Fracture geometry control and increased fracture complexity have been recognized to be critical factors in optimizing unconventional well completion design as well as preventing detrimental frac hits. A major challenge of far-field diversion in slickwater fracturing is ensuring transport of material to the fracture tip or secondary fracture in a low-viscosity fluid. This paper will present a novel far-field diverter system for fracturing with low-viscosity fluids to address these challenges composed of an engineered mixture of unique ultra-lightweight proppant and degradable material. Not only can the system effectively divert fracturing to control fracture geometry and enforce complexity, but will also maintain fracture conductivity.
Several types of tests were performed to determine the effectiveness and optimize the design of the far-field diverter system. First, a series of slot plugging tests were carried out to optimize diversion performance of the system by blocking fluid flow through targeted fracture widths while maintaining flow through the larger portions of a fracture. Next, the diverter was pumped through a flow apparatus to demonstrate its far-field transportability in low-viscosity fluids. Finally, conductivity of the diverter system after degradation was tested.
The new far-field diverter system was designed to create a permeability barrier at the fracture tip to contain fracture length growth as well as to be used in the middle of a stage to control growth of secondary/tertiary fractures to allow redistribution of fracturing fluid within the rock to further increase complexity. Lab tests demonstrated that by controlling the particle size of the engineered proppant and diverter mixture, the diverter system can be tailored to plug different fracture widths. Significantly, flow tests using a low-viscosity, slickwater fluid demonstrated the excellent transport properties and limited settling rate of the diverter. Finally, conductivity tests showed that by using an engineered mixture of non-degradable, ultra-lightweight proppant and degradable material, conductivity in the fracture is maintained after particle degradation, which is critical when applied in the middle of a stage to increase fracture complexity.
To the authors’ knowledge, this is the first published paper of a far-field diverter that is optimized for slickwater fracturing for both fracture geometry and complexity control. The new diverter technology overcomes the significant limitations of other available systems such as fracture closure, inadequate transport to the far field, or the requirement to use high viscosity fluids.