1. Online Analysis of Continuous-Flow Gas-Lift Wells
Jim Hall – Shell Int’l E&P
21 October, 2003
ASME/API/ISO Gas-Lift Workshop

2. G/L Analysis - Art or Science ?
Its an Art!
Listen
Watch the gauge
Feel the flowline
Visualise
“Use for Force, Luke”

3. G/L Analysis - Art or Science ?
It’s a Science!
Process Variables
Pressure, Temperature, Flow
Other Data
vibration, sound
Correlate
cycle frequency, amplitude
Compare
models, previous behavior

4. Fallacies of the Art Based on individual judgement and experience
Not always consistent
Difficult to teach to others
Difficult to document and re-use
Artists don’t always like to share their skills

5. Advantages of the Science
We know more now than we did “then”
Valve Performance
“Nodal” analysis of production systems
Multiphase flow behavior
Consistent and Repeatable – rules based
Can be taught to others
Can be documented and a usable history constructed
Scientists like other people to use their discoveries

6. So, What’s the Process?
1. Build a model

7. So, What’s the Process?
2. Calibrate the Model to Reality

8. So, What’s the Process? 3. Use the Model for Surveillance
Well tests, BHP/T surveys, etc.

9. So, What’s the Process?
4. Analyse Performance

10. So, What’s the Process? 4. Take Action and Confirm Results
Install Bigger Orifice
Lower Injection Pressure
Unloading Valve Closed

11. Non-Steady State Wells are a Problem
Process Variables are just that…Variable
Production Pressure
Injection Pressure
Injection Rate
Production Rate
This means that each set of conditions must be analysed to determine the well behavior for that set of conditions.

12. But I’m BUSY! This takes TIME!
Find the problem well
Collect time-series data
Input one data set
Analyse results
Input next set of data
Etc

13. One Solution – Manual, with good tools

14. One Solution – Manual, with good tools
Nice, but what Injection pressures go with what Production pressures?

15. Online Demo

16. Better Solution – Semi-Automatic
Data displayed for each time step
Production pressure traverse
Injection pressure traverse
Valve opening and closing pressures
Valve status (open, closed, throttling)
Data set playback options
Single step forward
Single step backward
Play entire set non-stop

17. Advantages of Technique
Link to real-time system
Identify problem wells quickly
Easy movement of multiple data sets for analysis
Functionality supported by analysis tool
Receives data from real-time system
Uses existing, calibrated model for analysis
Ability to analyse as a single data set
Ability to analysis as a time series data set
Re-design as soon as problem is identified

18. What’s next? Improve real-time system functionality
Automate data transfer and analysis
“trigger” analysis when heading alarm is raised
Improve analysis tool functionality
Save plots and reports of automated analysis
Improve “VCR” functions
Present options for addressing problems