Water-based gelled fracturing fluids with guar and guar derivative polymers are used for viscosity development, leakoff control, and proppant transport during hydraulic fracturing operations. After placement, the polymers' mass should be extensively degraded with breakers, such as acids, enzymes, and oxidizers, to help maximize fracture conductivity and minimize residual damaging materials. Without a mechanism to delay their activity, these types of breakers react quickly in most downhole environments, some even at low temperatures, and can degrade the fracturing fluid at an undesirable rate or too early in the treatment.

Oxidizers, such as ammonium peroxydisulfate, are widely used breakers. Oxidizer performance depends on many factors, such as time, temperature, breaker concentration, and polymer loading. Optimal breakers should generate minimum or no unbroken gel residues to help prevent formation damage or damage to the propped fracture. With wells being drilled deeper and at higher temperatures, a high-temperature encapsulated breaker is important for optimum fracturing fluid performance. The high-temperature encapsulated breaker discussed in this paper helps control gel breaking time, enables crosslinked fracturing fluid stability for a longer time than designed, and minimizes residual mass.

This paper presents a high-temperature encapsulated breaker that works at temperatures up to 330°F. The new breaker was thoroughly tested in a laboratory testing scheme that included rheology testing up to 330°F. Testing also included a comparison between the current industry oxidizer and the new high-temperature encapsulated breaker. Additionally, a high-pressure/high-temperature (HP/HT) filter press study of current fracturing fluids and the new breaker was conducted although not included here.

This study highlights the high-temperature encapsulated breaker performance when added to zirconate crosslinked fracturing fluids and compares it to a control fluid without breaker. Also reported for each case are the results from using the same oxidizer without being encapsulated for the same testing conditions.

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