Automating Flow Control on Gas Lift Wells Comparison of Alternative Methods

South American Production Facility

Conventional Automation Electric Actuated Choke Valve Orifice Plate Flow Measurement Flow Computer

Conventional System Schematic

Flow Meter

Well Optimization Curve

System Problems At lower injection rates (below 2.5 MMSCFD) the well produced intermittent flow

Production Data with Conventional Automated System

Conventional System Characteristics Advantages Simple Installation Uses Existing Hardware Inexpensive No Gas Emitted Operates at Last Set Point on Loss of Power Disadvantages Requires Piping Modifications Slow Actuator Speed of Response Deviations from Set Point Actuator Moves in Discrete Increments (2% typical) Very Small Movements Not Possible

StarPac Integrated Control System

Installation Schematic

Fail in Place Lockup System Activates on loss of power or gas supply pressure

SCADA Communication Scheme

System Communication Schematic

Connecting StarPac to Bristol Babcock RTU

RTU to Radio Connection

Operator Interface

StarPac System Installation

StarPac Characteristics Advantages Simple Installation No Piping Modifications No Deviation from Set Point Fast Speed of Response PID loop runs 16 times/sec Actuator can move in small increments (.1% typical) Simple System Integration Operates at Last Set Point on Loss of Power Disadvantages Requires Regulated Gas for Supply Gas Emitted

Production with StarPac

Production Comparison (based on $25/bbl)

Production Comparison

Results Crude Production Increase = 4.3% Gas Usage Reduction = 3.3% System Payback = 12 days Potential Gas Reduction = 24% (Change avg. rate from 2.9 to 2.2)

Why the Improvement? Speed of Response & Repeatability StarPac holds closer to flow set point when system instabilities occur Changing gas supply pressure Changing flow line or tubing pressure Stability becomes more critical as flow rate decreases System is more likely to get upset/unstable at minimal flow rates Smaller deviations can cause instability