Significant future reserve additions in the Permian Basin of West Texas and Southeastern New Mexico will come about through improved oil recovery techniques (IOR) applied to existing reservoirs. The major companies have an impressive list of improved or enhanced recovery projects on their strategic lists. On the other side of the street, independents are competing to acquire the major's non-strategical properties that are judged to have IOR potential. The Permian Basin is certainly one of the world's most mature producing provinces, but it is also a frontier for advanced IOR technology.

Primary development of the world class Permian Age producing horizons in the Permian Basin occurred from the mid- 1930's through the 1950's. The 1960's was the era of secondary recovery with the establishment of many of the Basin's water injection projects. A majority of these waterflood projects were probably based on the "Tank Model" concept of a reservoir, involving little or no geologic input. The fallout from the initial failure of some of these projects started industry on the road to developing a joint geological/engineering approach. One of the earlier papers to appear in engineering literature discussing the geological aspects was Dowling's 1970 paper titled "Application of Carbonate Environmental Concepts to Secondary Recovery Projects(1). A recent contribution in this area is a 1991 SPE Paper by Holtz, Ruppel and Hocott with the Bureau of Economic Geology at the University of Texas(2). Reading these two papers together shows the advances in carbonate geology and it's application to reservoir exploitation.

On the engineering side, much of the emphasis has been infill drilling. A 1974 paper by Driscoll listed nine factors that influence additional recovery through infill drilling(4). In 1976, Stiles authored a paper on optimizing waterflood recovery in the Clearfork(4). This was the first of several papers by Stiles and his colleagues at Exxon that has served as the foundation for the technology that has evolved into reservoir characterization. A good summary of what has been accomplished through infill drilling and reservoir characterization in West Texas carbonates is contained in a 1991 article by Wu 

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