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Monday
Mar072011

## Rock physics cheatsheet

Today, I introduce to you the rock physics cheatsheet. It contains useful information for people working on problems in seismic rock physics, inversion, and the mechanical properties of rocks. Admittedly, there are several equations, but I hope they are laid out in a simple and systematic way. This cheatsheet is the third instalment, following up from the geophysics cheatsheet and basic cheatsheet we posted earlier.

To me, rock physics is the crucial link between earth science and engineering applications, and between reservoir properties and seismic signals. Rocks are, in fact, a lot like springs. Their intrinsic elastic parameters are what control the extrinsic seismic attributes that we collect using seismic waves. With this cheatsheet in hand you will be able to model fluid depletion in a time-lapse sense, and be able to explain to somebody that Young's modulus and brittleness are not the same thing.

So now with 3 cheatsheets at your fingertips, and only two spaces on the inside covers of you notebooks, you've got some rearranging to do! It's impossible to fit the world of seismic rock physics on a single page, so if you feel something is missing or want to discuss anything on this sheet, please leave a comment.

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Evan - looks great! Guess I taught you well :)

Doug

March 8, 2011 | Doug Schmitt

If you are looking for ideas for new cheatsheets, I would suggest one for all the conversion factors people carry around in their heads e.g. m3 to barrels, m3 to ft3 etc. And what are the STOIIP/GIIP equations (nice graphic potential).
On the seismic side, what is the wavelength of a typical wavelet (the question always asked of the geophysicist when staring at the cliff-face outcrop)?

March 14, 2011 | Peter Rowbotham

@Peter: Thanks for the suggestions! We did cram a few conversion factors onto the first cheatsheet, but it was far from complete. I'd really like to try building a little mobile application for this, as the table could get unwieldy. As for the wavelength idea - I like it. Wavelength is under-appreciated, in my opinion, as it really controls resolution. Cheers!

March 14, 2011 | Matt Hall

Peter, great suggestion about unit conversions and volumetric calculations. I would love to craft something useful. Something incorporating uncertainty would be ideal.

Wavelength: geophysicists usually speak of wavelengths and dominant frequency with respect to the time domain and frequency domain, respectively. So, I agree with you, some general rules of thumb should be at hand when folks are smashing an outcrop with their rock hammers (in the depth domain). Stating that a seismic trace has a wavelength in milliseconds, or worse, dominant frequncy in Hertz, can be hard to put into the context of a outcrop. I'll try to speak to the ideas of domain conversion and scale in a new post for later this week.

March 14, 2011 | evan