Enhancing complexity of the created fracture geometry is the primary challenge for hydraulic fracturing treatment design in shale formations because of their stress anisotropy. Therefore, near-wellbore diversion is required to evenly stimulate all perforated clusters while far-field diversion inside the created fracture induces additional branch fracturing by overcoming the stresses holding the natural fractures closed. Solid particles with different shapes and sizes are widely used as diverting agents during fracture treatments. The recommended particles should temporarily bridge inside the fracture to create a temporary low-permeability pack that increases the pressure within the fracture and enables redirection of next-stage fluid to under-stimulated intervals. The objective of this study is to experimentally investigate and optimize parameters affecting the selection of solid particles as diversion agents such as material chemistry, particle size, particle shape, particle size distribution, particle loading, carrier fluid type, and carrier fluid viscosity. Three tests were performed in this study: Bridging tests to determine the optimized particle size and loading as function of fracture width (0.04 to 0.2 in.); pack permeability tests to optimize the particle size distribution and shape needed to minimize fracture conductivity and build the needed pressure; and dissolution tests under static and dynamic conditions to determine the time need to dissolve the particles as function of temperature, rate, particle size, carrier and produced fluid. At both static and dynamic conditions, the tested solid diverters will dissolve in an aqueous solution with temperature and time. However, temperature has a more significant effect than time on the dissolution rate. For Diverter A, Increasing the water salinity reduced the dissolution of Diverter A. However, water salinity did not affect dissolution until a certain amount of solid was dissolved into solution. Dissolution was increased by reducing the particle size (and therefore increasing particle surface area). Live and spent HCl acid dissolve significantly less Diverter A than Deionized water (DI water) or Potassium chloride (KCl) solution. For Diverter B (10/30), DI water dissolved 0.06 ppg (14.2% dissolution) of Diverter B after 24 hrs. However, increasing the temperature to 225 and 250 °F, increased the dissolution to 28.7%, and 95.7%, respectively. Finally, at 300°F, 100% dissolution was noted for Diverter B after 8 hrs. Diverter B dissolves in 3 wt% KCl solution very similarly to dissolution in DI water. This gives indication that above 225°F, the dissolution of Diverter B is independent of water salinity. Hydrochloric acid (HCl acid) significantly increases the dissolution of Divert B (10/30) and (20/70), taking only 4 hrs for completely dissolution (100%). Also, the dissolution rate in live 15wt% of HCl was independent of particle size. The ratio between the fracture width and the average particle size needed to bridge was found to be 2.4. Diverters A and B tested in this study were able to bridge inside a fracture, reducing its conductivity by converting the open width into a porous medium with a tight permeability for both applications: far-field (FF) and near-wellbore (NW). Diverter A (NW) is more efficient and effective than commodity field grade benzoic acid flakes for a simulated near-wellbore application with a fracture width of 0.2 in. The diverter pack dissolved more slowly in slickwater fluid than in DI water, probably more due to the slickwater's polymer content than its minimal increase in viscosity.

Well stimulation fluids have been shown to improve oil and gas well productivity in both conventional and unconventional formations. Many formations contain multiple producing zones and areas of high and low permeability; therefore, during stimulation treatments, creating and increasing conductivity networks is highly desired. The most traditional method to increase conductivity networks is by diverting well stimulation fluids from high-permeability zones to low-permeability zones. This can be achieved by using various types of materials and techniques such as forming a filter cake that blocks off the high-permeability zone so that the fluid can be redirected to low-permeability zones. A more innovative approach is to use a diverter system made of dissolvable agents with proppants to force flow to the high-resistance path instead of the low-resistance path. The two types of particles are mixed in a way that they block any permeability from high-permeability zone once placed, effectively creating diversion of the fracturing fluid to other areas. Once the agent has provided its benefits and has dissolved, it leaves behind a proppant pack in both the lowand high-permeability zones, providing conductivity that is not otherwise achieveable. The fracture geometry is consequently enhanced by ensuring that the fluid and proppant are able to access all available fracture networks and open perforations. This paper describes an evaluation of two biodegradable particles and their application as diverters and also in combination with proppants for diversion. Conductivity studies were performed to determine regained conductivity under stress and temperature. The dissolution profiles of two soluble particles and comparison with polylactic acid were also performed in static conditions as function of time, size and type of carrier fluid for individual particles as well as their mixtures with proppant. The conductivity studies showed that once the dissolvable particles dissolved, the proppant pack provides conductivity that is orders of magnitude higher than when only the biodegradable particles are used for diversion. The studies also show that a material with glass transition temperature below the application temperature had better strength for high-temperature application, and each material has a dissolution profile that is a function of the particle size distribution and temperature.