Frictional behavior of dolomite-rich fault gouges: Effects of mineralogical heterogeneity and implications for induced seismic risk in carbonate reservoirs

This study investigates the frictional behavior of dolomite fault gouges and related minerals (MgO, magnesite) to elucidate mechanisms underlying induced seismicity in carbonate reservoirs. We conducted controlled shear experiments under varying stress conditions and mineral compositions, including pure dolomite, MgO, magnesite, and homogenized/layered gouges. These experiments enabled analysis of friction coefficients and rate-state parameters ( a–b ). Results show that MgO and dolomite gouges exhibit velocity-weakening behavior at low effective stresses (0.5 MPa), transitioning to velocity-neutral or velocity-strengthening behaviors with increasing stress. Uniform mixtures of dolomite and MgO display an unexpected friction coefficient increase ( μ = 0.68−0.95), attributed to MgO particle bearing force chains. In contrast, stratified configurations exhibit friction stability similar to pure dolomite. Dolomite fragmentation under shear stress promotes interparticle locking and stress homogenization, whereas MgO resists fracturing, amplifying shear resistance. Cryptocrystalline magnesite demonstrates higher friction coefficients ( μ ≈0.83) compared to phanerocrystalline magnesite ( μ ≈0.65), underscoring grain-size effects. Importantly, historical coseismic slip and MgO accumulation in fault zones reduce stability thresholds, increasing susceptibility to transient stress perturbations (e.g., fluid injection). These findings highlight the dual control of mineralogical heterogeneity and stress conditions in modulating fault stability, providing insights for mitigating induced seismicity in dolomite-rich reservoirs. • Dolomite and MgO gouge transfer to velocity weakening under low effective stress. • Mixed gouge friction coefficient is greater than that of single component sample. • The heterogeneity of geometric distribution will affect the velocity dependence. • The mineralogical transformation of dolomite can promote seismicity nucleation.