Novel gemini surfactant as a clay stabilizing additive in fracturing fluids for unconventional tight sandstones: Mechanism and performance

Abstract

The effect of clay particles on reservoir performance and nearby formations depends on its swelling properties, cation exchange capacity, and morphology. In this study, a novel synthesized gemini surfactant is used as an additive in fracturing fluid to stabilize the clays in an unconventional tight sandstone rock fracturing. The effect of clay swelling on the tensile strength of the tight sandstone rock is quantified using breakdown pressure experiments. Petrophysical alterations are evaluated using coreflooding experiments. Micro computerized tomography, scanning electron microscope, and nuclear magnetic resonance tests were done before and after each coreflooding experiment to evaluate the formation damage. Similar experiments were carried out without any clay stabilizer (deionized water) and with different commercial clay stabilizers used in fracturing fluids (3 wt % NaCl, and 3 wt % KCl), to compare and evaluate their clay swelling capacities with gemini surfactant. Scioto sandstone samples with average liquid permeability around 0.3 mD and average porosity around 14–16% were used. The X-ray diffraction analysis showed the presence of illite, chlorite, and kaolinite clays in the studied Scioto sandstone samples. Breakdown pressure measurement test results showed that the use of novel gemini surfactant solution as clay stabilizing additive resulted in a significantly lower fracture pressure compared to the deionized water, 3 wt % NaCl, and 3 wt % KCl solutions. Breakdown pressure with gemini surfactant was 746 psia, with 3 wt% KCl was 797 psia, with 3 wt% NaCl was 845 psia, and deionized water showed very higher breakdown pressure of 905.9 psia. The reduction in breakdown pressure is attributed to the clay stabilization capacity of the novel gemini surfactant. Permeability measurements from the coreflooding experiments also confirmed the clay stabilization capacity of the gemini surfactant. Micro computerized tomography and nuclear magnetic resonance showed that the rock samples saturated with deionized water, 3 wt % NaCl, and 3 wt % KCl resulted in the reduced porosity due to the swelling of illite, while the gemini surfactant maintained the porosity due to clay stabilization.