Methods of using pressure build-up or flow tests to estimate formation permeability, formation pressure and well damage are reviewed. A number of phenomena which cause actual pressure build-up behavior to differ from the idealized case, such as the effects of boundaries, skins, inhomogeneities, partial penetration and two-phase flow, are discussed. It is concluded that the same method of analysis of build-up curves can be applied with slight modification to oil reservoirs, gas reservoirs and reservoirs producing both oil and gas. The calculations can be carried out on a form sheet, a copy of which is included in the paper. Examples are worked out for four different types of reservoirs.
Although the basic theory of pressure build-up behavior in wells was developed many years ago, important contributions since that time have extended the original applicability to a much wider variety of situations. The purpose of the present paper is to summarize the present status of pressure build-up theory and of its applicability.
The approach in this paper will be to start with the simplest type of pressure build-up curve and to show how reservoir rock properties, reservoir fluid properties and wellbore conditions tend to distort the idealized picture. Methods for taking these distortions into account and for determining values of reservoir formation properties from build-up curves will then be considered.