Exploration well

7/26/2019 Exploration well

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Case study: Byrkje, PL607

Jannecke A. Moe

Advisor Environment

EXPERIENCE FROM PLANNING AN EXPLORATION DRILLING,INVESTIGATION AND SPONGE RISK ASSESSMENT

WORKSHOP ON SEABED HABITATS OF ENVIRONMENTAL CONCERN 2013

OSLO 17-18 OCTOBER



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INTRODUCTION: WELL AND CONDITIONS

Byrkje (PL607) is located about220 km from shore in the BarentsSea

Soft bottom sponges were foundmostly in in scattered densities Mainly Geodia spp.

An area of high density sponges identifiedabout 250-280 m from well

No corals or red listed speciesidentified

Water depth: 260 m

Rig: Transocean Barents

No anchors (Dynamic Positioning)

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EXPLORATION DRILLING: INVESTIGATIONS AND TIME PLAN

Prior to drilling

1. Rig contract / consortium agreements 1,5 – 3 years

2. Early phase environmental evaluation 15 months

3. Site- and baseline survey including habitat investigation 12 months

4. Particle distribution simulation (DREAM) 9 months

5. Environment risk assessment 6 months

6. Evaluate possible and suitable risk reduction measures 6 months

7. Application for drilling operation (MDIR) 15-20 weeks

8. Public hearing and permit 3 weeks

9. Post activities Drilling/spud

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DIALOG WITH THE ENVIRONMENTAL AGENCY (MDIR)

Byrkje

Meeting with MDIR (former Klif) informing about theplanned drilling activity and how GDF SUEZ planned to carryout the sponge risk assessment

Program for the joint baseline survey including the visualsurvey was presented for MDIR

General remarks

Each well and drilling operation will have differentchallenges to be maintained and discussed; different sponges densities and environmental situation (distance, species, density,

”classification”) well specific conditions: reservoir, geotechnical, drilling program

rig specific or technical conditions

Necessary risk reduction measures and legal requirementspresented in the permit (MDIR) might therefore be differentbased on overall assessment and technical possibilities orlimitations.

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SPONGE RISK ASSESSMENT:GENERAL PRINCIPLES AND INPUT DATA

Sponge Risk Assessment carried out by Det Norske Veritas (DNV)

Input:

Resource map; mapped and analysed sponges in the area

Threshold values; sediment load

Discharges; deposition distances and thicknesses (DREAM)

Probability of current direction



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MAPPING OF THE SEABED: SURVEY STRATEGY

1. Baseline survey carriedout by DNV as a part ofa joint programbetween the operatorsin the Barents Sea2012. 3300 meters of video was

filmed and analysed (black)

2. Fugro visual mapping: covered a total distance of

approximately 14 km, intwenty 700 meter transects.

In total 1215 still pictureswere taken and classified forsponge densities and about

16 hours of video wasrecorded. (red)

Mappings carried outaccording to Guidelinefor “Mapping/Trendmonitoring” NS 9435

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The presence of deep sea sponge aggregations was visually mapped during twosurveys in 2012;



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MAPPING OF THE SEABED: ANALYSIS

DNV carried out a study of the distributionof sponges at the site

The sponge density mapping is based onboth DNV and Fugro visual survey data

Quantification of density of soft-bottomsponges was divided into four categories: Sparse/single individuals (≈ 0% sponge coverage)

Scattered (≈ 2% sponge coverage)

Common (≈ 5% sponge coverage) High (≈ 10% sponge coverage or 0.5-1 sponges

per m2)

Soft bottom sponges Hard bottom sponges

Figure Error! No text of specified style in document.-1: Categorisation of sponge habitats.

Sparse or single individuals Scattered density

Common density High density

Figure Error! No text of specified style in document.-2: Sponge density categorisation used by DNV during visual surveys.



