Visual Studies of Well Interference
Authors: Slater G.E. , Hegeman P.S. 
Published: December 2007

A reservoir simulation model was used to study thee transient behavior of a single well, a production-injection well pattern, and a pressure pulse for a single well. The results were graphically displayed in pulse for a single well. The results were graphically displayed in three-dimensional form, and a time-lapsed movie was produced to give visual insight into understanding pressure communication in a reservoir.

Introduction

Although some petroleum engineers may appear to have "divine guidance," it is doubtful that even they have ever actually seen a pressure transient move through an oil reservoir. Since most petroleum engineers must rely on indirect measurement of reservoir properties and must speculate on what really is happening "down below," the authors wondered whether some graphic material could be created that might give a better insight into how pressure transients really move around in a reservoir. The results have been quite interesting. These results are illustrated by Figs. 1 through 14, but the real insight comes from viewing a time-lapsed, animated movie showing the behavior of pressure surfaces in several "textbook" reservoirs. The movie can be obtained by SPE-AIME members from the authors.*

The Reservoir Model

A numerical, areal, slightly compressible oil reservoir simulation model was used to calculate the transient pressure behavior in several simple example reservoirs, pressure behavior in several simple example reservoirs, Actually, any existing reservoir simulation model could be adapted. Models of this type have been described many times in the literature; what is important is what was done with the voluminous data churned out by the model. Very short time steps of 0.01 to 5 days were used where appropriate to simulate a continuous process by a series of shorter, static conditions. Much experimentation was necessary before an appropriate set of time intervals could be selected for each reservoir.

The Graphic System

The spatial pressure distributions produced at discrete time intervals became the input data for a computer program that controlled the display of the data onto program that controlled the display of the data onto a cathode ray tube (CRT) using the IBM ADAGE graphics systems. The x and y axes of the surface represented the x and y grid axes of the simulation model. The z axis of the displayed surface represented the pressure at each intersection of the x-y grid lines. pressure at each intersection of the x-y grid lines. The graphics system joined the points of the three-dimensional representation by more-or-less solid lines, creating the effect of a pressure surface for each discrete time interval. Each surface was placed sequentially on the CRT and a motion picture was produced that recorded the pressure surfaces as a nearly continuously changing system. The number of frames of film taken of each discrete surface was controlled by commands inserted into the computer program using the language from the ADAGE Monitor and Operating System Image Display Operator, GRAFX. GRAFX interprets a set of image commands to produce a displayed picture on the CRT screen. In addition, special GRAFX statements can be used to rotate the displayed picture about three axes, to displace the picture, and to scale the display. GRAFX also controls the graphic input/output devices and provides for monitoring and sampling these devices.

JPT

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