A Novel Chemical System for Sand Consolidation in Clay-Rich Reservoirs

Summary Excessive sand production presents a significant challenge in oil and gas wells, leading to wellbore instability, equipment damage, and reduced productivity. Chemical sand consolidation using epoxy resin–based systems is a promising solution for mitigating sand migration while maintaining reservoir permeability. In this study, we introduce an optimized integrated chemical formulation, combining epoxy resin with a clay inhibitor to enhance sand consolidation in clay-rich formations. The research was structured into three phases: (1) formulation optimization using response surface methodology with a Box-Behnken design to achieve the optimal balance between gelation time, clay swelling inhibition, and compressive strength; (2) rheological characterization of the integrated chemical to evaluate viscosity behavior at elevated temperature; and (3) sandpack experiments to assess consolidation efficiency and permeability retention. The optimized formulation consisted of an epoxy-to-hardener ratio of 2.5:1, 10 wt% loading of a 1 wt% aqueous poly(diallyldimethylammonium chloride) (PDADMAC) solution as the clay inhibitor, and 29.55 wt% xylene, resulting in a gelation time of 461 minutes, a 90% reduction in clay swelling, and a compressive strength of 523 psi. Experimental validation confirmed that the predicted and actual results were within a 10% margin of error. Post-optimization evaluation revealed that increasing the PDADMAC concentration in the solution from 1 wt% to 3 wt%, while maintaining the same 10 wt% loading, resulted in nearly 0% clay expansion, highlighting its effectiveness in stabilizing bentonite. The sandpack experiment demonstrated that the optimized formulation maintained more than 90% permeability retention in low-clay formations but decreased significantly at higher clay concentrations. The compressive strength was the highest (674 psi) in clay-free sandpack, while increasing clay content beyond 10 wt% reduced strength to 400 psi at 40 wt% bentonite, indicating a trade-off between permeability and mechanical integrity. Overall, this study establishes an optimized epoxy-based chemical system that effectively consolidates sand while mitigating clay swelling and preserving permeability, making it a viable solution for oil and gas well applications in unconsolidated and clay-bearing formations.