The subject of reservoir energy and its efficient utilization has been wellexplored in many papers. The present effort, therefore, is limited to a summaryof existing information combined with an emphasis of the probability that therelative importance of controlling factors will change with advancingknowledge. Consequently the necessity for flexibility in laws and regulations, inherent in the problem, is emphasized.
Many terms have been widely used in the literature without having beenspecifically defined. For example, confusion exists in the use of"reservoir energy" and "gas energy." The latter is much morelimited in meaning than the former. Other terms have been variously used.Consequently, I shall preface my remarks with definitions of a few of the morepertinent terms.
Reservoir energy is that force or forces, active or potential, that is nativeto the reservoir and has the power to move oil through the reservoir rock. Theenergy may result from expanding gas, from hydrostatic head, from the weight ofoverburden, or from any other source. Gas energy is the expansive power of gaswhen pressure is reduced. It is one type of reservoir energy.
An oil reservoir is that part of a geologic formation or-formations in whichoil occurs in commercial quantities wholly surrounded by nonproductive rock.The essence of this definition is effective separation rather than remotenessand under it oil reservoirs may be superimposed in the same oil pool.Conservation of reservoir energy means primarily its maximum use in theproduction of oil.
Unit operation is a plan of development and production, which embraces anentire oil reservoir under a unity of engineering control. It is distinct fromunitization, which has to do with arrangements of organization and equities tomake unit operation possible in areas of divided ownership.
