Fracture Conductivity with Application of 3D Printing Technology

Abstract Fracture conductivity is a measure of the success of completion designs and subsurface fracturing treatments from fractured well performance. Conductivity can be evaluated from experimental investigation. Traditionally, samples for conductivity experiments involve fracturing downhole or outcrop rocks to create realistic fracture surfaces capturing diverse morphologies. Previous studies show that fracture topography strongly influences the conductivity created, and therefore fractured well performance. However, the distinctive nature of these surfaces hinders repeatability and complicates the identification of rock characteristics impact on conductivity. In this research we use 3D printing technology to generate repeatable conductivity test samples with statistically controlled parameters to characterize fracture surface roughness and rock geomechanical properties. The test procedure provides a more isolated evaluation of the factors that control the resultant conductivity. A digital fracture surface model was generated using Geostatistical Software Library with application of mean deviation, standard deviation, and correlation lengths as changing parameters that influence surface roughness. Two mirror sides of fracture sample were made digitally as replica of original fracture samples. Molds of samples were printed with a Liquid Crystal Display (LCD) Ultra-Violet 3D printer using a selected 3D printing resin. Then the testing samples are made with cement that has appropriate mechanical properties from the molds. Several physical samples of fracture conductivity test were created with cement and the printed molds. All samples have the standard API conductivity dimension, and the conductivity tests follow the modified API conductivity test procedures. The proppant used in the tests include local 100-mesh sand and 200-mesh sand. The experimental results show a good repeatability of the 3D printed samples, which confirms the consistency of the experimental procedure. From that point, the comparisons of different proppant type, size and concentration on conductivity are made, and conclusions on proppant selection for optimal conductivity are generated. The procedure developed in this research eliminates the uncertainty of randomness of individual fractured rocks, and better evaluates the effect of the type and size of proppant on fracture conductivity for different fracture surface topographies. The finding of this research help to understand fracture conductivity as a function of geostatistical features of the fracture surface, and the effect of proppant type, size and loading on fracture conductivity and fractured well performance. This can be used in fracture designs for more efficient treatments.