I need simple relations for calculating "pore pressure", "breakout point", "mud lost" and "breakdown point" to produce mud weight window in Excel software. Can anyone provide articles or published materials?
There are not really 'simple' solutions. As Leydy said, you can use Eaton to predict PP with resistivity or sonic logs - but this should be done with caution and validated against actual PP observations. Overburden gradient can be derived from density logs and from sonic velocity measurements if you use a sonic to density transform (e.g. Gardner). The easiest method to estimate fracture gradient (for losses) is Matthews and Kelly effective stress ration, but you need to be cautios about using this in anywhere that has high stress magnitudes (e.g. tectonically active zones). Alternatively, you can use a log-based poroelastic method, but this is a lot more complicated.
In order to calculate breakout formation, you can use the Kirsch equations (easy if the well is vertical, if not, you they are harder, see Peska and Zoback, 1995 or the Zoback 2007 textbook). However, you will need an estimate for the maximum horizontal stress magnitude, and this is a significant challenge that requires in-depth analysis.
Good luck!
Mark
For pore pressure calculation Goes to Eaton method, you will need Sonic log from drilling and density log. Breakout point, you have to interpret data from caliper log or from image logs. Mud lost, drilling reports say when the borehole has lost of circulation.
Thanks for your nice and complete answer. Could you please forward me a paper as a reference?
Luck
There are not really 'simple' solutions. As Leydy said, you can use Eaton to predict PP with resistivity or sonic logs - but this should be done with caution and validated against actual PP observations. Overburden gradient can be derived from density logs and from sonic velocity measurements if you use a sonic to density transform (e.g. Gardner). The easiest method to estimate fracture gradient (for losses) is Matthews and Kelly effective stress ration, but you need to be cautios about using this in anywhere that has high stress magnitudes (e.g. tectonically active zones). Alternatively, you can use a log-based poroelastic method, but this is a lot more complicated.
In order to calculate breakout formation, you can use the Kirsch equations (easy if the well is vertical, if not, you they are harder, see Peska and Zoback, 1995 or the Zoback 2007 textbook). However, you will need an estimate for the maximum horizontal stress magnitude, and this is a significant challenge that requires in-depth analysis.
Good luck!
Mark
I can say that you can use Eaton's method for pore pressure prediction. As Mark says, you must be careful when you use it. Eaton's exponent might be different in some regions. Therefore, you will need to adjust Eaton's exponent for your specific region. In addition to this, you need to have reliable normal trend line. There is also another useful method for PPP which is Bowers method. I usually use mud weight used to drill a well as PP to find exponent. In order to estimate fracture gradient, I can say that Eaton's fracture gradient calculation is useful, but you will need poisson's ratio values.
This is a manual with information about drilling procedures. I hope this can help you.
Regards.
Check this procedure I wrote in my master thesis which was originally taken from Hussain Rabia book "Well engineering and Construction"
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