133 2 fracture gradients in deep water fracture

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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 Water 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 formation 1000ft×0.465 psi/ft=465psi from the overburden stress chart, at 4000 ft the overburden stress gradient 0.89 psi/ft 465psi/(0.89psi/ft)=522 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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