Acid-Fracturing Treatment: A Surface-Topography Analysis of Acid-Etched Fractures To Determine Residual Conductivity

Abstract

Summary A fracture-acidizing treatment of carbonate formations can be considered successful when a relatively good fracture conductivity remains after treatment. To reach such a goal, an uneven etching of the fracture by acid is expected, so that channels are created that hydraulically maintain the fracture open, once the pressure is released after the job, and thus enhance productivity. Residual conductivity is the consequence of uneven etching of the surface, but the way this etching occurs in the field is not well understood and, therefore, poorly described. We, thus, propose, in this paper, an experimental methodology to investigate and characterize quantitatively how acid injection conditions affect the fracture surfaces, how the created rough surface is able to support the stress, and, finally, how fracture conductivity can be estimated from the surface topography. The statistical investigation of surface topography associated with acidizing experiments proposed in this paper, provides a new and interesting method for designing an acid fracturing job. It can be used as an aid to select the best fluid formulation and flow rate for a given formation type and well conditions and to forecast the behavior of the fracture after the treatment.