Analysis of Well Productivity as Related to Changes in Well Damage

Abstract

Well damage, given by the well’s skin factor, and indicated by a drop (or increase) in productivity and an increase (or decrease) in pressure drawdown, is the result of changes in reservoir properties, particularly by a reduction in formation permeability. An analysis is made of the changes in reservoir characteristics that occur during exploitation, and affect skin values. The incorporation of the “M factor” in inflow performance relationships that describe well damage effects is described. The behavior of this factor for different well damages is discussed. The change of M as a function of well skin factor is also presented. Three inflow performance relationships, two for petroleum systems and one for geothermal systems, and their main characteristics were analyzed. The calculation of well skin factors and their variation during reservoir exploitation were applied to well management decisions. The use of type-curves gives results that are consistent with the behavioral link between well productivity and damage.