Maximum Reservoir Worth - Proper Well Spacing

Abstract

Published in Petroleum Transactions, AIME, Volume 216, 1959, pages 334–340. Abstract The cost of finding and developing new reserves is continually rising. We must meet these rising costs with in ore economical operations. This can be accomplished if we revise our ideas of proper well spacing and well allowables to consider the concept of optimum well spacing. According to this concept, the optimum spacing is the one which leads to the maximum present worth for a reservoir when all factors affecting total cost and total revenue are considered and when the wells are produced in the most efficient manner. Application of this principle efficiently utilizes available well potential and properly considers the recovery efficiency in addition to fixing the spacing on the basis of the amount and value of the oil to be recovered. This study presents an analysis of one producing zone containing low gravity crude to illustrate the effect of these factors on the present worth and on the optimum economic spacing under two production drives-evolved gas and water drive. The maximum present worth occurs when the optimum number of wells for open-flow operation is employed. Frequently, this optimum development calls for very wide spacing and the ideal field rates are not unreasonable. Under other circumstances where proration is necessary, an optimum combination of well spacing and well allowable exists which permits production at relatively high rates. The optimum well density in a field depends on the recovery efficiency and the value of the oil. In solution gas-driven reservoirs this optimum spacing for operation at high producing rates can vary from extremely wide spacing to handle viscous low gravity oil in thin formations to relatively close spacing in thick sands where good recoveries are expected. Because of the better recovery from water-driven fields, the optimum spacing in these fields is closer than in solution gas-driven fields. Also, the water encroachment pattern is dependent upon the well spacing, and an adequate number of wells is needed to assure a good sweep efficiency. The economic optimum well density in a water-driven field is high enough for this purpose.