FAQs - PowerTools® U.S.
Questions answered in this document:
Q. Can I add my own data to a PowerTools property?
A. Yes, You are able to edit/add either Lease Header information or Lease History, which includes production data or test data. Point to a lease name in the Project Tree, right click, and select Edit. Edit the lease headers under the Lease tab and edit pressure tests and production history in the Pressure and Production tabs.
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Q. Does the program store the actual values of the forecast line?
A. No, only the curve handle positions are stored, but they are sufficient for PowerTools to redraw the forecasts. If you need the individual monthly values for the forecast, run the Lifetime Monthly Production Forecast Report.
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Q. How can I create oil and gas pricing escalations?
A. Escalations can be defined in the Settings tab. Click on the Add to Settings Tree button and select Add Escalation, or double-click on an escalation name. PowerTools supports free-format names for the escalations. Once the escalation has been defined, it can be applied to a loaded lease by selecting the escalation name in the economics tab, or it can be applied to a project-level case in the Settings tab. For example:
Hold oil price flat for two years, then escalate oil 5% to $30/bbl.
Example Oil :
Settings tab
Select Add to Settings tree, Add Escalation.
Enter name. (i.e. PriceEscOil); the Edit Escalation dialog will appear, select the following phrases in the Current Escalation Segment drop down lists:
- Do not adjust the price
- And do nothing to the price
- Until the escalation runs for 24 months
Then click on the New Segment button and select the following phrases:
- Do not adjust the price
- And escalate using an exponential percentage of 5%
- Until the price is 30
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Q. From what date are the remaining reserves calculated?
A. All remaining reserves and economic calculations are based on the EFFECTIVE DATE that can be set in the Settings tab, Economics branch. The curve handle coordinates determine the slope of the forecast, which is used in calculating the remaining reserves.
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Q. Where does the program get the values used in calculations?
A. On adding a new lease to a project, PowerTools reads the following parameters from the data source (PI/Dwights PLUS CD, 298 file, or DP2 file) if available:
- Upper and lower perforations
- Gas gravity and API oil gravity
Base Pressures and Surface temperatures are applied according to the standards specified by each State.
PowerTools calculates the following parameters while adding the lease to the project:
- Net pay = lower perforation - upper perforation
- Well Depth = (lower perforation + upper perforation)/2
- >Reservoir Temperature = surface temperature + ((temperature gradient/100)*welldepth)
PowerTools calculates the following parameters the first time the lease is loaded by double clicking on it:
- GOR
- Yield
- Reservoir Pressure
These values are recalculated by PowerTools only on demand. To recalculate a value, point to the parameter name in the volumetrics tree, right click, and select Recalculate.
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Q. How does PowerTools calculate the Z factor?
A. PowerTools calculates the real gas deviation, or Z factor (Z), for hydrocarbon gases. The technique used by this program was developed by Dranchuk, Purvis, and Robinson. The Benedict-Webb-Rubin equation of state is fit to the Z factor surface defined by the Standing-Katz Z factor correlation. The resulting nonlinear equation is then solved for Z as a function of reduced temperature and pressure using Newton-Raphson iteration. The Dranchuk, Purvis, and Robinson correlation has the lowest average error of the eight most commonly used methods for estimated Z factors.
References:
Dranchuk, P. M., Purvis, R. A. , and Robinson, D. B. "Computer Calculations of Natural Gas Compressibility Factors Using the Standing and Katz Correlation," Institute of Petroleum Technical Series, No. IP 74-008, 1974.
Takacs, G., "Comparisons Made for Computer Z-Factor Calculations," Oil and Gas Journal, Dec. 20, 1976, pp. 64-66.
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Q. How does PowerTools calculate pseudocritical temperature and pressure?
A. PowerTools estimates the pseudocritical temperature and pseudocritical pressure from gas gravity for both condensate fluids and miscellaneous reservoir gases. The calculated values for Tc and Pc are corrected for sour gas content with a Wichert-Aziz correction.
References:
Standing, M. B., Volumetric and Phase Behavior of Oil Field Hydrocarbon Systems, 1977, pp. 26, 122.
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Q. How does PowerTools calculate the gas formation volume factor?
A. The gas volume factor is calculated using the ideal gas law with a Z factor correction, using standard pressure and temperature as specified by the state, otherwise using a temperature of 60°F and a pressure of 14.65 PSI.
References:
McCain, W. D., The Properties of Petroleum Fluids, Petroleum Publishing Co., 1973, pp. 122-124
Amyx, Bass, and Whiting, Petroleum Reservoir Engineering, McGraw-Hill, 1968, p. 30.
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Q. How does PowerTools calculate the oil formation volume factor?
A. PowerTools estimates the oil formation volume factor at the bubble point, above the bubble point, and below the bubble point. The oil formation factor is used to correct to surface barrels of oil from reservoir conditions in the volumetric calculations.
