Characterization of small scale heterogeneity to predict acid fracture performance

• A new methodology for analyzing acid fracture conductivity is presented.
• The method uses geostatistical parameters, describing small-scale heterogeneity.
• The method is tested using a case study well from the Hugoton Field.
• The results indicate a unique and more realistic conductivity prediction.

Recently developed models of the acid fracturing process have shown that the differential etching necessary to create lasting fracture conductivity is caused by the heterogeneous distributions of permeability and mineralogy along the fracture faces. To predict the conductivity that can be created by acid in a particular formation, the models require information about these formation properties and their spatial variation. This research aims to quantify the small scale heterogeneity by using a geostatistical description to ascertain the distribution of permeability in a carbonate formation. Parameters that quantify the directional correlation and variance of the data are developed. The correlation length and variance parameters are a first step in being able to couple acid transport and rock dissolution models at reservoir scale with a model of fracture conductivity based on channels and roughness features caused by small scale heterogeneity. These geostatistical parameters are developed for a well in the Hugoton Field. Data leading to their derivation are obtained from a combination of well logs and cores. The resulting geostatistical parameters and acid etched width are used to predict acid fracture performance. Application of new model conductivity correlations results in a unique prediction for the acid fracture case study that differs from the industry standard.