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Online Analysis of Continuous-Flow Gas-Lift Wells. Jim Hall – Shell Int’l E&P 10 February, 2004 ASME/API/ISO Gas-Lift Workshop. G/L Analysis - Art or Science ?. Its an Art! Listen Watch the gauge Feel the flowline Visualise “Use for Force, Luke”. G/L Analysis - Art or Science ?.
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Online Analysis of Continuous-Flow Gas-Lift Wells Jim Hall – Shell Int’l E&P 10 February, 2004 ASME/API/ISO Gas-Lift Workshop
G/L Analysis - Art or Science ? • Its an Art! • Listen • Watch the gauge • Feel the flowline • Visualise • “Use for Force, Luke”
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
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
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
So, What’s the Process? • 1. Build a model
So, What’s the Process? • 2. Calibrate the Model to Reality
So, What’s the Process? • 3. Use the Model for Surveillance • Well tests, BHP/T surveys, etc.
So, What’s the Process? • 4. Analyse Performance
So, What’s the Process? • 4. Take Action and Confirm Results • Install Bigger Orifice • Lower Injection Pressure • Unloading Valve Closed
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.
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 • Analyse results • Etc • Etc
One Solution – Manual, with good tools • Nice, but what Injection pressures go with what Production pressures?
Better Solution – Semi-Automatic • 1. Automated identification of problem wells – Don’t look at ALL the wells… Note: Screen Shots taken from a static system (offline)
Better Solution – Semi-Automatic • 1. Automated identification of problem wells - Just look at the PROBLEM wells Note: Screen Shots taken from a static system (offline)
Better Solution – Semi-Automatic • 2. Confirmation of automated identification Note: Screen Shots taken from a static system (offline)
Better Solution – Semi-Automatic • 3. Zoom on a window of data Note: Screen Shots taken from a static system (offline)
Better Solution – Semi-Automatic • 4. Package the data for an analysis tool Note: Screen Shots taken from a static system (offline)
Better Solution – Semi-Automatic • 5. Confirm that the data is correct and Send Note: Screen Shots taken from a static system (offline)
Better Solution – Semi-Automatic • 6. Analysis tool starts, selects the well and presents a “VCR” frame control for playback of data, step by step Note: Screen Shots taken from a static system (offline)
Better Solution – Semi-Automatic • 7. For each step forward in time, the latest and previous traverses are displayed. Note: Screen Shots taken from a static system (offline)
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
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
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