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RESULTS OF THE MAPPING AND ANALYSIS OF SOFT BOTTOMSPONGES

Soft bottom sponges (mainly Geodia spp.) were mainly found in inscattered densities (~ 62 %)

< 1 % of was defined as high densities of softbottom sponges

Area of high sponge densities identified about 250-280 m southwest of the drill location

The highest abundances appear to be found in the shallowest areas

and only few sponges were found in the scour stripes and icebergplough marks

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MAPPING OF THE SEABED: INTERPOLATED SPONGE DENSITY

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The mapping was usedto create anextrapolated map(Kriging interpolation).

Details on the five high density sponge areas identified from the interpolations



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EXAMPLES OF TECHNOLOGIES FOR DISCHARGE OF DRILLCUTTINGS

Conventional drilling (Base case)

– Combined discharge: both to sea floor (top sections) and from sea surface (fromrig - bottom sections)

Discharge only to sea floor by use of hose (Hose case) – avoiddischarges from rig and/or transport of drill cuttings from bottom sectionsaway from the identified vulnerable fauna

Cutting Transfer System (CTS) – transport of drill cuttings from topsection away from the identified vulnerable fauna

Riser Less Mud recovery (RMR) – return of drill cuttings to the rigbefore riser is connected for discharge from rig or sending onshore forwaste handling

Byrkje:

A spread study (DREAM) and sponge risk assessment was carried out for theplanned discharges offshore

To be used as a decision support in the planning phase of a drilling campaign.

The drilling location was placed in a scours/furrow.

CTS:



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PARTICLE DISTRIBUTION SIMULATION – DREAMDEPOSITION DISTANCES AND THICKNESSES

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DREAM simulations of the planned discharges was carried out by DNV.

Base case - combined discharge: both sea floor and sea surface

Results for two of the five areas with high density:Site B2 was modeled to receive just above 0.022 mm of sediments (largest)Site B1 was modeled to receive 1.3 mm of sediments (the closest structure)

Footprint of sedimentation afterend of all discharges (accumulated).

Sedimentation categories:Green 0.1-1 mm Yellow 1-3 mmOrange 3-10 mmRed >10 mm

Black circle has a radius of 250 mbrown circle has a radius of 500 m



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SPONGE RISK ASSESSMENT: CONSEQUENCE CIRCLES

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From DREAM - selected the distances of theoutermost grid cell representing sedimentthicknesses:

>10 mm: ~64m

3-10 mm: ~118m1-3 mm: ~190m0.1-1 mm:~906m

The calculated distances are considered to be

representative if the current direction at thetime of the discharge is different thanmodeled



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SPONGE RISK ASSESSMENT: CONSEQUENCES

The consequence is assessed through individual categorization of area of thefive areas of sponge aggregations.

Graded according to size; meaning the larger continuous sponge area a higherweighting it is given in the consequence matrix.

Consequence matrix: area influenced in combination with sediment load isexpressed from Level 1 to Level 4 with the following generic description:

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Level 1: Influence on either a small areaor influence from small particle loads

Level 2: Influence on either a mediumsize area or influence from moderateparticle loads

Level 3: Influence on either a medium tolarge size area or influence frommoderate to high particle loads

Level 4: Influence on a large size area incombination with high particle loads



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SPONGE RISK ASSESSMENT: CONCLUSION

Current direction: The probability of

influencing the sponge locations with givensediment load has been conservatively set tohighest category “expected”

From the consequence matrixes all spongeareas ended in “level1”, the lowestconsequence group.

“Level 1” represents influence on either asmall area or influence from small particleloads

Analysis shows that worse case situationhave will have low influence on the “densesponge aggregation” habitat.

Conclusion:

• Based on the results from the applied methodology and background information used it is believed thedrilling campaign at Byrkje will in a worse case situation have low influence on the “dense spongeaggregation” habitat.

• No changes in the intended drilling plan.

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Base/hose case Consequence matriximpact area ratio

<20% 20-40 % 40-60 % >60%

D e g r e e o f

i m p a c t

Negligible (0.1-1mm) B1 B3 B4 B2

Low (1-3mm)

Significant (3-10mm) B5

Considerable (>10mm)

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