Economic Aspects of Application of Computers to Reservoir Engineering
Authors: Irby T.L. , Arps Irene H. 
Published: December 2007

Abstract
A brief history of the development of computer utilization for reservoir engineering problems is traced from the use of card machines in 1948 through the large scale digital computers in 1964. During this time the capacity and speed of digital computers have increased by several orders of magnitude. Along with the development of numerical techniques and programming languages, this has led to a constantly increasing use of machines by engineers, and there appear to be no practical problems in reservoir engineering that cannot be solved with a computer. The only question remaining today about the practical application is that of economics. This paper summarizes the present scope of computer applications in reservoir engineering, the significant factors contributing to the economics of both simple and complicated applications to petroleum reservoirs, and includes a review of past trends and forecasts of future developments in this field.
Introduction
From the general advent of punch card machines, in about 1948, through the development of the large scale computers now available, the growth in usage of these machines by reservoir engineers has kept pace with the machine development. The first machines were difficult to program, requiring instructions through an especially wired board for each calculation. They were of small capacity and consequently limited to relatively simple calculations, as well as being extremely expensive compared to present machines in cost per calculation. Also, through about 1958, the machines were designed primarily for accounting procedures, which consist of performing relatively simple but repetitious operations on a large amount of input data. Engineering calculations, however, involve performing a large number of more complicated operations on a relatively small amount of input data, and require machines with sufficient memory capacity 10 store intermediate answers. The large machines now available have to some degree solved the problem of limited capacity. Programming methods have advanced to a simple language easily learned by engineers so that providing instructions to the machine has become less difficult and time-consuming. An engineer can now write his own programs, eliminating the cost of lost time incurred by giving instructions to a programmer who knows the machine but not the problem. From a theoretical viewpoint, the art of application of digital computing machines to obtain solutions of the differential equations describing reservoir behavior was well established by the mid-1950's The most advanced applications to reservoir engineering now consist of the large unsteady-state, multiphase, two - dimensional numerical reservoir models. Use of machines for flash calculations, simple material balances, statistical analysis of reservoir data and other similar problems have become almost routine. Widespread usage of computer applications is in itself proof of their economic advantages, but the exaggerated idea of computing costs that was instilled quite early in the minds of engineers and management still lingers, primarily in the minds of non-users, and is a barrier to full reservoir engineering utilization of the present day machine capabilities. The economic attractiveness of machine usage has increased steadily over the past 16 year development period, and there is every reason to believe this trend will continue. Larger capacity machines, improved techniques and more universal understanding of proper usage will lead to the establishment of an integrated system of computer programs for engineering problems which will be used in a routine manner for the optimization of oil and gas field exploitation. It should be emphasized that the use of computer technology in reservoir engineering does not eliminate or supplant the reservoir engineer.
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