Abstract
Resin consolidation of the near-wellbore (NWB) region is often performed to control sand production. However, when the formation is composed of a higher content of clays and fines, particularly when the swellable clay content is higher than 4%, it can be challenging to treat the formation and obtain good consolidation with acceptable retained permeability. Possible reasons for this include: 1) smaller grain size and smaller pore throats can hinder any resin coating, affecting the retained permeability and 2) the resin can enter into the interlayer and swell the clays infinitely, eventually blocking the pore throats.
Improved methods to provide consolidation to clay-laden formations are described based on laboratory testing and analysis. The effects of various treatment methods, such as using clay-control agents during the preflush stage of the resin treatment and reducing the viscosity of the resin treatment fluid to obtain optimum consolidation and retained permeability, are discussed.
The present method uses cationic organic polymers (COPs) in the preflush that can control swelling clays followed by less-viscous resin treatment fluid, which can form a thinner coating around grains and provide acceptable strength without significantly compromising regain permeability.
Laboratory testing was performed on various formation sands having higher clay content, 5 to 10%, combined with fines ranging from 5 to 15%. The results showed that traditional resin consolidation treatments do not provide acceptable retained permeability and consolidation strength. Using COPs in the preflush provided improved retained permeability. Using a combination of COPs in the preflush and a diluted resin treatment provided significantly improved results. This shows that COPs help prevent clays from swelling. The resin cannot enter the interlayer and swell clays any further, thus improving retained permeability. Additionally, when the treatment fluid is diluted, it can penetrate uniformly throughout a sandpack, providing a thinner but sufficient coating of the resin to achieve good consolidation and also good retained permeability.
A novel method and composition for a resin consolidation service to obtain effective consolidation strength and acceptable retained permeability in clay-laden formations is demonstrated by means of laboratory testing of the actual formation sand.
Previously, it was impossible to consolidate a formation that possesses large amounts of fines and clays while maintaining retained permeability in an acceptable range. This new method is applicable in the field without requiring additional tools or more stages during the treatment procedure.