References:
Ramey, H. J., "Rapid Methods for Estimating Reservoir Compressibilities," Journal of Petroleum Technology, April, 1964, pp. 447-454.
Vasquez, M., and Beggs, H. D., "Correlations for Fluid Physical Properties Predictions," Journal of Petroleum Technology, June, 1980, pp. 968-970.
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Q. How does PowerTools calculate the bottom hole pressure?
A. PowerTools records both the shut in tubing pressure and bottom hole pressure. PowerTools also determines whether the bottom hole pressure was calculated or measured. If the bottom hole pressure was measured, then the system uses the pressure as given. If the bottom hole pressure was calculated, then PowerTools will recalculate the bottom hole pressure based on input and default values. PowerTools uses an iterative procedure to calculate bottom hole pressure based on the Cullender-Smith technique. This technique consists of iterations based on a calculation of the average Z-factor for the gas conditions, well depth and temperature.
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Q. What are the volumetric calculations that are used?
A. They are:
Oil in place = ( 7758 * porosity * (1 - Water saturation) * acres * net pay ) / Oil volume factor
Gas in place = ( 43.56 * porosity * (1 - Water saturation) * acres * net pay ) / Gas volume factor
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Q. Can I transfer data from PowerTools into Aries?
A. Yes. An interface utility is included on the PowerTools CD. This utility can create a DOS or Windows Aries project from a PowerTools database, or a PowerTools project from a DOS or Windows Aries database.
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Q. How can I customize graph titles?
A. Right click on a graph to open the graph properties dialog. In the Text tab, click on the ... button to show a list of parameters. Select a header parameter to add to the graph title.
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Q. Can PowerTools databases be used with Microsoft® Access?
A. Yes, but do not make any design modifications to existing fields in the database, or the database will become incompatible with PowerTools.
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Q. Why would I have trouble moving the handles on a hyperbolic projection?
A. This is probably because the curve is too flat, and PowerTools constrains the curve to a valid hyperbolic solution. Toggle the curve to exponential, give the curve some (negative) slope, and then toggle back to hyperbolic. Or — drag the right-most curve handle downward, and then drag the left-most curve handle upward, and the projection should become easier to edit.
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Q. What are the .LDB files associated with the project databases?
A. These files are generated by Access, and they maintain the lock information for databases on a multi-user network. An .ldb file can be deleted if no one currently has it open. If needed by Access, it will regenerate the file.
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Q. Why does my summary forecast have "stairsteps"?
A. When summing multiple leases, the historic production from each lease is summed on a phase-by-phase basis. The forecasts which are defined for each phase for each lease are also summed. Before summing the leases, all adjustments to the decline-curve forecasts should be made on a lease-by-lease basis. Differing start dates will produce a stair-step upward profile, where each step corresponds to the initial handle position for a curve contributing to the sum. You can optionally start the display of the summary forecast at the effective date. Right click on the graph, select Properties, General tab. (A stair-step downward profile results as each lease reaches its economic limit, illustrating the decrease in number of economic leases.) A forecast summed within PowerTools cannot be modified, as there is no means for allocating the production back to the lease level.
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Q. How can I perform a decline curve analysis on a summary of leases?
A. Select some leases in the Leases tree, then click on the (summation) button, and select Create Summary Lease. Provide a name for the new lease, and it will be added to the Lease Tree. Load the new lease, and go to the RT graph to perform decline analysis.
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Q. Why am I not getting a forecast on the Rate/Time graph for a product?
A. If a lease has an Inactive status, forecasts are not drawn. You can use the Edit Lease Header Dialog to change the lease status to Active, to draw the forecasts. For Oil and Gas curves on Active leases, the forecast will not project into the future if the curve slope is positive. Only water curves are allowed to project with a positive slope (note: PowerTools "caps" monthly water production at 1,000,000,000 bbls, to prohibit unreasonable forecasts from water flood projects).
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Q. Can I adjust line widths on my plots for the forecast?
A. In the Rate/Time Graph, the line-width options modify only the display of the historic production data; the line-widths of the forecasts may not be modified. However, in the Custom Graph, the line-widths of the forecasts may be adjusted, in addition to the line-widths of the historic data.
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Q. How much disk space is required to install and use the products?
A. PowerTools requires approximately 20 MB of disk space. Additional disk space is required if map files (up to 420 MB for the entire U.S.) and/or videotutorials (20 MB) are installed. Additional, temporary disk space is also required for uncompressing files during the installation of PowerTools . If disk space is not adequate, an error message will be issued during the installation. Delete some files to free some disk space, or install PowerTools on a system with adequate resources.
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Q. What are the different levels of help provided with the products?
A. A standard Windows help file is installed with PowerTools . Multimedia tutorials are also available. These can be played directly off the CD from the PowerTools Startup Options, or installed to a local or network disk and viewed from within PowerTools via the Tutorials option in the Help menu or accessed via the internet.
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