Stabilizing Wellbores in Unconsolidated, Clay-Laden Formations

Abstract

Summary This article presents results of laboratory and field testing regarding the effectiveness of an improved, one-component, low-viscosity resin-consolidation system. The system is designed to stabilize or strengthen the unconsolidated formation sand surrounding a wellbore and to overcome the effects of cyclic loading, while minimizing reduction of original permeability. Treatment-fluid volumes, overflush fluid, and the chemical composition of the consolidation material were found to directly impact the consolidation performance and the retained permeability of the treated formation sand. The treatment renders formation fines immobile so that migration and plugging do not occur. This study determined that application of a consolidation material containing a specific solvent chemistry for clay-laden sands resulted in excellent strengths, even at high clay contents. This finding indicates that the consolidation material was drawn onto the mineral surfaces, resulting in minimal loss in effective porosity. Scanning electron micrographs of the consolidated-core material clearly revealed the entrapment of fines as the consolidation material formed a thin film on the mineral surfaces, causing little damage to the porosity and permeability of the formation. Results of field testing indicate that the consolidation treatment effectively stopped the production of formation sand and fines while maintaining the production of the wells at desirable flow rates. The technique provides a very attractive alternative to conventional sand-control completions in lower quality reservoirs, as well as an effective through-tubing completion alternative.