Crystallisation temperature is an important property of well construction and intervention fluids that are used in cold weather conditions and / or under high pressure. True crystallisation temperature (TCT) has historically been used to define the performance ceiling of oilfield brines and fluids. In traditional oilfield brines and fluids there is typically only a small difference (safety margin) between the TCT as measured by standard laboratory procedures and the fluids’ performance ceiling in the field. Formate brines behave very differently from other oilfield brines as they exhibit an enormous supercooling effect and metastable crystals can form in potassium formate brines. This makes it very difficult to measure formate brines’ TCTs using standard laboratory methods. It also makes it difficult to use the measured TCT data to determine the performance ceiling of the brines in the field.

 

This section of the manual presents measured TCT data for sodium, potassium and cesium formate single-salt brines and cesium / potassium formate brine blends. A special seeding method that is used and recommended by Cabot Specialty Fluids is described, along with guidelines for how to apply measured TCT data in the field, and how to lower TCTs of formate brines. Pressurized TCT data (PCT data) from formate brines are also presented.

 

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