What is the phenomenon that occurs from a sudden decrease in salinity of a brine flowing through a sandstone that will cause formation damage by dispersing clay particles?

What is the phenomenon that occurs from a sudden decrease in salinity of a brine flowing through a sandstone that will cause formation damage by dispersing clay particles?

• A. Water Sensitivity
• B. Osmotic Swelling
• C. Salinity Shock
• D. Clay Flocculation

Answer: (A)

Water sensitivity shows up when clay-bearing rock reacts to contact with relatively fresh water. In sandstone with clay minerals, high-salinity brine keeps the clay particles in a flocculated, stable arrangement. A sudden drop in salinity lowers the ionic strength around the clays, the diffuse double layer surrounding each particle expands, the clays hydrate more, and the particles disperse rather than stay clumped. Those dispersed fines can migrate and clog pore throats, reducing permeability and causing formation damage. That dispersion of clay particles due to a rapid salinity decrease is exactly what is described, making water sensitivity the best fit.

Water sensitivity shows up when clay-bearing rock reacts to contact with relatively fresh water. In sandstone with clay minerals, high-salinity brine keeps the clay particles in a flocculated, stable arrangement. A sudden drop in salinity lowers the ionic strength around the clays, the diffuse double layer surrounding each particle expands, the clays hydrate more, and the particles disperse rather than stay clumped. Those dispersed fines can migrate and clog pore throats, reducing permeability and causing formation damage. That dispersion of clay particles due to a rapid salinity decrease is exactly what is described, making water sensitivity the best fit.