Computational Fluid Dynamics (CFD) has been used as a means of accurately determining the time and displacement volume of balls used to activate multiple ports in a multi-zone fracturing system that is 18,000 feet long.

Hydraulic fracturing techniques are complex and highly evolving. In such processes, ball-operated sliding sleeves are a means to access multiple zones in the formation, creating fractures into which proppant is pumped. The success of placement in such systems depends upon accurate calculation of the time required for a ball to be pumped from the topside to the multiple ball seats over distances of tens of thousands of feet. It is vital that any treatment is not over displaced and thus accurate volume and timing is essential.

Using CFD unsteady simulations for validation, a simple mathematical model was created that allowed an accurate, quick-response evaluation of the time taken for a ball to be pumped through a completion. These simulations involved the use of Dynamic Fluid Body Interaction (DFBI), morphing and overset computational meshes as well as lagrangian particle-based physics. A number of challenges were met with innovative solutions; the completion followed a complex path and was over 18,000 ft in length, the duration of the study was very short, the fluid within which the ball was immersed was non-Newtonian and the particle-based fluid-particle interaction models used required validation.

This study brought together many applications areas including completion string design, the formation fracture process, CFD numerical methods, simulation management, external aerodynamics and CFD software development. Results of the simulations were compared to full-sized testing and field data.

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