A Quarter Century of Progress in the Application of Reservoir Engineering
Authors: Richardson J.G. , Stone H.L. 
Published: December 2007

A quarter century ago, conformance of 50 to 70 percent was the best we could do in matching reservoir behavior and calculated behavior. Now, thanks to modern tools and technology, conformance often exceeds 90 percent. Much of that progress can be attributed to the technological percent. Much of that progress can be attributed to the technological exchange fostered by the publications of SPE-AIME.

Introduction
This paper focuses attention on investigations that represent milestones in the advance of technology in reservoir engineering during the last 25 years. Our main criteria for selecting these investigations are thatthey developed new concepts and understanding orthey presented new or much-improved methods of calculating reservoir behavior.
Most of these papers have been standard references and have stood papers have been standard references and have stood the test of time. The vast majority of the reservoir engineering principles we use today were developed in the 1930's principles we use today were developed in the 1930's by the classic work of Muskat, Hurst, Schilthuis, Buckley, Leverett, and others. Muskat's work ran the gamut from describing the principles of unsteady-state behavior of aquifers to calculating pattern efficiencies in waterflooding to predicting pattern efficiencies in waterflooding to predicting the behavior of dissolved-gas-drive reservoirs. Hurst's work on unsteady-state behavior of aquifers was published before that of Muskat. Schilthuis was the first to recognize the role of connate water in calculating reserves and gave a solid basis to material-balance calculations. Leverett and Buckley and Leverett provided the basis for understanding and predicting the displacement of oil from porous media by gas or water. Thus we would characterize the 20-year period before the birth of the Journal of Petroleum Technology as an age of discovery of reservoir engineering principles. The last quarter century, spanning the life of JPT, has been an age of application of these principles. Certainly JPT has been the main forum through which we have learned how to apply these principles in increasing oil recovery and conserving our resources. As methods of calculating reservoir behavior have advanced, so has the need for detailed knowledge of the properties of specific reservoirs. Numerous papers appeared in the early 1950's on methods of papers appeared in the early 1950's on methods of measuring relative-permeability and capillary-pressure/ saturation relations on small core samples. General agreement was reached as to methods for measuring the two-phase flow relationships for gas/oil systems. But because of the complex wetting characteristics of some reservoir rocks, no consensus has yet been reached within the industry for a standard way of measuring the water/oil flow characteristic of reservoir rocks. However, many laboratories advocate the use of carefully preserved core samples in water/oil flow tests. preserved core samples in water/oil flow tests. The advent of reservoir simulators also required more detailed knowledge of reservoir properties, particularly the distribution of permeability and porosity. particularly the distribution of permeability and porosity. Before simulators became available, the method of Stiles, was often used to approximate behavior in a heterogeneous system. Stiles paper, "Use of Permeability Distribution in Waterflood Calculations," Permeability Distribution in Waterflood Calculations," advocated the use of a cumulative-flow-capacity/ cumulative-thickness plot derived from core data to characterize a formation.
JPT
P. 1371