Is my well safe? Terje Løkke-Sørensen, CTO, add energy

Is my well safe? Terje Løkke-Sørensen, CTO, add energy

Introduction

What is? a Safe Well?.. an Unsafe Well? A well with 2 well barriers both fully intact? A well with known issues risks can be managed? A well with no HC leaks to the environment? are there any? A suspended well?

Analogy Is it safe to drive this vehicle? Is it safe to produce this well? Fuel leak detection Gas leak detection Is it safe to produce this well?

Analogy Break test Is it safe to drive this vehicle? Is it safe to produce this well? Pressure & function tests Is it safe to produce this well? Break disks > 50% worn? Uneven breaking power? Spongy response? 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). Norwegian Oil & Gas GL No.117 Guidelines for Well Integrity License Holder s system for Well Integrity applies 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. Gate Point Integrity Assessment Periodical Integrity Monitoring x A well health check should be done more than once Concept Selection & Well Design 1 Well Construction (Drilling, Completion, Testing) 2 Well Operation (Production, Maintenance, Interventions) 3 Workover (Sidetrack, Re-Completion) 4 Suspension / Abandonment 5

One way towards safe wells START: A well with unknown Well Integrity Status Assess each well barrier element In-depth assessment of potentially degraded elements Define the Well Barriers / Elements Leak path / leak rate risk analysis? Define the design / performance requirements to the Well Barrier Elements Establish overall WI categorization Perform more data gathering? Collect well data records Rectify if required END 1: Continue production END 2: Suspend / abandon

Define the well barriers 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. The well barrier consist of several elements that when connected together forms a pressure tight seal QUESTION HOW DO WE KNOW THAT THE BARRIER AND ELEMENTS ARE PRESSURE TIGHT?

Define performance requirements Check list items Casing Cement Sources: Regulator API/ISO NORSOK Operator Vendor XMAS Tree 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 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

Collect data & assess Casing Cement Sources: Operator Vendor XMAS Tree Results 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. 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

Casing Cement Formation 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 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 Leaks with approx. 35 scf/hr Category Red Orange Yellow Principle One barrier failed - the other is degraded/ not verified, or leak to surface One barrier failed - the other intact, or a single failure may lead to leak to surface One barrier degraded - the other intact Green Healthy well - none or minor issues If annulus pressure should increase -> may fracture formation What category would you chose? LMV - Leaking stem, needs regular greasing to control it Orange

What do you do? Install automatic annulus pressure bleed off system? It is a hard call Routine ROV surveys of seabed for gas seepage? Workover / side-track? Continue production? Inject cement into B-annulus? Inject heavy brine into B - annulus? Suspend well? Call my boss?

The message 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

Thank You

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