The elements of the oil-well-spacing problem

This paper reviews the several factors which determine the spacing of wells in planning the development of oil fields to secure the maximum economic ultimate recovery of petroleum. The physical factors controlling oil drainage are given special consideration, and the limitations of our present knowledge of their influence are pointed out. The expulsive effects of gas pressure, gravity, and edgewater pressure in causing movement of oil into wells are discussed, and quantitative experimental data are produced showing the influence of pore resistance and capillarity of oil sands and viscosity and adhesion of the oil in resisting the expulsive forces. The influence of geologic structure, of the diameter of the well, and of the depth and thickness of the productive sand on the economic interval between wells is also explained. The more important economic considerations in planning the development program-particularly the interest cost of deferred production, the cost and efficiency of production, and the future selling price of petroleum-are discussed in general terms. The fallacy of using well production records as a basis for well-spacing, without supplementary study of the more fundamental variables controlling oil drainage, is pointed out. In conclusion, the author summarizes in tabular form the qualitative effect of the several variables discussed, and suggests the necessity for a thorough technical study of the factors controlling oil drainage in order that the spacing of wells may be placed on a more scientific basis.