huangyhg

calcs underlying genfit
i did a project a few years ago for my former employeer where i was trying to predict reservoir pressure for a gas well from a set of hourly pressure build-up data. i found that for a specific gas reservoirfff"> if i had 48 data points then i could use the mathcad genfit routine to fit the constants into the equation:
p(bar) = a*ln(hours+b)+c
the "a" "b" and "c" values were different for each well and i was able to "prove" to an acceptable level of confidence that this particular reservoir would have average reservoir pressure at the wellbore within 5 years (call it 40,000 hours) and that the data from the first 48 hours of a buildup would define the equation that allowed prediction of the current reservoir pressure.
now my former employer is a customer and wants me to write a program for their production techs to use to get the constants for each well (this is a pressure-vessel over-pressure protection exercise not a reserves study). they don't want me to use odbc calls to mathcad so i'm in a position of writing a vba version of genfit. does anyone have any good links to the theoretical basis for genfit? i've done some searches and haven't yet been able to find a curve fitting theorm that uses partial derivatives like genfit does.
david
check out our whitepaper library.
is genfit the same as a gaussian fit?
if so, this document refers to a gnu scientific library with such a function, and the link in the document should take you to the source code used in the library:
thank you, i thought that a gausian fit only applied to a straight line, i was apparently wrong. the first document had everything i needed.
david

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