A.D.Hill
and D.Zhu, University of Texas at Austin,
SPE Members

Paper presented at the SPE Annual Technical Conference and Exhibition held in New Orleans, LA, U.S.A., 25-28 September 1994

ABSTRACT

Real-time monitoring of the injection rate and pressure during matrix acidizing provides operators a means to determine the changing skin factor as stimulation proceeds. Current methods are based either on the assumption of stead-state flow in the region around the wellbore affected by acid injection or on computer solution of the transient flow equations describing the unsteady reservoir flow process occurring during acidization. In this paper, a new method for real-time monitoring of matrix acidizing, the inverse injectivity versus superposition time function plot, is presented This new method can be applied with a spreadsheet computer program or a programmable calculator and accounts for the transient flow effects occurring during matrix acidizing at multiple rates and injection pressures. The evolving skin factor during a matrix treatment is readily obtained from the diagnostic plot. Hypothetical examples show how the inverse injectivity plot can be used to assess the efficiency of stimulation and diversion. Comparisons with previously presented field cases show the new method to be a simple and accurate means of monitoring the evolving skin factor during matrix acidizing.