Results from Response Surface Methodology in the Study of Novel Temporary and Permanent Clay Stabilizers

The performance results from a systematic study of novel and contemporary clay stabilizers are provided. These interactions range from synergistic to antagonistic and are presented on a response surface with good correlation. Both organic and inorganic permanent and temporary clay stabilizers were studied. Some of these novel effective inhibitors have HIMS ratings lower than choline chloride.

Various clay stabilizers are employed when stimulation techniques requiring aqueous based fluids are necessary in water sensitive formations. Typically, if swelling or migrating clays are present, temporary or permanent stabilizers are utilized. Low molecular weight temporary stabilizers, as a rule, perform only above a critical level concentration, but as the stabilizer's concentration diminishes in the fracturing fluid due to flowback, formation fluid displacement, or other mechanisms, the clay can swell, reducing porosity and permeability. Permanent stabilizers are generally higher molecular weight and can adhere to single or multiple clay platelets, thus dissolution of the stabilizer into the fluid is not favored, and the beneficial anti-swelling effect is of higher duration.

This study was set up using Central Composite Design of Experiments. Performance testing was conducted using a low pressure Bariod fluid loss cell. A set concentration of unbenefited sodium bentonite was blended into water at a specific RPM and duration in the presence of the particular stabilizers, then placed in the cell, sealed, and pressure was applied. Finally leak off rates were measured. The slope of the leak off curve was calculated and plotted versus dosage. The slopes and response surfaces observed had excellent correlation. Additive effects and synergies were noted.

The design of efficient temporary clay stabilizers can be directly linked to performance. Novel temporary clay stabilizers competitive with choline chloride in both performance and environmental profile should be welcomed in stimulation. The duration of the stabilization could also be studied using this test method since porous media experimentation is difficult to perform.