The role of the proppant in hydraulic fracturing is to keep open or “prop” the induced fractures. However, not all fractures propped. Determining the distribution of propped fractures is important to understand further the flow of hydrocarbons and microseismic event locations. In this study, our goal is to investigate whether any variations in the velocities of propped materials could be diagnostic of fracture fill by proppant. To undertake experiments on a known physical model, we use 3D-printing technology. We printed two models (with orthorhombic symmetry. horizontal layering and vertical cracks), one with open and originally air-filled fractures (hereafter called A model) and another with proppant-filled fractures (hereafter called the P model) and used them in our laboratory study. The density and porosity of model A are 0.763 g/cc and 24% respectively. After filling fractures with proppant, the density of model P increased to 0.822 g/cc and porosity decreased to 21%. We observed approximately 10% reduction in both P and S velocities from model A to model P. We observed 40% increase in P-wave velocity when model A saturated with water and proppant. Shear velocity further decreased by 10% when proppant added to the water saturated model. We also estimated the dimensionless orthorhombic Thomsen style P-wave anisotropic coefficients for two models to characterize the likely anisotropic behavior of the material. While we observed a negligible change in , a significant change in P-wave anisotropy is observed from +0.012 (A) to -0.041 (P). Negative ? indicates a decrease in P-wave velocity when P-wave propagates perpendicular to proppant-filled fractures. The magnitude of S-wave splitting at vertical incidence decreased by 6% from dry model A to model P. This study shows strong evidence of a difference in elastic-wave velocities and anisotropy varying with proppant. This may prove very useful for hydraulic fracture monitoring and stimulated and propped reservoir volumes.
Presentation Date: Tuesday, September 26, 2017
Start Time: 3:05 PM
Location: Exhibit Hall C/D
Presentation Type: POSTER
