This paper presents a delayed fracturing stimulation fluid system designed to delay crosslink time and reduce surface pressure by reducing pipe friction during pumping to achieve improved recovery of heavy oil where preheated treatment fluids are required.

The new approach is based on the chelating properties of delaying agents. The delayed stimulation fluid system includes guar and a boron-based crosslinker. The base stimulation fluid was preheated to 167°F (75°C) before pumping, Without adding the delaying agent, crosslinking occurred at surface conditions such that high tubular friction pressure was experienced while pumping the stimulation fluid down hole. To measure the crosslinking time, vortex closure time was observed. The delay in crosslinking time was directly proportional to the vortex closure time. A significant change was observed in the vortex closure time after adding the delaying agent to the heated fluid.

The novelty of the fluid system delaying agent is in its ability to allow pumping heated borate-crosslinked guar gels with crosslink-delaying efficiency, resulting in reduced surface pressure and adequate fluid viscosity in the formation.

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