Overpressure for Dummies

pressure/depth relationship

In our search for freelancing fools here at the Antisocial Network, we've noticed that one of the easiest ways to spot a bullshitting writer is to see just how badly he or she reworded the definition of any unfamiliar terminology. Technical terms (words that j-school grads call "jargon") are especially likely to be the victim of so-called rogeting as a freelancer without the slightest clue attempts to spin an authoritative definition. Today's example comes from eHow.com (no surprise there) where Jean Asta took a stab at "How to Calculate Overpressure"¹ and missed. Badly.

We say "missed" because Jean clearly had no idea what she was talking about, as is readily apparent from her daffynition of "overpressure":

"Overpressure is the term given to the difference in pressure measurements between the environment under normal circumstances and the pressure created in two different situations: geographic stria compressed over time and the air pressure difference caused by explosion shock waves. It's important to calculate overpressure in the first situation to drill safely into the ground and, in the second situation, to know how far a blast's impact will carry."

Jean started by conflating geologic overpressure (the bad actor that caused the Deepwater Horizon blowout and explosion) with blast overpressure; two wildly disparate situations. That's not to mention that there's no such thing as "geographic stria" – we think she meant "geologic strata," though we aren't certain. Moving on... Asta told us to use Weibull's formula to calculate overpressure. Perhaps that works for explosions (we don't have an explosives expert on staff). but it has squat to do with geologic overpressure. Which is why we were taken aback by Jean's mention of "drilling" in her instructions: "Divide the net explosive mass by the volume of the area to be drilled or impacted by the explosion."

Huh? "[The] area to be drilled"? If Jean insisted on bringing geologic overpressure and drilling into the discussion, she needed to provide a proper definition, such as this one we found in the Schlumberger Oilfield Glossary:

"Subsurface pressure that is abnormally high, exceeding hydrostatic pressure at a given depth."

That definition suggests that all one need do to calculate geologic overpressure is to measure the observed pressure and subtract the expected lithostatic pressure at the target depth.

"Overpressure" used in that sense has nothing whatsoever to do with Weibull's formula; and Asta's ignorant attempt to suggest that it does is a classic example of the quality of research performed by our Dumbass of the Day recipients.

¹ The original has was first moved and then deleted by Leaf Group, but you can still see it using the Wayback machine at archive.org. The URL was ehow.com/how_7634491_calculate-overpressure.html

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