Details

Autor(en) / Beteiligte

• Choens, R. C.
• Wilson, J.
• Ilgen, A. G.

Titel

Strengthening of Calcite Assemblages Through Chemical Complexation Reactions

Ist Teil von

• Geophysical research letters, 2021-11, Vol.48 (22), p.n/a

Ort / Verlag

Washington: John Wiley & Sons, Inc

Erscheinungsjahr

2021

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Utilization of subsurface reservoirs, including fluid extraction/injection, can induce stress changes and modify in‐situ chemical equilibrium causing subcritical fracturing and deformation. Here, we show that chemical complexation reactions at the newly created fracture surfaces within the crack tip limit fracturing during consolidation of granular calcite assemblages. Previously, we showed that analogous chemical complexation reactions can increase in‐situ fracture toughness in pre‐fractured single crystal calcite. To test the chemical complexation effect under subsurface conditions, we consolidated samples under increasing hydrostatic pressure to induce widespread intergranular fracturing in the presence of fluid containing common anions. Measured consolidation, acoustic emissions, and microfracturing demonstrate that deformation correlates with complexation affinity for calcium in calcite and aqueous anions. We observed that deformation is lowest in the presence of strongly complexing anions (e.g., sulphate), provided sufficient anion diffusion rates. This understanding is important for predicting reservoir effective strength in the presence of complex aqueous fluids. Plain Language Summary The current study identifies chemical reactions at the crack tip of calcite that control the extent of fracturing during consolidation. Calcite is one of the most abundant minerals in the Earth's crust; however, the chemical mechanisms that could promote or arrest crack growth in calcite are poorly understood. Microscopic cracks in individual calcite grains could affect reservoir‐scale processes such as deformation and subsidence. Here, we show that chemical reactions at the crack tips of calcite define fracturing behavior and, therefore, consolidation at pressures typical for geologic formations. Key Points We examined how the formation of surface complexes affects fracture‐driven consolidation in granular assemblages of calcite More fracturing and faster consolidation of calcite grain packs are observed in fluids containing anions with weak affinity for calcium Strongly complexing anions can effectively shield crack tips from hydrolysis reaction and modify deformation rates and total strains