Well Test Analysis of a Multilayered Reservoir with Formation Crossflow


Heungjun Park







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The purpose of well test analysis is to identify the type of a reservoir and to determine the parameters of the reservoir quantitatively. This work is about the well test analysis of a multilayered reservoir with formation cross ow. The results are described in two parts.
In the first part, the effects of the reservoir parameters such as permeability, vertical permeability, skin, storage coefficient, and others such as outer boundary conditions and layering on the wellbore response, pressure and layer production rate, were investigated. Some important discoveries are:
* The wellbore response is observed in three different stages; it is identical to that of the
commingled system at early time and and to that of the homogeneous system at late time.
Transition occurs at intermediate time.
* The vertical permeability is the only parameter governing the initiation and termination of the
transition from the early time commingled system response to the late time homogeneous
system response.
* The direction of the formation cross flow is determined first by the layer permeabilities and later
by the skin factors.
* The influence of the wellbore storage effect can be minimized by using sandface flow rate from
each layer.
* The outer boundary conditions have only small effect on the wellbore response as long as the
transition terminates before the system feels the boundary.

In addition, the early time and the late time limiting forms of the wellbore response were derived and some approximations for the late time layer production rate were suggested.
In the second part, the nonlinear parameter estimation method was applied as a means to determine the layer parameters. Here, two new methods for the initial estimation of the parameter values were suggested and tested, where the early time and the late time limiting values of the layer production rate were used with the conventional pressure analysis for the average permeability and skin of the total system. Several examples including a real well test analysis were given.

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Copyright 1989, Heungjun Park: Please note that the reports and theses are copyright to their original authors. Authors have given written permission for their work to be made available here. Readers who download reports from this site should honor the copyright of the original authors and may not copy or distribute the work further without the permission of the author, Heungjun Park.

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