Table of Contents Table of Contents
Previous Page  87 / 743 Next Page
Information
Show Menu
Previous Page 87 / 743 Next Page
Page Background

Dynamic Data Analysis – v5.12.01 - © KAPPA 1988-2017

Chapter

3 – P ressure Transient Analysis (PTA)

- p87/743

3.D.5

Pi influence on the deconvolution

In the case illustrated in the figures below, we have run a test design with a homogeneous

infinite model. So we know that the right response is homogeneous infinite. It starts from an

initial pressure of 5,000 psia. There was a 400 hours constant rate production period followed

by a 100-hours shut-in.

When the deconvolution is run with too high a value of pi (red dot), there is an additional

depletion compared to the infinite case. In order for the deconvolution to honor both the build-

up and the initial pressure, it will have to exhibit at late time an increase of the derivative

level, typical of a sealing boundary. Conversely, if we entered too low a value of pi (blue dot),

there needs to be some kind of support to produce depletion smaller than the infinite case. The

deconvolution will exhibit a dip in the late time derivative.

In other words, deconvolution honors the data of the first 100 hours of the build-up, and then

uses the flexibility of the 400 last hours to ‘bend’ in order to be compatible with the entered

value of pi. Why is the shape so smooth? Because, on top of this, the optimization process

minimizes the total curvature of the derivative curve.

Fig. 3.D.22 – Deconvolution of a single build-up with different values of pi

For an infinite reservoir - Left: Simulation; Right: extracted build-up

Fig. 3.D.23 – Deconvolution with pi too high (red) or too low (blue)