The technical indexes of encapsulated gel breaker for fracturing mainly include: appearance, effective content, particle size range, releasing rate, viscosity retention rate, these five technical indexes cover the basic performance parameters of the encapsulated gel breaker for fracturing, and the performance of the encapsulated gel breaker for fracturing can be judged through inspection.
1. Appearance
The appearance of encapsulated gel breaker is white or light yellow particles.
2. The effective content of encapsulated gel breaker
The effective content of the encapsulated gel breaker for fracturing refers to the percentage of the quality of the gel breaker wrapped in the capsule.
It is an important index to measure whether the content of active ingredients in the encapsulated gel breaker is sufficient. By definition, the effective content of the encapsulated gel breaker should be used as one of the denominators in the calculation of its release rate; Otherwise, it will cause the calculation result of the release rate of encapsulated gel breaker to deviate from the real value. However, in Q/SH 1025 0591-2009, there is no demand for the technical index of “effective content of encapsulated gel breaker for fracturing”, therefore, it is recommended that the standard should be added the technical index of “effective content of encapsulated gel breaker for fracturing”.
3. The particle size range of encapsulated gel breaker
Q/SH 1025 0591-2009 “Technical Conditions for encapsulated gel breaker for fracturing” stipulates that the particle size range of encapsulated gel breaker for fracturing is 0.425mm~0.850mm, it should be no less than 80%.
4. The releasing rate of encapsulated gel breaker
The release rate of encapsulated gel breaker for fracturing is the percentage of the quality of the gel breaker released by the capsule to the quality of the gel breaker wrapped in the capsule under specified conditions. At present, it is generally believed that osmotic release dominates under low pressure, extrusion release dominates under high pressure, and osmotic release also exists, but at high temperature, osmotic release is significantly intensified, and osmotic release dominates. Therefore, the pressure, temperature, soaking time, formation conditions and other factors will affect the release rate of encapsulated gel breaker.
Q/SH 1025 0591-2009 “Technical Conditions for encapsulated gel breaker for fracturing” stipulates that the release rate of encapsulated gel breaker for fracturing (30MPa) is not less than 60%.
5. The viscosity retention rate of encapsulated gel breaker
The viscosity retention rate of encapsulated gel breaker for fracturing is the ratio of the shear viscosity value of fracturing fluid with a certain amount of samples added to the shear viscosity value of fracturing fluid without samples under certain test conditions. It is an important technical index for indoor simulation investigation of the effect of encapsulated gel breaker on the rheological properties and sand carrying properties of fracturing fluid during fracturing construction, and has certain guiding significance for determining the dosage of encapsulated gel breaker in fracturing site construction.
The main factors affecting the viscosity retention rate of encapsulated gel breaker for fracturing are test temperature, dosage of encapsulated gel breaker, shear rate and shear time. Q/SH1025 0591-2009 “Technical Conditions for encapsulated gel breaker for fracturing” amendment No.01 and Amendment No. 02 stipulate that the viscosity retention rate of encapsulated gel breaker for fracturing (70℃, 1h, the dosage of encapsulated gel breaker is 0.01%) is not less than 70%.
Since the viscosity retention rate and release rate of the encapsulated gel breaker are a pair of contradictory technical indexes, that is, after the encapsulated gel breaker is added in the fracturing process, it is necessary to maintain the high viscosity of the fracturing fluid without affecting the rheological properties and sand carrying performance of the fracturing fluid, and it is necessary to completely break the gel of the fracturing fluid after the fracturing construction, and it is easy to flowback, so as to reduce the damage to the formation. Therefore, the tradeoff between the release rate and the viscosity retention rate of the encapsulated gel breaker for fracturing is particularly important, which needs to be determined by a large number of tests.
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Post time: Sep-05-2023