Analyzing the impact of the interaction between hydraulic fracturing fluid and Kerogen on its wettability alteration

Abstract

The increasing demand for exploring and developing unconventional reservoirs has sparked active research into hydraulic fracturing. However, the effect of hydraulic fracturing fluid on kerogen wettability alteration resulting from their interaction remains inadequately understood. This study aims to experimentally quantify the impact of hydraulic fracturing fluid on kerogen wettability alterations as a function of thermal maturity level. To achieve this objective, kerogens isolated from various organic-rich shale rocks of different types and maturities were mixed with synthetic hydraulic fracturing fluid at a temperature of 80 °C for 14 days. The resulting kerogen wettability was analyzed with the sessile drop method, Ion Chromatography (IC), and Attenuated Total Reflectance Fourier-Transform Infrared spectroscopy (ATR-FTIR), while Rock-Eval pyrolysis experiments were conducted as well to determine the kerogen geochemistry changes. After experiments, ANSYS-CFD was utilized to conduct numerical simulations of two-phase fluid flow to identify the impact of wettability on gas-water relative permeability.This study experimentally demonstrated that hydraulic fracturing fluid interacting with kerogen results in significant wettability alterations, which depend on the type and maturity of the kerogen. The Drop Shape Analyzer (DSA) results revealed that the air/water-contact angle decreased after the reaction for every type and maturity of kerogen, although the wettability alteration was greater with higher kerogen maturity. The ATR-FTIR findings revealed that mature kerogen isolates experienced a reduction in their hydrophobic functional groups, whereas kerogen isolates with relatively lower maturity demonstrated a potential loss of such groups, possibly resulting from oxidation. This trend toward hydrophilicity is consistent with the DSA results. The numerical modeling results indicated that the relative permeability was strongly influenced by the wettability of the formation. A water-wet formation led to a higher water relative permeability compared to the relative permeability of gas, and vice versa. These results represent a significant step forward in assessing multiphase fluid transport in organic-rich shales and hydrocarbon production.