Somebody's Archie spreadsheet, copied off a laptop that left three years ago, with the exponent buried in a cell nobody can find. This calculator takes the readings you have taken off your own log and returns the saturation figures with every formula printed on the screen, and it proves the bulk-volume water by a second route that does not share the first one's arithmetic.
Porosity, true resistivity and water resistivity, with your own a, m and n. Add the gamma ray with a clean and a shale line and it gives you the linear shale volume alongside.
The formation factor, the saturation exponent, the resistivity ratio and the shale index are all printed with the numbers substituted in. You can check the arithmetic by eye without opening a cell, and so can whoever reads the sheet after you.
BVW is recomputed by an algebraically equivalent route that never forms the formation factor and never forms Sw. If the two figures disagree the app says so in red. A typed exponent or a misread resistivity shows up as a mismatch, not as a confident wrong answer.
a, m and n are fields at the top, not constants hidden in a formula. Change m and watch every figure move. The result carries the values you used into the log and the CSV, so a zone is reproducible six months later.
Every zone lands in a dated table with the depth, the inputs, the exponents, all five outputs and who ran it. Download the whole thing as CSV, including the cross-check column, for the report or the handover.
Porosity, true resistivity at the zone, and the water resistivity you are working to. Type them in as they are.
Your own values, from core or from the offset well. The figures update as you change them, so you can see how much they matter.
The second BVW route sits beside the result. Green and matching means the arithmetic held. Red means do not use the numbers.
Add the zone with a depth, initials and a note. Export the whole log as CSV whenever the paperwork wants it.
This is a calculator that shows its working. It is not an interpretation and it does not draw a conclusion about any zone. It applies the printed formulas to the numbers you type and prints the result beside the arithmetic. On screen, and in this list, it names what the model leaves out:
Built for the consultant working three wells this year, not thirty. Oil Rigs Now has been making tools for oilfield crews since 2011. A full interpretation seat is the right answer when you are picking zones for a living; it is the wrong answer for checking a saturation on a handful of wells. This one runs entirely in the browser. There is no account and no signal needed, and nothing leaves the device. Install it to a phone home screen and it opens on a location with no bars.