Publication Details (including relevant citation information):
Nguyen, Philip Duke, Vasquez, Julio Estuardo, Weaver, Jim D., Welton, Thomas Donovan -
Abstract: Abstract Migration of fine particulates and/or scale formation is known to plug up etched channels or pore spaces in proppant packs, causing production decline in wells that have been acidized or completed with high-rate water packs or frac-packs. The removal of such damage caused by plugging is only a temporary solution if the source of the plugging material is not mitigated. This paper presents the results of a series of laboratory tests aimed at demonstrating and quantifying the performance of a treatment fluid for stabilizing formation fines, inhibiting scale formation, and keeping flow channels open through damaged proppant packs after production has been restored. Packed beds of proppant and formation sands were used to simulate frac-pack conditions before and after remedial treatments. The treatment fluid was comprised of a salt-free, aqueous-based solution containing an environmental friendly clay-swelling inhibitor and a water-based agglomerating agent (WBAA). The results show that this WBAA system is applicable to most types of formations, including sandstones, carbonates, and coals. Once injected into the proppant pack and formation matrix, WBAA forms a thin film on the particulates, covering and anchoring them in place, without plugging pore throats. This thin coating does not harden, but remains flexible, allowing the treated formation to withstand high shear stress during high production flow rates. WBAA coating forms hydrophobic film-encapsulating particulate surfaces, inhibiting chemical reactions that lead to scale formation in the pack matrix. The experimental results show that WBAA treatments effectively mitigate the buildup of scale in various sand packs and successfully control the migration of formation fines into proppant packs to maintain well production. Introduction Wells completed with gravel packs, high-rate water packs, or frac-packs often respond with high productivity initially for some period of time. However, after this high initial production, the production flow rates begin to drop off, indicating the flow paths have been choked off. The well operators often perform acid treatments on proppant packs or frac-packs to help rejuvenate the well production after verification that the production decline was caused by fines plugging or scale deposit. The well production is often restored, but this is usually temporary. Formation fines continue to produce and invade the proppant pack because there is no cohesion between grains to anchor or cement the fine particulate in place. Similarly, scale precipitation reappears within the pore spaces of the formation matrix or proppant pack, or builds up in downhole tubing because the scaling conditions still exist. Scaling problems are often an issue in offshore fields that inject seawater for pressure maintenance. This study was performed to evaluate the mechanisms in which the coating of a water-based agglomeration agent on a formation particulate can significantly impact the migration behaviors of formation fines into the pore spaces of the formation or proppant pack and maintain their permeability. The effects of fines migration in unconsolidated and consolidated formations treated with WBAA solution are examined and compared to those of untreated materials. In addition to the aggregating property of WBAA solution, this study also examines its scale-forming mitigation in formation sand and proppant packs by changing particulate surfaces from hydrophilic to hydrophobic to minimize interaction between the scale-forming water and the solid substrate surface.