Is my well safe? - NORWEP · Well Integrity Assessment (Health Check) • Well Integrity Assessment...
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Transcript of Is my well safe? - NORWEP · Well Integrity Assessment (Health Check) • Well Integrity Assessment...
Is my well safe? Terje Løkke-Sørensen, CTO, add energy
Introduction
What is …?
A well with 2 well barriers – both
fully intact?
A well with known issues – risks can
be managed?
A suspended well?
… a Safe Well ?
A well with no HC leaks to the
environment?
.. an Unsafe Well ?
are there any?
Analogy
Is it safe to drive this vehicle?
Is it safe to produce this well?
Is it safe to produce this well?
Gas leak detection Fuel leak detection
Analogy
Is it safe to drive this vehicle?
Is it safe to produce this well?
Is it safe to produce this well?
Break test
Break disks > 50% worn ?
Uneven breaking power ?
Spongy response ?
Pressure & function tests
Leak rate > 900 scf/hr ?
More than 5 open/closure cycles before a good test can be achieved ?
Analogy
Is it safe to drive this vehicle?
Is it safe to produce this well?
The WOMP should demonstrate that
there is a system in place to manage well integrity and well activities for
the life of the well(s).
License Holder’s system for Well Integrity applies
Norwegian Oil & Gas GL No.117 Guidelines for Well Integrity
“Semi” - uniform classification
criteria
Well Integrity Assessment (Health Check)
• Well Integrity Assessment is a thorough evaluation of
the primary & secondary well barriers’ compliance
with standards and ability to contain pressure based
on design, test results, measurements and
observations.
• ISO/TS 16530-2 and NORSOK D-010 well integrity
standards requires this assessment.
• The results can be used to prioritize wells that require
immediate attention, i.e. workover or P&A, or decide if
a well can be kept on production.
x Gate Point Integrity Assessment
Periodical Integrity Monitoring
3
Well Operation (Production, Maintenance, Interventions)
A well health check should be done more
than once
5
1
2
4
Well Construction (Drilling, Completion, Testing)
Concept Selection & Well Design
Workover (Sidetrack, Re-Completion)
Suspension / Abandonment
One way towards safe wells
START: A well with
unknown Well Integrity Status
Establish overall WI categorization
Define the design / performance
requirements to the Well Barrier
Elements
Collect well data records
Assess each well barrier element
Rectify if required END 1: Continue
production END 2: Suspend /
abandon
Define the Well Barriers / Elements
Perform more data gathering ?
In-depth assessment of
potentially degraded elements
Leak path / leak rate risk analysis ?
Leak path / leak rate risk analysis ?
Perform more data gathering ?
Define the well barriers
The well barrier consist of several elements that when connected together forms a pressure tight seal
Primary barrier – the first line of “defense” that prevents flow
Secondary barrier – the last line of “defense”
If the primary barrier fails – then we have ….
QUESTION
HOW DO WE KNOW THAT THE BARRIER AND ELEMENTS
ARE PRESSURE TIGHT?
Define performance requirements
Sources: RegulatorAPI/ISO NORSOK Operator Vendor
Casing Cement
Initial verification: • Quality -> API / ISO, gas tight • Length -> min. 50 m • Strength –> temp. resistant • Bonding / sealing ability -> pressure
test (LOT) or bond logging (CBL) Monitoring / Failure indicator: • HC / pressure build-up in B or C
annulus
XMAS Tree
Initial verification: • Quality -> API / ISO standards • Function testing -> manual &
automatic valves, ESD • Sealing ability -> low & high pressure
test Monitoring / Failure criteria: • Valve leak-rate exceeds 0 - xx SCF/hr • Leak through body / seals / outlets • Failing function & ESD tests
Check list items
Collect data & assess
Casing Cement
Initial verification: Quality -> API / ISO, gas tight Length -> min. 50 m ? Strength –> no silica to prevent
strength retrogression Bonding / sealing ability -> pressure
test (LOT) Monitoring Failure indicator: ! Pressure build-up in B annulus , gas,
max. pressure 20 bar – maximum allowable is 45 bar.
Sources: Operator Vendor
XMAS Tree
Initial verification: Quality -> API / ISO standards Function testing -> manual &
automatic valves, ESD Sealing ability -> low & high pressure
test Monitoring Failure criteria: HMV leak-rate is 20 SCF/hr <26 ! LMV very small gas leak through
stem
Results
In depth analysis of failures
• The casing cement is an element in the primary and secondary barrier -> is there an alternative secondary barrier?
• Gas in annulus has same signature as reservoir gas-> leak through cement?
• Pressure in annulus is stable and below maximum allowable (set by Operator)
• Leak rate is estimated to 35 scf/hr - no max defined
• High temperature may reduce cement’s compressive strength over years -> increased leak rate?
Gas
Form
atio
n
Cas
ing
C
em
en
t Results The estimated formation strength at
the intermediate casing exceeds the current annulus pressure @ shoe
If the formation fractures -> vertical fractures are very unlikely
An alternative secondary barrier can be qualified
Reliability data ?
Perform well integrity categorization
LMV - Leaking stem, needs regular greasing to control it
If annulus pressure should increase -> may fracture formation
Leaks with approx. 35 scf/hr
Orange
What category would you chose?
Category Principle
RedOne barrier failed - the other is degraded/
not verified, or leak to surface
OrangeOne barrier failed - the other intact, or a
single failure may lead to leak to surface
Yellow One barrier degraded - the other intact
Green Healthy well - none or minor issues
What do you do?
Continue production ?
Suspend well ?
Install automatic annulus
pressure bleed – off system ?
Inject cement into B-annulus ?
Inject heavy brine into B -
annulus?
Routine ROV surveys of
seabed for gas seepage ?
Workover / side-track?
Call my boss?
It is a hard call
Knowing the integrity status of your wells is a must – how can you otherwise manage risks?
Use a holistic and consistent system combined with skilled persons to perform the assessment – compare apple with apples !
Adapt well barrier performance requirements from recognized well integrity standards – supplement with your own …
Manage the high risk wells - have contingency plans ready,
… so when the Regulator ask you “ Is it safe?”
… your answer is …
The message
=
Thank You
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