Text Box:  GasPal

Contents

General Functions. 1

Special Production Modes. 2

GasPal Short and Long Term Simulations. 3

Simulation Cells. 4

Flow Rate Modeling. 4

Backout Calculations. 5

Compressor Modeling. 6

Storage Modeling. 7

 

General Functions

For storage or production reservoirs GasPal can

1.    Accurately predict performance of gas production or storage reservoir-compressor-pipeline systems.

2.    Simulate injection and production or a mixture of the two,    providing full storage scheduling flexibility

3.    Simulate complex surface network including splits, loops and multiple offtake points

4.    Simulate injection and production or a mixture of the two,    providing full storage scheduling flexibility

5.    Model 1, 2, 3 phase flow in formation, tubing and surface lines

6.    Computing speed that allows sensitivity planning runs “w/o limit”; for storage hourly/daily scheduling of compressors for production and injection. Schedules obtained are efficient and economic.

7.    Provide a convenient interface for inputting data, cut & paste history match data from Excel, smoothly manage restart files.

8.    Generate a full gamut of output graphs and tables to export results to Excel

9.    Storage database allows operations to be quickly rescheduled in response to new opportunities or unexpected changes in available equipment and/or supply/demand requirements

Special Production Modes

GasPal has the following special production modes for European gas providers

1.    Nomination Run: Both constrained and unconstrained potentials (capacities) are calculated first.  GasPal then nominates a production rate for each month with margin and well work considered.

2.    DCQ Run: GasPal calculates the Daily Contract Quantity with required swing for each month. Users can specify DCQ length to be 3, 6 or 12 months.

 

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GasPal Short and Long Term Simulations

  1. Short-term operation: hourly time steps for two weeks. Useful for immediate injection/withdrawal planning.
  2. Mid-term planning: daily time step for one year. Useful for overall storage planning.
  3. Long-term production: weekly time for 7 years or monthly time step for 30 years. Useful for regular gas reservoir production or blowdown.

 

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Simulation Cells

 

GasPal uses GRIDDER to divide a reservoir into arbitrary simulation cells. Faults can be incorporated in the simulation grids.

 

 

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Flow Rate Modeling

  1. Regular k/h Darcy and psuedo pressure for formation, multiple phase flow for tubing
  2. Empirical method C/n for formation and multiple phase flow for tubing
  3. Empirical methods for both formation and tubing, AFBC option

 

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Backout Calculations

 

When gas from a new source (e.g. wells from other reservoirs) is interjected into a surface network, the new gas causes additional pressure drop through the network. The higher pressure propagates to the wellheads of existing wells to cause rate drop from those wells. GasPal dynamically calculates the rate and pressure at every surface pipe and vertical tubing string. The rate reduction because of new gas is accurately calculated and displayed.

 

In the following example, reservoir JUN joins the network at month 36. The new gas causes a higher pressure at node 1. Consequently, higher wellhead pressures at wells of reservoir SEN cause a rate reduction in the same reservoir.

 

 

 

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Compressor Modeling

A compressor can be installed at any node in the surface network. A compressor installation schedule controls how compression is available at any given time. The following example shows that a compressor installed at month 18 causes lower wellhead pressure and higher production rate.

 

 

 

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Storage Modeling

 

GasPal models both withdrawal and injection for storage reservoirs.  The following example shows the injection /withdrawal rates and reservoir pressure for 365 days. Users specify injection, withdrawal or idle for every time step (hourly, daily, weekly or monthly.)  Daily time step is good for general, annual planning; hourly time step can be used for tactic (weeks) operation planning.

 

 

  

 

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