Boron based crosslinkers are commonly used to increase viscosity, and improve fluid loss control and proppant transportability of guar and its derivative fluids. Boron crosslinkers are usually preferred because of their ability to reheal after shearing and their favorable environmental properties. More efficient crosslinkers capable of cross-linking fluids with reduced polymer loading have always been of great interest to reduce formation and proppant pack damage from polymer residues, and to reduce overall fluid cost, especially with reduced availability and higher cost of guar.
We recently reported in SPE 140817 the synthesis of poly-aminoboronates, bulky compounds containing multiple boron sites and capable of interacting with multiple polysaccharide strands to form more complex crosslinking networks at lower polymer loadings than conventional guar fluids. However, to improve the marketability and acceptance of the product, a lower-cost combination of raw materials is sought. In addition, a delaying mechanism to improve the control of the fluid viscosity buildup can make the product fit into broader applications.
A readily available polyamine was used as the base scaffold, and boron incorporated via intermediate borate formed in the condensation reaction between boric acid and ethylene glycol to replace volatile and highly flammable trimethylborate. New chemistry was developed to produce more controlled crosslinking. The resulting compound exhibited desired adjustable delay characteristics.
This paper will show effect of a series of new crosslinkers in terms of delay properties. Testing results of fluids with 20% lower polymer loading, crosslinked with the new crosslinker will be reported and compared to conventional fluids. Analysis and discussion of the chemistry, crosslinker performance, and economics will be presented.