Aqueous based zirconium crosslinked fracturing fluids have seen widespread service since the early 1980's. Today, zirconium crosslinkers are used with many types of polymer solutions, across a pH range of from less than 1 to greater than 12. at bottom-hole temperatures of from less than 100F to greater than 400F. There is no doubt among workers in the field that the same zirconium crosslinked fracturing fluid is not suitable for such a wide range of applications, and, yet, there has yet to be published a systematic evaluation of the impact first order changes in the composition of zirconium crosslinkers have on rheological performance. This study endeavors to provide such a systematic evaluation.
Aqueous-based zirconium crosslinked systems can be made with a wide range of functionality to meet specific performance needs. In hydraulic fracturing fluid systems utilizing zirconium crosslinked guar or guar derivatives, changes in the crosslinker due to differences in the zirconium raw material source, the ligand to metal ratio, cation type, and pH of the system cause significant differences in rheological performance. In particular, crosslink time, temperature and stability at temperature (for a given shear regime) can be controlled by manipulation of the aforementioned factors. This study presents a systematic evaluation of these factors and discusses how an understanding of their interrelationships is essential in predicting performance of a crosslinker or designing a new fluid system.