Post on 09-Apr-2018
transcript
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.
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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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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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