Clays are high surface area minerals that are usually deposited within the pore spaces of the reservoir rock. These clay minerals appear in may different forms and all can lead to varying types of formation damage. Kaolinite, illite, smectite and chlorite clays are the 4 primary clay types in sandstone formations. It is rare in Canada that carbonate formations contain clays in the porosity, but carbonates can have clays bound in the rock fabric that can be released when the carbonate is dissolved by acid.
Kaolinite clays form platelet type structures that when disturbed can migrate and plug pore throats near the wellbore where they can accumulate. Illite clays are very fine, hair like structures that also can be dislodged and flow towards the wellbore. Smectite, or montmorillonite, clay can absorb water molecules into their structure and cause swelling which will cause blockages in the pore throat. Chlorite is another migrating type clay with the main difference in that iron is a large part of its structure and it is partially soluble in HCl, therefore creating an opportunity for iron induced formation damage.
For many years, simple potassium chloride solutions were used to protect clays. As the potassium ion is positive, the potassium ion can enter into the structure of the negatively charged clay species and prevent water from affecting the clay.
To make logistics easier, potassium chloride substitutes were developed of which choline chloride is the most popular. Multiple varieties of polymers and chemicals have also been developed to offer long term stabilization of clays as well.
Kaliber Chemicals has the following product(s) available:
CC10-KS – Polymer based clay stabilizer