PL Production licence

TD Total Depth

TVD True Vertical Depth

WRA Well risk assessment

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APPENDIX B

List of workshop participants

Name Company Role/Position

Linda-Mari Aasbø Equinor Senior Environmental Advisor Kristin Müller Thomassen Equinor Environmental Advisor

Simen Jøsang Nilsen Equinor SSU

Mark Van Schaack Equinor Geophysicist

Daniel Finken Equinor Operation geologist

Osazee J. Igbineweka Equinor Petroleum engineer Tolleif Grønås Equinor Petroleum engineer Kristoffer Alfthan Equinor Lead drilling engineer Per Walter Ulvedal Equinor Petrophysicist

Martin Stalsberg Equinor Project leader Exploration Svein Arne Almeland Seadrill Planning

Øyvind Fredriksen Seadrill Toolpusher

Rajesh Mistry DNV GL Facilitator and Scribe, Drilling and Well Helene Østbøll DNV GL Environmental Risk Management

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APPENDIX C

Well Risk Assessment Workshop log sheet

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Client Date

Equinor 09.07.2019

Risk factor Impact factor Criteria Score Justification/reasoning Weighted

score Number of

reservoirs/targets 2 1-3: 1 target

4-6: 2 to 3 targets

7-9: ≥ 4 targets 1 One reservoir target. No apparent secondary prospectivity near proposed well location.

The target and area is expected to be well defined. 2

Challenging drilling

formations 2

1-3: normal consolidated sandstones, limestone 4-6: normal consolidated siltstones and shale

7-9: basement, quartzite, unconsolidated formations, highly fractured formations, thick

evaporate layers

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Utsira: Potential weak sand. Problems RIH/POOH, run casing, overpressure, shallow- water cannot be excluded.

Balder: Potential for first reservoir sand interval, loose quartz, and poorly consolidated. Washout, problems RIH/POOH.

Sula Member: Reservoir sandstone, loose quartz, poorly consolidated. High porosity/permeability, differential sticking, swab/surge, washout.

Similar wells have been drilled in the area. Have had a case where shallow-water flow was experienced in Utsira. Unconsolidated sand can be expected, but will most likely not be the case based on the experiences while drilling the nearby Stålull well.

Stålull well drilled through the same sands. Not experienced challenges while drilling the sand. Caliper logs from Stålull suggests the sands not being unconsolidated.

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Faults 3 1-3: 1 fault

4-6: 2-3 faults

7-9: >4 faults 2

The Gabriel well path is not identified to traverse any faults throughout the interpreted interval.

The well is located outside the spots with identified faults. However, cannot rule out sub-seismic events, but major faults can be ruled out. Differential compaction

observed earlier.

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Pressure margin 3 1-5: >0.12 s.g

6-9: <0.12 s.g 5

Highest expected pore pressure ~1.27 SG Fracture pressure at highest pore pressure: ~1.53 SG (0,26 SG margin)

Shallow-water cannot be excluded in Utsira.

Pressure margins (pore pressure vs mud weight):

- 17 1/2" section - Max PP 1,02 SG, MW - 1,02 sg SW; 0 sg margin (Utsira fm) - 12 1/4" section - Max PP 1,27 sg (in clay), MW 1,3-1,4 sg; 0,03 - 0,13 sg margin - 8 1/2" section - Max PP 1,27 sg (in clay), MW 1,3-1,4 sg; 0,03 - 0,13 sg margin Reservoir pressure at top reservoir is estimated to 186 bar (1,05 g/cc). Margin in

reservoir is viewed as good, and sufficient in the clay.

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Pore pressure in the

reservoir(s) 3 1-3: <340 Bar

4-6: 340<690 Bar

7-9: >690 Bar 2 Expected maximum reservoir pressure: 186 bar 6

Over pressure 3

1-3: good data on pressure profiles and no overpressures expected 4-6: good data on pressure profiles and few

overpressures expected 7-9: poor data on pressure profiles, or several

overpressures expected

3

Balder: Overpressure identified as a hazard. Shallow-water cannot be excluded.

Pressure measurements exists in the Balder formation (taken in Stålull well).

Correlation between Stålull and Gabriel well is good. Seismic marks suggest the wells to be similar.

Closest offset well to Gabriel have similar pressure profile. No overpressure expected.

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Bore hole stability 2 1-3: High borehole stability x low uncertainty 4-6: High borehole stability x high uncertainty

7-9: Low borehole stability x higher uncertainty 2 Have good sonic and density data that is used to generate the collapse curve. LOT data is available in the area. Pressure points in Utsira also confirms this. I.e. good

offset data. 4

Permeability 2

Oil reservoir:

1-3: < 250 mD 4-6: 250 mD < 1000 mD

7-9: > 1000 mD Gas reservoir:

1-3: < 50 mD 4-6: 50 mD < 100 mD

7-9: > 100 mD

7 Average absolute permeability 1111 mD (effective 911 mD) Viewed as a difficult parameter to evaluate, i.e. high uncertainty.

1000 mD used for blowout and kill simulations.

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Net pay 3 1-3: < 20 m

4-6: 20 m < 50 m

7-9: > 50 m 4 Total formation thickness 51,5 m TVT

Net pay is 23,6 m, which is based on the expected OWC. 12 3,5

score Seismic data 1 1-3: new or re-processed 3D seismic

4-6: re-processed 2D seismic

7-9: 2D seismic < 7 years 1 Good seismic signal. New seismic data and re-processed. Good confidence in the

seismic data. 1

Offset wells 3

1-3: More than one offset well from the same geological structure (very similar

characteristics), 4-6: One offset well from the same geological

structure (very similar characteristics), 7-9: No offset well available

3

- 9 offset wells, with the closest well (35/10-4 A and S) appx. 4,4 km southeast of Gabriel.

