The recent success of coiled tubing fracturing in shallow wells has increased interest in using coiled tubing for fracturing deeper and hotter wells. Industry efforts need to now focus on understanding what properties of a fracturing fluid are required to successfully carry proppant at high rates through the coiled tubing, fracports, perforations and into these deeper formations. The key performance requirements of a coiled tubing fracturing fluid for deeper wells are low friction pressure and adequate proppant-carrying capability after exposure to high shear zones and higher temperatures.

This paper summarizes the results of pilot and field scale testing that led to the development of an optimized coiled tubing fracturing fluid. Results show that polymer-based fracturing fluids can be controllably delayed to have low friction pressure through the curved coiled tubing unit and straight tubing. However, results also show that fluid stability can be significantly reduced when pumped through small diameter tubing followed by high shear zones such as fracports and then perforations. Results demonstrate that correct fluid choice and fluid optimization are required to meet proppant transport requirements. For coiled tubing fracturing to be successful, the fluid and treatment design recommendations should balance the friction pressure limitations with the fluid stability limitations.

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