Pipelines Servicing Mature Oil & Gas Fields

– Operational challenges to the ability to prepare and

inspect pipelines

Bryan Melan, PE

Marathon Oil UK, LLC

Oil & Gas Technology Forum 201219 April 2012Aberdeen

Operations of Pipelines with Declining Throughput

Pipelines and handling facilities primarily designed to maximise throughput

High initial rate of return and quick payout

The value of hydrocarbons, technological efficiencies, and asset life extension practices have these facilities operating at conditions unforeseen at design stage.

Pipeline product quality specifications are based upon what goes into the pipeline – not what comes out – or remains inside.

Low flowrates = low velocities

Low velocity = water and solids drop-out

Pipeline acts as a very efficient separator – long residence time

Low velocity = increased risk of failed ILI

Changes in composition of production fluid corrosive impurities – especially H2S and CO2

Some of these impurities and maintenance chemicals injected into the pipeline stream preferentially partition to the water phase creating potential downstream processing and treatment problems.

Water drop-out

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Potential Downstream Risks from high water cut

Contamination of NGL processing equipment

Liquids not to spec for saleBOD and COD contamination from water discharge

Pipeline product in

Stabilised liquid hydrocarbon out

Raw Gas

To water treatmentand discharge

The inspection contractor needs to be aware of all factors which

could affect the inspection run

Selected tool may not be capable of overcoming some obstacles

However … Tool could possibly be modified to surmount the obstacles

Or … Procedures could be developed and put in place to achieve inspection

Or … Allowances and tolerances could be put in place for data analysis taking into account existing pipeline deficiencies

Or … Additional tool runs of different technologies could achieve the inspection goals

Or … Multiple technology tools may be a solution

Pull-through tests or loop trials can provide assurances before mobilising to the field

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Obstacles to the Ability to Prepare and Inspect Pipelines

OBSOLESCENCE

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Facility Issues which Impact Effectiveness of Pipeline Cleaning

and Inspection Programmes

Operations Priorities

Mechanical Breakdowns – trap Doors, interlock systems, valves unable to isolate, prime movers and drivers (pumps and compressors)

Weather – use of overhead cranes

Vertical Launchers and Receivers – dependent upon crane availability and mechanical fitness for purpose

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Obstacles to the Ability to Prepare and Inspect Pipelines

WAX & DEBRIS

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Pipeline Cleaning

Still more of an art than science

Two basic methods – mechanical and chemical, often used in combination

Efforts to more accurately define the status of debris and deposits inside pipelines are progressing (dataloggers, condition assessment tools)

Difficulty of cleaning depends upon the product composition quality and service conditions

Cleaning refined liquid product pipelines (gasoline, etc) for ILI can be quick and relatively easy

Cleaning waxy crude pipelines can be a long difficult process

ILI data collection can be compromised by insufficient cleaning, metals not removed, or pieces of cleaning tools left behind

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Unneeded and expensive distraction from cleaning programme

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Subsea Check Valve, 27 meters water depth, 3 meters of mud cover

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Cup wear from dry running conditions

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Wax Affect on MFL Signals

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Welds at 2 kmWelds 778m -877m

Magnetiser Module ‘Cleaner’ – supplemented with injected wax

dissolver

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July 2011 December 2011

Obstacles to the Ability to Prepare and Inspect Pipelines

LOW FLOW

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Ultra-low Velocity Effect on MFL SignalsLess than 0.05 m/sec

A Simpler Way to Run Pigs

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Pipelines Servicing

Mature Oil & Gas Fields -Operational challenges to the ability

to prepare and inspect

pipelinesspect pipelines

19

Thank You for Your Attention

Questions?

Bryan Melan, PEMarathon Oil UK, LLCApril 19, 2012