Bottom-hole Measurements in Pumping Wells

The fundamental hydrodynamic principles governing the production of oil fromwells have been carefully studied and evaluated by many investigators. Theseprior studies are quite complete and cover virtually the entire field of oilproduction and recovery. One of the most important measurements in productionstudies is that of the bottom-hole pressure at various rates of production. 2It is the purpose of this paper to outline the technique and economics offluid-level measurements as applied to pumping wells and to review brieflyother methods for obtaining bottom-hole data. The applications of bottom-hole pressure or fluid-level measurements are basedon simple hydrodynamic principles. Under equilibrium conditions,Pbh = hd + pg + pch whenPbh = bottom-hole pressure, lb. per sq. in.absolute,h = height of fluid in well, ft.d = average fluid density, lb. per sq. in. per foot,pg = weight of section of gas column 1 in. square from fluid level tocasinghead,Pch = casinghead pressure, lb. per sq. in. absolute. In words, equation 1 states that the bottom-hole pressure is equal to theweight hd of the column of fluid plus the weight of the column of gas betweenthe fluid and the casinghead plus the casinghead pressure. At moderate rates of flow, the rate of production is approximately proportionalto the difference between the reservoir, or static bottom-hole, pressure andthe flowing or producing pressure. However, at production rates approachingzero and also at high rates the proportionality may break down. T.P. 1058