Thomas Welton - Maintaining Well Productivity Through Inhibiting Scale Formation and Controlling Fines Migration

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      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.

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