Fundamental Insights Into Recrosslinkable Granular Hydrogels for Fracture Remediation

Summary The concentration of prior recrosslinkable granular hydrogels was based on the assessments of their properties and petrophysical performance. However, there is no reported correlation of microstructural information of the hydrogels with their macroscopic bulk properties, hindering the deployments of such hydrogels to complex geological reservoirs. Herein, we report that the relationship of elastic modulus with angular frequency can assess the crosslinking nature of hydrogels from our reliable experiments. The covalently crosslinked hydrogels showed independence from angular frequency, whereas the ionically crosslinked sample had a strong dependence. We established a robust database of commonly used chemical crosslinkers for hydrogel synthesis with their thermal stabilities, where organic covalently crosslinked hydrogels showed much better thermal robustness than their physically bridged counterparts. Moreover, we found that oven aging is a more appropriate strategy to analyze structural integrity compared with thermal gravimetric analysis (TGA). Finally, we demonstrated structural differences between the heterogeneous interlinking approach and homogeneous void-free regenerative strategy and their influences on petrophysical properties of the in-situ reformed bulk materials. We give an in-depth analysis of fundamental insights into crosslinking assessments, thermal stabilities, and recrosslinking approaches for laboratory studies and field applications. The fundamentals illustrated herein offer a robust method to appraise granular hydrogels with crosslinkable function for fracture treatments in the petroleum industry.