In the past decade, with the widespread commercialization of the shale plays, there is an increasing demand on the fracturing industry. Thus, it becomes important to understand and optimize the amount of horsepower and the fracturing fluids necessary for a fracturing job. We present, laboratory hydraulic fracturing experiments on Indiana limestone and Lyons sandstone using two different viscosity fluids (60 cP and 1000 cP oil). A uniaxial horizontal stress of 1000 psi was applied to control the fracture direction. The main objective is to understand the effect of fluid viscosities on hydraulic fracture propagation. We used the two techniques: microseismicity, to monitor the fracture propagation and scanning electron microscopy (SEM), to understand the fracture morphology. Spatial and temporal propagation of the fracture is observed along the maximum stress direction. Shear type fracture mechanisms are found to dominate. Lower pressurization rates and higher breakdown pressures are noted when 1000 cP oil is used. A fracture trace is visible on the plugs recovered in the fractured zone defined by the microseismic event locations. Thicker cracks are evident corresponding to increase in cumulative number of events recorded. SEM observations confirm the wider aperture at the injection point and the frequent occurrence of the terminations and bifurcations farther along the fracture front.
With the increasing interest in shale gas, shale oil and tight sand reservoirs, microseismic monitoring of the hydraulic fractures has become a common practice. The increase in the horizontal lateral lengths and the number of fracture stages increased the demand for seismic monitoring further. The multistage hydraulic fracturing costs can account to as much as 25% - 35% of the well costs. Optimization of horsepower and amount of frac fluids used is required for economic hydraulic fracturing. The main constituent of any fracturing fluid (>95%) is water.
