Fracture Hydraulic Conductivity Estimation From Borehole Stoneley Wave Transmission And Reflection Data

Permeable fractures in reservoirs are important structures in the exploration and production of hydrocarbons, and hydraulic conductivity is of primary importance in the characterization of fractures. The hydraulic conductivity is defined as ?0H/?, which is integrated fluid mobility (ratio of permeability ?0??to viscosity ?,) over a fracture zone of thickness H. A method for data processing and analysis is developed that obtains the conductivity of borehole fractures from array acoustic waveform data containing low-frequency Stoneley waves. This method consists of three major procedures: wave separation,. wave modeling, and fracture hydraulic conductivity estimation. The first procedure separates Stoneley waves into transmitted and reflected wavefields. The second procedure corrects the effects of borehole irregularity (e.g.. enlargement, washout, etc.) on the Stoneley waves; it accomplishes this by using caliper and Stoneley slowness logs to numerically model Stoneley wave propagation. The final procedure uses both the measured and synthetic Stoneley wave transmission and reflection data to estimate the fracture?s hydraulic conductivity. A theory for Stoneley wave propagation across fractures and washouts is used in the estimation. In this new technique, the correction for borehole irregularity removes the effects unrelated to fracture permeability. and the use of both transmission and reflection data constrains the estimation to yield valid conductivity values, so that the process is effective in assessing borehole fracture fluid-transport properties from Stoneley wave data.