- The key reference wells for the pore pressure prognosis is the 35/10-1 (7,7 km southwest), 35/10-2, 35/10-3, 35/10-4 S (4,4 km southeast) and 35/11-18 A wells.

35/10-1 and 35/10-4 are more relevant for pressure prognosis. There are many reference wells in the area. These are considered as reference wells used for experiences. However, the closest wells are picked as the most relevant wells.

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Top reservoir depth

uncertainty 3 1-3: Very few uncertainties

4-6: Medium uncertainties

7-9: High uncertainties 2 Reservoir, uncertainty +- 22-23 m TVD. Good control of depth (e.g. top Balder).

Markers while drilling the well will reduce the uncertainty. 6

Pressure uncertainty 2

1-3: Low uncertainties (several offset wells, good seismic data) 4-6: Medium uncertainties (only one offset

well, average seismic data) 7-9: High uncertainties (few data available)

3 2 of the most relevant wells is used for pressure prognosis. Still some uncertainty. 6

2,4

score

Drilling crew

experience 3

1-3: Crew is used to drilling similar wells in the same context (geology, rig, external conditions) 4-6: Crew has already drilled wells with similarities, but there are new factors (geology,

rig, external conditions) 7-9: Crew has never drilled similar wells or the

context is new (geology, rig, external conditions)

2

Rig name: West Hercules (DP class 3 semi-sub) Rig has drilled similar exploration wells, and rig crew has obtained good experience in

drilling similar wells. Gladsheim and EOS wells will be drilled before Gabriel.

Same crew will be used.

6

Rig and well control

equipment 3

1-3: Rig able to sufficiently kill well (mud pumps, kill fluids etc.)

4-6: Uncertain if rig is able to kill well 7-9: Rig unable to kill well

2

Highest expected reservoir pressure is 186 bar (1,05 sg).

Blowout and kill simulations show the well can be killed with one relief well. Will have kill fluid available, and rig will be able to kill the well. Gabriel well is viewed as

one of the "easiest" wells to be drilled. Well design is known and rig crew are experienced. Frequent well control drills are performed.

6

Riser 3 Riser margin, pressure rating, fatigue of riser 2

Cameron LK 75 ft Length 21” OD, 4” ID Boost Line.

With the stated reservoir pressure (186 bar, 1,05 sg) and TD at maximum 1968 mMD, rig will be able to drill with riser margin. Plan is to drill with 1,4 sg WBM. However, if

required, an evaluation will be made to drill the well with OBM.

6

BOP 3 Size, number of RAM, type of control system 2 West Hercules has a 15 000 psi (1034 bar) 18-3/4" BOP-stack.

15k psi BOP, 5 rams (rams are 15k psi) and 2 annulars (annulars are 10k psi). MUX

control system. 6

Wellhead 3 Pressure rating 2 15k psi (1034 bar). Wellhead fatigue analysis may be performed. 6

Drilling water depth 1 1-3: Shallow to medium water (< 400 m) 4-6: Deepwater (400 < 1500 m)

7-9: Ultra deep water (> 1500 m) 2 Water depth is 367,5 m MSL (RKB - MSL: 31 m). Troll field Metocean data is available.

Rig has the possibility to drill on DP. Decision on using DP/anchors will be evaluated

at a later stage. 2

2,0

score Trips related to

design and coring after first reservoir

is hit

2 1-3: Low number of trips expected (<4) 4-6: Average number of trips expected (4<8)

7-9: High number of trips expected (>8) 3

Dry case: No coring planned.

Discovery case (33% probability): 1 conventional coring run (54 m) Unexpected trips may be possible, but still below 4 coring runs.

No BHA change is planned for.

6

Well design - shape 3 1-3: Vertical well

4-6: Deviated

7-9: Sinus 1 Well path is planned vertical. No geological sidetrack is planned. Highly confident that

the well will be close to vertical at TD. 3

PL827 S, 35/10-5 (Gabriel)

Project

Rig, riser and well (1 to 9)

Rig, riser and well

Operational aspects Geology

Uncertainties score (1 to 9) Uncertainties

Pressures and stability

Reservoir

Geology score (1 to 9)

Uncertainties

Local geology

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APPENDIX D

Additional Background information

This appendix contains the following background information provided by Equinor:

• Geological prognosis

• Prognosed Pore pressure, fracture, overburden gradients

• Well schematics

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Figure D- 2: Prognosed Pore pressure, fracture, overburden gradients

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Figure D- 3: Well schematics

36"

13 3/8"

9 5/8"

TD

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APPENDIX E

Comparison of the Gabriel (35/10-5) exploration well risk level and the generic risk level for different well types.

The outcome of the WRA concluded that the blowout likelihood for the Gabriel (35/10-5) exploration well is in the order of 6.44 ∙10^-5. This is approximately 56 % lower than the blowout frequency for a generic exploration well and is illustrated in the Figure below.

Comparison of the Gabriel (35/10-5) exploration well risk level and the generic risk level for different well types (logarithmic scale for frequency.

1,0E-05 1,0E-04 1,0E-03 1,0E-02

1 2 3 4 5 6 7 8 9

Blowout frequency (per well)

Well risk level

Exploration well HPHT Exploration well Wildcat well Wildcat well (HPHT) PL827 S, 35/10-5 (Gabriel) Development well HPHT Development well

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Well-specific risk assessment (WRA) for exploration well 35/10-5 Gabriel