NEW PRESSURE ANALYSIS TECHNIQUE USING REPEAT FORMATION TESTER DATA

Abstract

Current practice is to derive permeability from the pretest of wireline formation testers by the conventional Horner plot method. The major drawback of this type of analysis is the reliability of the flow time and flow rate estimates.A new technique to derive permeability from pressure response during the sampling period has been developed. The new method is based on the principle that at the end of the sampling period the volume of the fluid in the chamber is equal to the nominal volume of the sample chamber.The suggested method applies the approximation of the continuous pressure decline by a series of pressure steps as applied for water influx calculations.In its present form the technique has limitations due to flow regime shapes, number of phases present and the degree of formation damage.Research is underway to find acceptable solutions for the stated limitations.