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Version 1.0 screenshot

Volume* is a volumetric calculator app for Android. It was built in Google App Inventor and made available in the Android Market on 4 May 2011.


The app is very simple. It is a straightforward calculator, with lookup of geometric correction factor and formation volume factor. It is designed to be handy, perhaps a little didactic. But it was mostly an experiment in creating applications.


Link to YouTube video
Watch the tutorial video at YouTube.com
Scan to visit the Market and install

Version 3.2

  • Released 13 November 2011
  • Substantially changed the More... view, which now takes up the whole screen
  • Option to not remember the Imperial units setting from session to session
  • Option to not remember the benchmark crude choice from session to session
  • Option to provide a default email address (remembered from session to session)
  • Moved Email button to main screen; duplicated Store button on Main screen
  • Store button now does not accept a blank response, which cancels the dialog; use long-press to save an unnamed prospect
  • Fixed a small bug with a notification for Risk*

Version 3.1

  • Released early November 2011
  • Added option to calculate a value for Bg, given pressure, temperature, and Z factor

Version 3.0

  • Released 12 October 2011 (updated to 3.0.2 on 26 October)
  • We have added gas volumetrics
  • The app grabs the latest gas price, as for oil (Nymex ticker symbol NGxxx.NYM, where xxx is a date code, set for 45 days in the future)
  • Note we had to move the Imperial toggle to the 'More...' menu
  • Also in the 'More...' menu: other Benchmark crude price options (Brent, Dubai, and Canadian Heavy, with Nymex ticker symbols BZ, DC, and WCC respectively)
  • You can provide Bg or expansion factor for gas (e.g. 0.004 or 250)
  • In gas mode we report barrels of oil equivalent as well as scf and Sm³
  • Note that Risk* also gives boe for now, even though it's labelled as bbl
  • Note we changed the order of N:G and porosity, and made the variables italic and more 'mathy'


Use rock volume

You can use gross or net rock volume instead of area × thickness by simply leaving Thickness blank and using the Area field for rock volume. If you want net rock volume, leave N:G blank as well.

Use a custom geometric factor

There is no way to enter a custom geometric factor in the Relief box, so just leave it blank and use the Fudge Factor.

Use a recovery factor

Use the Fudge Factor field.

Use some crazy units

Not recommended, but all these parameters are simply multiplied according to the equation on the Calculate button, so if you can keep track, feel free to use any units you like.

Compute uncertainty or risk

Stay tuned for our next version of the app.


The app computes oil volume V according to the equation

Area A or Volume
The mapped area of the prospect, in km2 (or acres, if Imperial is checked). Alternatively, you can enter the gross (or net) rock volume of the prospect, in km3 (or acre-feet). If you enter a volume, don't enter anything in Thickness (it defaults to 1 in this case). If you enter the net rock volume, don't enter anything in N:G (defaults to 1).
Thickness T or blank
The stratigraphic thickness of the gross reservoir interval, in m (or ft). Leave it blank if you entered a rock volume in Area. If you enter a value for Relief (see below), then thickness must be less than relief. If it isn't, thickness will be reduced to be equal to relief (you will see a notification). This is because the relief controls the height of the column, and thus the effective thickness (since we don't have a field for column height).
The structural relief of the trap, sometimes called the height of the closure, in m (or ft). It's just the vertical distance between the crest and the spill point. It is used to calculate the geometric correction factor, nothing else. If you prefer, you can just enter a correction factor directly—the app assumes any number below 1.0 is a geometric correction factor. If you don't want to use a correction factor, leave it blank to use the default value of 1.0.
Geometry G
Select the gross sectional shape of the prospect—a rounded dome (like half a soccer ball) or a flat-topped container (like a soup dish). Select the one most like your prospect. If you just want a flat slab, leave relief blank. The geometric correction curves are shown in the figure (right).
Geometric correction factor.png
Porosity φ
Enter a decimal fraction (sometimes called porosity units, p.u.). Values of 0.05 to 0.30 are typical.
Net to gross N:G
Enter a decimal fraction. Leave blank if you entered net thickness or net rock volume above. Net to gross can be very difficult to define accurately.
Oil saturation SO
Enter a decimal fraction. Values of 0.5 to 0.9 are typical.
Volume factor BO
The formation volume factor, or shrinkage factor, is the ratio of a barrel of oil in reservoir conditions to the same oil in surface (so-called stock-tank) conditions: 25°C and 1 atm. Use the list to choose high GOR (high shrinkage) or low GOR (low shrinkage) oil, heavy oil (very low shrinkage), or override with any value you like. Typical values are between 1 and 1.7.
Volume factor BG
If you are using the gas option, we compute the gas volume factor from reservoir pressure P, temperature T, and Z factor Z[1]:
Fudge factor F
If entered, this will be factored into the result. You could use it for recovery factor, for example. Typical values of recovery factor are between 0.2 and 0.6.
Oil price 
If you are online via WiFi or cellphone data, then the app will fetch the future crude price from NYMEX (for 45 days hence). If it fails to do this for some reason, the field will be blank (with a message web error). Whether it succeeds or not, you can enter a price of your own if you wish. It is simply multiplied by the volume to get the total value in the ground, which is displayed directly below the price. If left blank, then the value is not computed. Sorry, entering a price of your own does not affect the actual oil price on the NYMEX commodities market.
Imperial units
Switches to Imperial units for Area (or Volume), Thickness, and Relief.


Volume handy cheatsheet.png

Bugs and deficiencies

  • The app has not been tested on many devices, only a Samsung Nexus S and Samsung Captivate
  • The background image ('graph paper') squashes when the keyboard pops up
  • The popup keyboard has Done instead of Next, so there's no way to skip to the next field without tapping the field itself (new in 1.1.2); probably an App Inventor bug
  • Sometimes the keyboard comes up as the full, not numeric, keyboard; probably an App Inventor bug
  • There is no sanity check on numbers, so for example φ can be anything at all
  • The 'click' sound for the Calculate button doesn't work any more :(
  • I should replace pressure units of psia with psi and change the symbol to Pa

For future release

  • Handle uncertainty, eg with Monte Carlo simulation (probably via a web API)

See also


External links