Design and Operation of a Laboratory Model to Study Unsteady-State Radial Gas Flow in Porous Media
Authors: Evers John F. , Dempsy John R. , Preston Floyd W. , Swift George W. 
Published: December 2007

Evers, John F., Student Member AIME, U. of Kansas, Lawrence, Kansas Dempsy, John R., Member AIME, U. of Texas, Austin, Texas Preston, Floyd W., Member AIME, U. of Preston, Floyd W., Member AIME, U. of Kansas, Lawrence, Kansas Swift, George W., Member AIME, U. of Kansas, Lawrence, Kansas

Abstract
This paper reports on the development of an experimental model which simulates the production of gas from a reservoir. The model is comprised of a cylinder of reinforced Portland cement which is two feet in diameter and six inches in height. It is fitted with a production well at the center and 32 observation wells—eight logarithmically spaced on each of four mutually perpendicular azimuths. All wells are 0.014 inches in diameter and are completed (open hole) through the thickness of the cylinder. The measured porosity of the model is 0.146 and the apparent permeability is in the range of 25–100 microdarcies. These properties are such that a 20 year production history properties are such that a 20 year production history of a field reservoir drilled on 640 acre spacing can be simulated in approximately 9 hours, giving a time scaling factor between the model and its field counterpart of 1:20,000. Data are presented showing a drawdown and a buildup test, presented showing a drawdown and a buildup test, the variation of permeability with distance from the producing well, and the effect of incomplete pressure buildup on the estimation of gas pressure buildup on the estimation of gas reserves. Since the model only recently become operational, data analysis on the runs made to date has not yet been completed. However, the data presented in this paper demonstrate the feasibility presented in this paper demonstrate the feasibility of experimentally modelling gas flow in porous media. This type of experimentation will allow fuller understanding of the mechanisms of gas flow in reservoir geometries. The described modelling technique opens broad vistas for experimentally studying conventional, interference, and pulse testing method, multiple well production phenomena, retrograde effects on permeabilities phenomena, retrograde effects on permeabilities near the producing well, etc.

Introduction
A long term deliverability prediction for a gas well is generally based on data determined from flow tests that are of short duration relative to the producing life of the well. These data form the basis for establishing the parameters of a mathematical model used to predict performance at future times. Since the results obtained from such a model represent only a theoretical interpretation of the physical process occurring, experimental verification under carefully controlled conditions from discovery to abandonment is needed. Ideally, one might consider such an experiment to be conducted in the field. Even if the cost could be justified, the time required would be prohibitive. Thus an experimental model would be desirable if the scaling of pertinent parameters, e.g., time, is properly treated. parameters, e.g., time, is properly treated.