Summary of New Features in FORGAS 8

· Model Oil Systems - FORGAS coupled with the black oil reservoir simulator, IMEX, from the Computer Modelling Group, can now model crude oil/gas/water production systems in FORGAS. IMEX provides the productivity index and reservoir static pressure for each of the oil, water and gas phases as well as the fluid gravities, oil viscosity and bubble point properties for each individual well production zone. FORGAS uses these inflow performance data, plus the gathering system and wellbore configuration to calculate the flow rate of each well zone. FORGAS then passes the target phase flow rate back to

IMEX to allow it to compute the cumulative production and inflow performance conditions for the next time step. The following features are available:

a) Specify the desired rate of the target phase (oil, water or gas).

b) Specify maximum fluid limits for the contract and the desired action when exceeding the contract limit (choke worst offender or prorate production).

c) Model gas/water/oil separators, exports, imports and pressure loss facilities.

d) Define pumps either with specified power and efficiency values or with pump curves.

e) Specify field facility maximum fluid limits (for pump and separator).

f) Print summary and forecast tables for pumps, separators, imports and exports.

g) Plot oil, water or gas flow rates for wells, facilities, pipes, contracts and plants.

h) Specify wellbore facilities, such as pumps, gas lift and chokes anywhere in the wellbore. Up to 4 wellbore facilities are allowed per well.

i) Limit zones using maximum oil, water, gas limits to either shut-in the zone or choke the zone.

· Aziz, Govier and Fogarasi using Homogeneous Flow in Annular-Mist Flow - For high liquid systems (especially oil wells), we recommend the use of the Aziz, Govier and Fogarasi method using homogeneous flow in annular-mist flow to predict wellbore pressure losses.

· 3 New Equations of State from the Virtual Materials Group, Inc. (VMG) - The VMG Peng-Robinson, VMG Advanced Peng-Robinson and VMG Soave-Redlich-Kwong equations of state are now available in FORGAS by special license. The VMG Advanced Peng-Robinson equation of state is recommended for all conditions. The VMG Advanced Peng-Robinson equation of state includes the most accurate liquid density model of the 6 equations of state available in FORGAS. The Advanced Peng-Robinson equation of state is also the best one for modelling acid gas systems.

· Wellbore Facilities for Gas and Oil Wells - Include up to 4 wellbore facilities at various locations in each wellbore to simulate gas lift, downhole chokes and/or downhole pumps.

· FBOGraph Improvements - You can select to have FBOGraph display the same scale for plots using the same units, and you can save a graph template that contains your graph settings.

Summary of New Features in FORGAS 7 (September 2003)

· Multizone Commingled Production - Model up to 5 commingled zones per well. Each zone has its own reservoir connection and sandface inflow performance. Fluids (gas, water, condensate) are now specified for each individual zone. FORGAS automatically combines compositions in the wellbore to determine the composition and liquids in each wellbore segment and for the entire well.  Zones will be turned off automatically to enforce user-specified limitations (maximum water/gas ratio, maximum water invasion, maximum static pressure differential between zones). Optional flow rate constraints can be placed on individual zones (maximum flow rate, maximum sandface velocity and maximum drawdown (fixed or fractional)), which FORGAS will enforce by calculating the required surface backpressure to constrain the zones appropriately.  The optional Well Zone Summary lists the flow rate and pressure of each zone, and the limiting restrictions on each zone (e.g. drawdown) at current operating conditions.  Zone location can be expressed as elevation, measured depth or true vertical depth with respect to ground level or KB elevation.

· Wellhead Choke Facility - Choke calculations are done for single phase or two phase choke facilities located at the wellhead when provided a choke size and choke coefficient.

· Wellbore Temperature Calculations - For production wells, wellbore temperature can either be specified or calculated. The overall heat transfer coefficient can either be specified or calculated for buried, submerged or above ground wellbore segments, including up to 6 layers of insulation. The user may plot wellhead temperature as a function of well flow rate.

· Campbell Compressor Equation - The Campbell compressor equation has been added for modeling centrifugal compressors.

· ECLIPSE Interface Enhancements - FORGAS can interact with up to 5 ECLIPSE input data files simultaneously. FORGAS now automatically detects the units (field or SI) of each ECLIPSE input data file. The user can select the coupling point to be at the wellhead or at the sandface. FORGAS will now retrieve the expected time step length from ECLIPSE and use this information to limit the size of the next time step in ECLIPSE.

· Remaining Recoverable Reserves Summary - The remaining recoverable reserves for zones, wells, report groups and pools can be summarized at each time step for all types of reservoirs (including those connected to the IMEX or ECLIPSE reservoir simulators). 

· Use Flow Points Gathered on Different Dates to Calculate Deliverability Coefficients - A different cumulative production (or reservoir pressure) can now be entered for each stabilized flow rate and pressure pair, to allow both deliverability coefficients for the Conventional equation (C&n) or the LIT equation to be calculated. Previously, all pairs of flow rate and pressure had to be entered at the same reservoir pressure, which severely restricted the use of this option.

· OLGAS 2000 Added - The 2 phase version of OLGAS 2000 (from Scandpower) is available for wellbore and gathering system pressure loss calculations.

· Option to Ignore Multiphase Flow In Wellbore - The user can select to ignore multiphase flow in the wellbore of wells under artificial lift (e.g. plunger lift or blowdown). This option instructs FORGAS to keep track of the water produced, so that the water/gas ratio is available for gathering system calculations. 

· More Flexible Changes in the Development Schedule - The order of addition of well zones and plant compression can be changed on any date of the forecast. The amount of plant compression to be added can also be changed on any day.

· Model More Complicated Gathering Systems - FORGAS now supports seventh order branching. Previously, only fourth order branching was supported.

· More Accurate Deliverability Calculations - Each well is now described using up to 31 points on the wellhead deliverability curve which is used to compute the flow rate of each well. Previously only 16 points were supported.  Minimum stable flow rate calculations are now done in the direction of flow for better accuracy.  When converting flowing wellhead pressure to sandface flowing pressure, FORGAS will now calculate in the direction of flow for optimum accuracy.

· More Segments Supported in the Wellbore - The wellbore can be split into 11 segments.  Now measured depth is listed instead of true vertical depth in the input data echo, results, warnings and error messages.

· Wobbie Index Print - The Wobbie Index computed for the gas entering and exiting the plant is now printed in the Plant Gas Composition Summary.

· Handle Larger Reservoirs - Now the original gas in place and current cumulative production values for reservoirs can be up to 100 Tcf (2800 10⁹m³). The previous limit was 10 Tcf (280 10⁹m³).

· FBOExport Improvements - The available items to export are now categorized by family (Peak Demand, Actual Production, Max. Delivery, Input Data, Other) for easier selection. In the Excel file created, each sheet is labeled. The user can now select several items at once, in addition to the options to select all items or select an individual item.

· FBOGraph Improvements - Plots are now available for individual components (e.g. mole fraction of H2S over the forecast period) or individual wellbore segments (e.g. frictional pressure drop versus time).

· NeoViewer Enhancements - Enhancements in the search function allow the user to search upward or downward in the file. The item displayed is now shown in the middle of the page. Pressing the END key shows the text of the last page.

· FGI Automatic Time Backup - FGI will now automatically save the input file at timed intervals.

· FORGAS Manual Available from Within FGI - The new Help menu item provides access to the FORGAS User Manual from within FGI. The user can now select the What’s New menu item to see a summary of the new features in FORGAS.