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Gas-Lift Surveillance

Tools of the Trade

Jim Hall

5 February, 2002ASME/API Gas-Lift Workshop

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Surveillance

Close watch kept over someone or something (as by a detective)

French, from surveiller to watch over, from sur- + veiller to watch, from Latin vigilare, from vigil - watchful

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Gas-Lift Well Surveillance

The process of keeping a close watch

over a gas lift well or wells.

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What do these items have in common?

• A lawn chair• Ice• A glass• Scotch whiskey

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They are all Tools

They are tools that were regularly used by Hugh Garrett,

one of the founders of modern gas lift,

to troubleshoot a gas-lift well.

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Personal Tools

•Touch Hot or cold (misleading)

Vibration

•Sound Gas or liquid ?

•Taste (!) Fresh or Salty ?

•Sight Condensation, ice

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Personal Tools•Advantages

Easy starting point

No cost

No risk to well, safe for operator

•Disadvantages

Highly subjective

Rarely definitive

Difficult to document and transfer

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Simple Surface Tools•Gauges

Pressure

Temperature

IR remote sensors• Flow Meters

Gas

Liquid•Recorders

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Simple Surface Tools•Advantages

Extremely valuable information

Easily recorded and shared

•Disadvantages

Proper range

calibration and maintenance

wellsite security

sample intervals vary

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Complex Surface Tools

•Automation Systems

SCADA - press., temps, rates, controls

DCS - larger scale and complexity

Real-Time Lift Gas Optimisation•Remote Sensing

Video

UAV - Unmanned Aerial Vehicle

Satellite - AERA monitors subsidence

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Complex Surface Tools•Advantages

provide easy access to large data sets

enables remote operations

improved response to upsets

Reduction in HSE exposure of staff•Disadvantages

maintenance & calibration are critical

significant CAPEX

IT tools change constantly

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Simple Downhole Tools•Acoustic Well Sounder

unloading, max. unloaded depth•CO2 Tracer

injection depth / depths•Markland Pressure-Pulse

injection depth•“Whistle” Valve

injection depth

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Simple Downhole Tools•Advantages

non-intrusive, low well risk

indicates possible or actual lift depth

relatively low HSE exposure•Disadvantages

Acoustic well sounder is inconclusiveCO2 Tracer in development

Pressure Pulse in development

Whistle Valve only a concept

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Complex Downhole Tools•Downhole Pressure & Temperature survey

mechanical, electronic, not continuous•Production Log

continuous press., temp., flow•Permanent Downhole Gauge

single point pressure and temperature•Surface-Controlled Gas-Lift Systems

tubing and wireline retrievable avail.

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Complex Downhole Tools•Advantages

accurate

dependable

definitive answers

surface controlled•Disadvantages

Well entry? High risk to well

No well entry? Cannot service

Increased value carries increased cost

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Analysis Tools•Gas Lift Slide Rule - Texaco

•Transient Simulation software

•Single-well system analysis software

•Multi well system analysis software

•Full-Field models

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Analysis Tools•Advantages

Improves productivity

More Science - Less Art•Disadvantages

Garbage-in Garbage-out

slide-rule intuition has been lost

Analysis Paralysis

Must calibrate and maintain models

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No Substitue for Experience!

A tool in the hands of an inexperienced user often does more harm than good.

By 2008 - 60% of E&P company expertise will retire or move out of the industry

Our challenge is not only to develop the tools, but to put them in the hands of staff who can use them to the fullest.