Experimental Study of Self-Degrading Diverting Agent Particles Used for Improving Hydraulic Fracture Placement

Abstract

Fluid placement is essential to obtain a successful stimulation treatment. Formation heterogeneity, varying stress distribution among formations and irregular fluid injectivity via perforations may lead to uneven fracture propagation along the formation net thickness. Isolation techniques provide solutions to such issues and can range from using mechanical restrictions that redirect the fluid flow, up to the use of specially designed particles placed in the flow stream to divert the treatment. Mechanical methods can include packers, bridge plugs and sand plugs which are used to mechanically separate the stimulation process into multiple stages pumped along the wellbore path. Ball sealers are part of the same category, designed to seal individual perforations during the pumping process and completely isolate a section of the wellbore to divert the injected fluid to subsequent zones. Another method that is widely used in large pay zones is coiled tubing in which accurate frac generation and fracture growth adjustments can be monitored in real time. Non-mechanical isolation designs consist of soluble or insoluble particles, with different sizes and compositions, mixed within the stimulation fluid that accumulate at the wellbore wall to form a low permeability cake, forcing fluid flow into areas with lower injectivity. Such particles are known as diverting agents and dissolve as a function of temperature and type of the injected or produced fluids. The study presents the main isolation techniques used during multi-stage fracturing operations and the laboratory investigation results affecting the selection of solid diversion agents such as material chemistry, particle size, particle shape, particle size distribution, temperature and type of carrier fluid.