Lightweight cements are utilized in oil well applications, mostly where the rock formation is weak or fractured and requires a lower density and more stable cementitious material, which applies lower pressure. This is required very often in shale fields where long horizontal wells are drilled and cemented. In US this type of cement has been mostly utilized in the Permian oil basin, in West Texas and Southeast New Mexico.  

FlexCem®

In 2017 Buzzi Unicem USA partnered with Trabits Group to exclusively produce FlexCem®, a new patented lightweight variable-density well cement developed by the Trabits Group. It is manufactured using patented technology in which clinker and a proprietary zeolite are interground in specific ratios to improve setting and strength cement properties in oil wells. FlexCem® key characteristics is the utilization of ferrierite, a particular type of zeolite. Zeolites are aluminosilicates, pozzolanic in nature, having a unique cage structure and are normally utilized in ion exchange, desiccants and catalyst applications. About 40 types of zeolites are currently known. Decades-long research and testing by Halliburton and Trabits Group discovered that ferrierite could be used in manufacturing of lightweight cement giving superior cementitious properties in comparison with traditional lightweight cement. The key characteristics of FlexCem® are:

•  Allows for density adjustments within a single blend without adversely affecting well slurry properties
•  Maintains accurate consistent densities throughout the job without significant changes in viscosity
•  Provides thermal stability with little or no strength retrogression
•  It is saltwater resistant, very important for offshore utilization
•  It has high compressive strength

Trabits Group owns the only large mineable deposit of ferrierite known in the world, located in the remote town of Lovelock, Nevada.

FlexCem® is produced intergrinding normal clinker with ferrierite and gypsum at about 7,000-7,500 Blaine. Ferrierite being softer than clinker preferentially grinds to a smaller particle size resulting in a bimodal particle size distribution.  The specific gravity of the cement, a key parameter in the production process, is maintained in the 2.75-2.85 range. The resulting density of the slurry can be as low as 10.5 ppg (pound per gallon).

With a clinker to cement ratio lower than 65%, FlexCem® is also a green cement, with low carbon emissions in the production process. Buzzi Unicem USA started to test FlexCem® production in the Pryor, OK plant first and after that in the Maryneal, TX plant. Results were positive and in 2019 three separate campaigns were completed. The product was sold first in August 2019 from the Maryneal plant.

The market of lightweight cement is forecasted to expand significantly in the next years and, with FlexCem®, Buzzi Unicem USA will be able to compete in this growing market.  There are also other potential applications of FlexCem®, for example in geothermal applications and in oil well drilling fluids, which are currently being researched and tested.