3904 S-Homuth et al

Risk Management and Contingency Planning for the First Icelandic Deep Drilling Project Well in Krafla, Iceland

World Geothermal Congress 2010 – Bali, Indonesia

Sebastian Homuth Bjarni PalssonSveinbjörn HolmgeirssonSveinbjörn HolmgeirssonIngo Sass

Ri k A t d E l tiRisk Assessment and Evaluation

A l ti l l t f thi i k tAnalytical elements of this risk assessment:

Identification of initiating events

Qualitative evaluation of possible causes

Probability analysis in order to determine the probability of certain scenarios

Consequence analysis and according mitigation and action plans

Probability 0-20% 20-50% 51-75% 76-85% 86-100%yDescription very unlikely unlikely likely very likely almost sure

Impact Factor 1 2 3 4 5Impact Factor 1 2 3 4 5

Description negligible minor serious but tolerable major hazardous to

whole projectp j


O iOverview

G l i l Ri kGeological Risks Volcanic Activity Earthquake Activityq y Low Productivity

Drilling Risksg High Temperature Environment Circulation Losses Coring Operation Coring Operation Casing Failure

ConclusionsConclusions

Perspectives


G l i l Ri k V l i A ti itGeological Risk: Volcanic Activity

Eruption history gives estimate of long-term probability of renewed activity:eruptive phases are episodic, in 250-1000 year intervals, (each eruptive phase is apparently lasting 10-20 years)

Geodetic measurements: indicate relativly uniform strain accumulation along the length of the plate boundary in north Iceland A kj t i id d th lik l l ti f d ti itAskja segment is considered as the likely location of renewed activity

Krafla system is considered comparatively safe for utilization during this century

Ash-fall from distal volcanoes cannot be excluded, but large plinian eruptions are rare.

Krafla is out of reach of catastrophic floods due to volcanic melting of glacier ice12. Mai 2010 | Institute of Applied Geosciences | Chair of Geothermal Science and Technology | Sebastian Homuth | WGC 2010 | 5

A tAssessment

Probability: less than 20% - Impact factor: 5

P ti it i t l if t ti d i i ti it Prevention: monitoring natural manifestation and seismic activity

Contingency plan: from securing well and drill rig up to abandon drill siteg y p g g p


Geological Risk: Earthquake ActivityGeological Risk: Earthquake Activity

Seismic monitoring system (in operation since 1994): seismic activity within the region has remained low, largest earthquake registered: 2.6 on the Richter scale

Accumulated stresses in the region have been released

Significant duration as a function of distance to surface for different earthquake magnitude values ca. 10 sec

40Mw = 7 0

30

35

Mw = 7.0Mw = 6.5Mw = 6.0Mw = 5.5

(Björnsson et al., 2007)

15

20

25

DU

RA

TIO

N (s

)

Measured earthquakes (M ≥ 3) in the NE-region from 1930 to 2000

5

10

NE-region from 1930 to 2000 (Björnsson et al., 2007)10

010

110

20

DISTANCE (km)


A tAssessment

P b bilit (f M it d b 3) l th 20% I t f t 4Probability (for Magnitude above 3): less than 20% - Impact factor: 4

Preventive measures: monitoring seismic activity and fault movements

Contingency plan: from securing well and drill rig up to abandon drill site


Geological Risk: Low ProductivityGeological Risk: Low Productivity

Permeability in Vitismor field is above average

Brittle-plastic transition zone pconstrains the maximum depth of fracturing

Possible limit of fractured zone in Krafla at 4-5km depths

Permeable horizons intersected by wells in the Leirbotnar field in Krafla (Gudmundsson & Arnorsson, 2002)

depths

Arnason et al. (2008)


A tAssessment

P b bilit 50% I t f t 4Probability: 50% - Impact factor: 4

Consequence: impermeable formation No discharge of supercritical fluids

Mitigation measures: investigation of upper permeable zones

Contingency plan: side tracking, applying reservoir enhancement techniques (hydraulic or thermal stimulation)


