Abstract

The evaluation of clay control agents and fluoboric acid in sandstone matrix acidizing treatments was performed to determine their effectiveness to eliminate silt and clay (fines) migration in high rate wells. Field results indicate that fluoboric acid is effective in removing formation damage due to fines migration and prevents further migration in oil and gas wells. Conventional clay control agents used in an overflush to Mud Acid (hydrochloric - hydrofluoric acid) do not perform adequately. The study includes numerous wells with cased hole and inside casing gravel packed completions. All wells evaluated exhibited severe fines migration problems subsequent to conventional Mud Acid treatments attributed to exceeding the critical flow velocity for silt and clay. Once production had dramatically decreased, the wells were treated with fluoboric acid to compare their well performace with that following the Mud Acid treatments. Sustained production was observed following the fluoboric treatments indicative of fines stabilization. Detailed descriptions of the candidate selection and design procedures are given.