Wells 5_Maersk Introduction to Well Integrity

Nigel Snow

Well Integrity

#1

Well Integrity

17 December 2012

Agenda Philosophy Primary and Secondary Barrier Envelopes Primary and Secondary Loads Investigating Leaks and Leak Paths

Acceptable Leak Rates Questions

#2

Well Integrity

17 December 2012

Well Integrity Philosophy • Two Barrier Envelope •

Primary Barrier Envelope Breach is not acceptable

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Secondary Barrier Envelope Breach may be manageable under certain conditions

• Primary Loads and Secondary Loads

#3

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Reservoir Loads

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Water or Gas Injection Loads

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Lift Gas Loads

Well Integrity

Reference Documents

17 December 2012

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Norsok D10

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API RP90

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API 14B

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Maersk Oil Well Barrier Standard

Barrier Envelopes Well barriers are pressure-containing envelopes that prevent fluids or gases from flowing unintentionally from the formation into another formation or to surface.

The primary barrier shall contain the fluids and gases at all times during the life of well cycle, and under all load conditions

The secondary barrier shall contain the fluids and gases in the event of a breach of the primary well barrier

The well barrier envelope changes during the wells life cycle depending on the wells functionality and also well activity such as intervention

Well barrier acceptance criteria can change depending on well activity

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Well Integrity

17 December 2012

Barriers to Lift Gas

Production Casing is the secondary barrier to the reservoir

Production Annulus

Secondary barrier to Lift Gas

Intermediate Annulus

Intermediate Annulus

and

Primary barrier to Lift Gas

#5

Department

Production Annulus

17 December 2012

Testing Of Barriers •

Positive Test vs API Inflow Test

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Split Gates vs Slab Gates

Barrier Envelopes

Barrier Envelopes

#6

Well Integrity Department

17 December 2012

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Lift Gas Lines

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Instrumentation Lines

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Small Bore Fittings

Small Bore Fittings and Lift Gas Lines

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Well Integrity

17 December 2012

Primary and Secondary Loads The Primary Load is the cyclic combination of pressure, temperature, tensile and compressive loading of a barrier envelope during normal operations. For Example; Maximum closed in THP is a primary load. Maximum Lift gas pressure is a primary load.

The Secondary load is an abnormal load that is not normally seen, however in theory could be possible should several events combine at the same time to produce the effect. For example, a high pressure spike as a result of a sudden water injection breakthrough is a secondary load.

#8

Department

17 December 2012

Barrier Test Requirements Primary Loads to the Primary Barrier are assessed against the actual test pressure of that barrier divided by a safety factor of 1.1

Secondary loads to the Primary Barrier are assessed against 80% of the published yield pressure

Both Primary and Secondary Loads to the Secondary Barrier are assessed against the published yield pressure divided by a safety factor of 1.2

#9

Department

17 December 2012

Leak Investigation Objectives Confirm the presence of the leak and rule out any surface related pressure sources or piping irregularities.

Determine the leak rate at stable conditions.

Confirm wellhead seal and hanger integrity.

Determine if the leak is affected by neighboring annulus sections.

To determine the source of the pressure causing the leak.

Note: any temperature, thermal expansion effects have first to be eliminated as the cause of the increased bleed down frequency

#10

Well Integrity

17 December 2012

Perform a tank volume calculation.

Perform and record at least two pressure build up profiles of the annulus section.

Acceptable leak rates (2nd Barrier) •The leak rate is below the API-14B limit (24 lt/hr or 900 scf/hr) for SSSV. •A procedure is in place to ensure that the maximum allowable pressure limit cannot be exceeded. •The annulus bleed down frequency can be safely managed by platform personnel. •Confirmation that the temporary leak is stable over time. •Formation of a working group to investigate possible options and associated costs. •Installation of additional ESD shut down pressure sensors. •Formal Risk Assessment that may recommend other additional precautions.

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Well Integrity

17 December 2012

Questions?

#12

Well Integrity Department

17 December 2012

Detecting a leak

All these leaks are detected at surface as an increase in pressure in the wellhead at some annulus or control lines.

#13

Well Integrity

17 December 2012

Measuring a leak Gas Leak

Liquid leak

• Flow prover

• API Bucket • Stopwatch • Flow Prover

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Data logger: Records the pressure at all annulus, tubing and flow temperature over time

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Gas leaks in a controlled manner through an oriffice

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Measuring the pressure diferential before and after the orifice, the flow can be calculated

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Studying the build up profiles the depth of the leak can be estimated

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Data logger: Records the pressure at all annulus, tubing and flow temperature over time

• Many production casing leaks only exist when gas lift is introduced

The Guidelines for Annulus Pressure Monitoring and Bleed Down have been in place since 1996, the current version was last revised in November 2001

#14

Department

17 December 2012

Interpreting the Results Possible Outcomes: Production Annulus Investigation • Leak identified at SPM • Leak identified in tubing • Leak identified around production packer

Possible Outcomes: B-Annulus Investigation • Leak source identified as Production Annulus lift gas • Leak source identified as B-Annulus shoe (shallow gas) • Leak source identified as 9-5/8” micro annulus problem (main reservoir)

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Well Integrity

17 December 2012