Case Study 6 - Solutions

# The first line with the smaller slope represents the

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Unformatted text preview: ed Horner straight line. This line will remain straight provided the assumption of semi-infinitely acting remains valid over the time period ∆t. Note the initial curvature, towards the right side of the plot, represents wellbore storage effects during early times. The nature of the Horner ratio makes small values of time begin on the right and move left as time increases. This line does not approach the initial reservoir pressure ( ) given as 3460 psi. Therefore from this we can assert this must be the shifted Horner straight line, since an un-shifted Horner straight line for an infinitely acting reservoir would intercept at a Horner ratio of 1. As a result this leads to the conclusion of a nearby fault. The second line (imposed on the straight line region to the left during later times) has exactly twice the slope of the first line. This has physical significance, since a reservoir must approach the initial pressure provided fluids continue to fill as a result of unbalanced pressures. Mathematically, this can be shown as 12 fact through the assumption of case study. at large values of ∆t. This was shown is step 6 of this Using the traditional buildup procedures the permeability and skin can be determined. The slope of the Horner shifted straight line can be easily calculated from a simple rise over log (run) on the plot. Once this is known the reservoir permeability can be calculated from the following equation. Horner Plot - Case Study 6 3550 3500 pw 3450 3400 3350 3300 3 250 1 10 100 (t+∆t)/∆t The slope, as calculated from Horner times of 10 and 100, is: 13 1000 Entering this into the slope properties equation: In order to determine skin we must look at the flowing period prior to shut-in. Specifically, we look at the wellbore pressure at the end of the flow period and evaluate our infinitely acting reservoir drawdown equation. This is given by, in SI units: This can be expanded, altered with the buildup formulation and changed to field units and base 10 logarithms. In addition, skin is typically determined by picking a point of the H...
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## This note was uploaded on 01/26/2014 for the course ENG 9111 taught by Professor Drjohanssen during the Spring '12 term at Memorial University.

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