Steam injection EOR began in California forty years ago, and has been highly successful. As a consequence, California's thermal recovery operations represent a leading source of EOR production in the world.

The understanding of most early thermal recovery operators was limited to the concept of "heat reduces heavy oil viscosity, and reduced viscosity means more production." Steam injection was attempted in almost any reservoir having viscous oil with little appreciation of other recovery process considerations. Although several early pilot projects were steamfloods, most early applications were cyclic stimulation. During the late 1970's, steamflooding became predominant, and many people considered steamflooding to be a displacement process (hence the term "steam drive’). With this paradigm and high oil prices, there was little impetus to understand efficient use of heat. The predominant philosophy was "If you want more oil, inject more steam." With the later collapse of oil prices, operators returned to review process fundamentals and to determine how to more efficiently operate steam projects. This paper discusses the shift to an override, or gravity drainage, model concept. This helped lead to reduced steam injection and improved thermal efficiency through the use of heat management. This paper discusses the shift to the concept of steam override and gravity drainage as steamflood recovery mechanisms and the subsequent use of heat management practices that improved thermal recovery efficiency.

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