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Unformatted text preview: ariables required to
calculated the approximate pressures at
which a formation will fracture are (1)
depth of the zone of interest, (2)
formation fluid pressure within the zone,
(3) the rock type.
133 2. Fracture Gradients in Deep
Fracture gradients in deep waters are
generally lower than those at equal depths
on land operations. The example problem
provided in this section will explain the
application of this procedure. 134 Copyright(c) 2005 by Ali Ghalambor & Boyun Guo 67 Problem: in the illustration on Fig.1, what is the effective
fracture gradient at the casing seat?
Solution:Step1: Convert water depth to equivalent section of
from the overburden stress chart, at 4000 ft the overburden
stress gradient 0.89 psi/ft
Step2: calculate and convert apparent fracture gradient to
actual fracture gradient:
522 ft +3000 ft=3522 ft
Fracture gradient at 3522 ft(From chart)
=13.91 ppg+ .3 ppg=14.2 ppg
Therefore, fracture pressu...
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- Fall '14