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Artificial Lift Analysis & Design
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The Artificial Lift Analysis & Design module in WEM provides the
capability to create artificial lift designs and analyze operating characteristics
by sensitizing on data uncertainty and future well conditions. Not only does this
prepare you to provide adequate data and guidelines to the artificial lift vendor,
you can then effectively evaluate the vendor's design to ensure what you install
in your well suits your objectives.
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Artificial Lift Analysis & Design is an add-on module to WEMStd that
upgrades the natural flow capabilities for a variety of artificial lift techniques.
The artificial lift analysis & design module is an integral part of the Well
Evaluation Model (WEM) Program. Use WEM to build well models
to optimize, troubleshoot and monitor performance during the natural flow period.
As reservoir pressure declines and/or water cut increases, rates decline to the point
that artificial lift must be evaluated. Then the WEM program is
"switched" to one of the artificial lift design modules. Input the design criteria
and run the program to obtain the design results.
Artificial lift vendors are a great source for providing their view of the best lift
design. The WEM design tool enhances this process as it provides you a means for
understanding the characteristics of a vendor's design from an independent point of
view. Who else is more qualified to run a sensitivity analysis on your well to
investigate the effect future well conditions or data uncertainty will have on the lift
design? Also remember that a vendor's design is only as good as the well information
and design criteria you provide. Running the WEM design prior to
contacting the vendor prepares you to provide sufficient well information for the
vendor to arrive at an optimal design.
After the lift system is installed and operational, monitor well performance and compare
to WEM predictions to identify conditions that warrant artificial lift
re-design or identify needed repairs.
Three lift techniques are currently integrated in WEM's Artificial Lift
Design module: Gas Lift Design, ESP Design and Jet Pump Design. Each is described in
the following sections. Information on our standalone programs for intermittent gas
lift design and plunger lift design are available on request.
Gas Lift Design
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The Gas Lift module in WEM provides the necessary tool for
you to analyze a well's response to gas lift as a lift mechanism. At
design conditions, sensitize on gas lift circulation rate and identify
the gas lift circulation rate that maximizes the well's net revenue.
When injection pressure is limited, optimize your system by determining the effect of compression ratio and injection gas distribution line flow
efficiency on well productivity.
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The unloading valve design procedure is a very flexible user-interactive
design process coupled with powerful default design optimization logic to
arrive at the best system. Key features are:
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Mandrel spacing feature ensures optimum valve designs can be
accommodated for the life of the well.
Default valve design procedures account for the effects of variable
drawdown on the formation during unloading
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Default design optimizes system to produce target rate with minimum
lift gas rate requirements.
Options accommodate constant port sizes, constant surface lift gas
pressure drops and unknown reservoir characteristics.
The Gas Lift module offers a tool for monitoring the performance of an
installed system as well conditions deviate from original design
conditions. A "Troubleshooting" module predicts which valve is open or
if multi-point injection exists based on well conditions and valve
characteristics. You can enhance the analysis by importing pressure
and temperature surveys to identify the injection point in the well.
ESP Design
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The ESP module in WEM provides a database containing pump-curves, discharge
& intake manifolds, gas separators, motor-curves, shrouds, seals and cables
for all major manufacturers. A design run includes a separate analysis for each manufacturer in the database.
The optimum solution for each manufacturer is presented from which the end user selects the desired system.
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The design procedure utilizes very accurate modeling and optimization
logic to arrive at the best system. Key features are:
Pressure losses above and below the pump are based on industry's best
multi-phase flow hydraulics predictive methods.
Number of stages required is calculated from the pump curve using an
accurate stage-by-stage analysis.
Complex effects of free gas at the suction end of the pump, high
viscosities due to low API oils or oil-water emulsions and pump rpm slip
are included in the stage-by-stage analysis.
Optimum motor and cable for the system is selected that satisfies
operating and startup power requirements while minimizing operating expense.
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For an installed pump you evaluate operating characteristics by running
a well performance analysis. In the case of a constant speed pump evaluate
changing well conditions to predict up-thrust or down-thrust situations.
With a variable speed controller installed, determine operating procedures
to keep the pump out of up-thrust and down-thrust situations.
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Jet Pump Design
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The Jet Pump module in WEM creates well performance curves for the full
range of nozzle to throat area ratios as a function of power fluid rate.
At a specified pump rate and jet area ratio, well rates are determined by balancing tubing and reservoir performance.
Accurate modeling of the power fluid hydraulic equations from the surface
and through the jet pump nozzle and mixing chamber is a key element in
determining pump discharge pressure. Jet pump performance calculations are
performed with the pump operating at peak efficiency. Corresponding well
rate, surface pressure and horsepower are computed for each area ratio as
a function of power fluid rate. Finally, system constraints are included
on the design curve that fully defines the operating envelope of the jet
pump/well system.
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