Drilling Risk: High TemperatureDrilling Risk: High Temperature

H d d i ti D t d ill bit d t d ill t i Hazard description: Damages to drill bit, mud motors, drill string, mud gelation, thermal balance of circulation, logging tools

Consequences: Low rate of penetration, delay in drilling process, increasing costs

Tools / Materials Temperature Limitations [°C] O-Ring

SealDownhole Motor Sator Rubbers 175-200Seal Materials 150-190Steering Equipment 175Mud Dispersant 250-300

Seal

Mud Dispersant 250 300

modified after Saito et al. (1998)

Saito (2003)


A tAssessment

Probability: 65-75% - Impact factor: 3Probability: 65 75% Impact factor: 3

Counteractive measures: cooling well with cooled drilling fluid, maintaining a sufficient rate of circulation high temperature resistancemaintaining a sufficient rate of circulation, high temperature resistance material

C i l diff i l l i ddi i l li Contingency plan: different material selection, additional cooling capacities


Drilling Risk: Circulation Losses

Hazard: partly or total loss of drilling fluid steam kick hazard possible at any depth

Drilling Risk: Circulation Losses

Hazard: partly or total loss of drilling fluid, steam kick hazard, possible at any depth

Consequence: Stucking of the bottom hole assembly, loosing ability to cool drilling equipment/well

Profiles of wells KG-10, KG-4, KG25 and IDDP-1 (13.12.2008) with lithology, casing program and circulation loss zones (LVP 2008, modified).


A tAssessment

Probability: 80% - Impact factor: 4Probability: 80% - Impact factor: 4

Mitigation measures: analyze historic drill data to predict possible i l ti lcirculation loss zones

Contingency plan: using polymers instead of water; Barite plug, g y p g p y p gcementing


Drilling Risk: Coring OperationDrilling Risk: Coring Operation

H d d d i l ti ttti t k i h l d th i Hazard: reduced circulation gettting stuck in hole, damages the coring equipment, kick and blow hazard

Consequences: Low rate of penetration, delay in drilling process, increasing cost, loss of scientific data

(Thorhallsson, 2008)(Thorhallsson, 2008)


A tAssessment

Probability: 60 75% Impact factor: 1Probability: 60-75% - Impact factor: 1

Mitigation measure: applying the new coring barrel with increased fluid circulation capacity

Contingency plan: stop coring process and continue with Contingency plan: stop coring process and continue with conventional drilling


D illi Ri k C i F ilDrilling Risk: Casing Failure

Hazard: Casing breakouts, gdeformation or collapse

Consequences: Delay of drilling Consequences: Delay of drilling process, increase of costs

Ch i i t Chosen corrosive resistance alloys and high-strength steel are appropriate


planned casing program, LVP, 2008

A tAssessment

P b bilit 30% I t f t 4Probability: 30% - Impact factor: 4

Mitigation measures: strict inspections on material and welding process, g gstrict vertical drilling

Contingency plan: fishing back casing, cement plug and side tracking, i t i i i t b di dimaintaining appropriate bending radius


C l iConclusions

The natural geological risks arising from volcanic and seismic activity as well as meeting sufficient permeable zones are considered as comparatively minor important factors to the well completion processcomparatively minor important factors to the well completion process due to their low probability.

The main risks are assessed in the hazard of meeting circulation The main risks are assessed in the hazard of meeting circulation loss zones and material failures due to the high temperature environment.

In addition borehole failure, formation fracturing, cement and casing failure as well as problems during coring operations are assessed to failure as well as problems during coring operations are assessed to be likely, but by applying the appropriate techniques as well as mitigation and counteractive measures most of these risks can be reduced or preventedreduced or prevented.


P tiPerspectives

Lack of reliable data limits the risk assessment (for depths exceeding 2 km)

Investigate rock properties with the help of core samples are essential

Stress field, rock permeability, thermal conductivity, geochemical data is of particular interest

A detailed digital reservoir model helps to understand the behaviour and interactions of the different reservoirs, flow regimes and location of magma chamber and intrusions.


THANK YOU VERY MUCH FOR YOUR ATTENTION!YOUR ATTENTION!

IDDP-1 drillsite in December 2008

3904 S-Homuth et al

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