Copyright 2001 SIEP B.V. Online Analysis of Continuous-Flow Gas-Lift Wells Jim Hall – Shell Int’l E&P 10 February, 2004 ASME/API/ISO Gas-Lift Workshop

Copyright 2003SIEP B.V. Its an Art! Listen Watch the gauge Feel the flowline Visualise “Use for Force, Luke” G/L Analysis - Art or Science ?

Copyright 2003SIEP B.V. It’s a Science! Process Variables Pressure, Temperature, Flow Other Data vibration, sound Correlate cycle frequency, amplitude Compare models, previous behavior G/L Analysis - Art or Science ?

Copyright 2003SIEP B.V. 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

Copyright 2003SIEP B.V. 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

Copyright 2003SIEP B.V. 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.

Copyright 2003SIEP B.V. But I’m BUSY! This takes TIME! 1. Find the problem well 2. Collect time-series data 3. Input one data set 4. Analyse results 5. Input next set of data 6. Analyse results 7. Etc 8. Etc

Copyright 2003SIEP B.V. One Solution – Manual, with good tools

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

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)

Copyright 2003SIEP B.V. 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

Copyright 2003SIEP B.V. 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

Copyright 2003SIEP B.V. 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