2,803
edits
Changes
Jump to navigation
Jump to search
Line 105:
Line 105: − +
Rock-water reaction: formation damage (view source)
Revision as of 22:36, 12 March 2014
, 22:36, 12 March 2014→Clay type
===Clay type===
===Clay type===
Clay type influences the brine salinity at which clays start to deflocculate. Higher cation exchange capacity clays require higher salinity to prevent clay deflocculation. Smectite, illite, and kaolinite have cation exchange capacity (CEC) values of approximately 100, 20, and 5, respectively, Thus, total brine cation concentration must be higher to prevent smectite dispersion, followed by lesser concentrations for smectite-illite mixed layer clay, illite, and kaolinite clays, respectively.<ref name=pt05r139>Scheuerman, R. F., Bergersen, B. M., 1990, Injection-water salinity, formation pretreatment, and well operations fluid-selection guidelines: Journal of Petroleum Technology, Sept., p. 836–845</ref>.
Clay type influences the brine salinity at which clays start to deflocculate. Higher cation exchange capacity clays require higher salinity to prevent clay deflocculation. Smectite, illite, and kaolinite have cation exchange capacity (CEC) values of approximately 100, 20, and 5, respectively, Thus, total brine cation concentration must be higher to prevent smectite dispersion, followed by lesser concentrations for smectite-illite mixed layer clay, illite, and kaolinite clays, respectively.<ref name=pt05r139>Scheuerman, R. F., Bergersen, B. M., 1990, Injection-water salinity, formation pretreatment, and well operations fluid-selection guidelines: Journal of Petroleum Technology, Sept., p. 836–845</ref>
Chlorite exhibits essentially no water sensitivity. It contains iron and it can react with spent HCl acid if the pH rises above 1.0. A pore-plugging ferric hydroxide precipitate with a hydrated gel-like structure can form unless an oxygen scavenger and iron-chelating or iron-sequestering agents are used.
Chlorite exhibits essentially no water sensitivity. It contains iron and it can react with spent HCl acid if the pH rises above 1.0. A pore-plugging ferric hydroxide precipitate with a hydrated gel-like structure can form unless an oxygen scavenger and iron-chelating or iron-sequestering agents are used.