Chemical–mechanical coupling observed for depleted oil reservoirs subjected to long-term CO2-exposure – A case study of the Werkendam natural CO2 analogue field

Chemo‐mechanical behavior of clay‐rich fault gouges affected by CO2‐brine‐rock interactions

“…Similar chemo‐mechanical behavior has been seen in gouges derived from reservoir rock taken from natural CO 2 fields (unexposed and CO 2 ‐exposed Entrada Sandstone, Green River, UT, USA and Röt Fringe sandstone, Werkendam, Netherlands. ) These observations suggest that the initial mineralogy of the fault gouge (and local variations therein) imposes a stronger control on fault behavior than the extent of CO 2 ‐brine‐rock interactions, even after multiple pore volume flushes.…”

“…post abandonment of the field). 12,13,[35][36][37] One of the challenges encountered in laboratory studies investigating the long-term effects of CO 2 exposure is the slow reaction of aluminosilicates and the storage integrity timescales required by many regulators (>10 000 years), which are typically much longer than available laboratory timescales (weeks, months or occasionally a few years; see Rochelle et al 38 and references therein).…”

CO2‐induced chemo‐mechanical alteration in reservoir rocks assessed via batch reaction experiments and scratch testing

“…19,44,45 Small amounts of mineral dissolution can produce large effects on mechanical properties if the dissolved minerals are load-bearing (normal and shear stresses) and locate at specific places in the rock skeleton. 8,46 Dissolution of hematite coating cements in Entrada Sandstone is one example.…”

“…Long‐term exposure to CO 2 ‐brine mixtures at natural CO 2 accumulations has resulted in alteration of mechanical properties including: strengthening in Navajo Sandstone, sandstones of the Salt Wash Member of the Morrison Formation and Mancos Shale, and weakening in Entrada Sandstone, Summerville Siltstone, and portions of the Röt Fringe Sandstone . Despite bulk mechanical alterations triggered by naturally occurring CO 2 , the sliding friction coefficient of some sandstones exhibit negligible changes upon mineral dissolution and precipitation …”

“…[4][5][6] Long-term exposure to CO 2 -brine mixtures at natural CO 2 accumulations has resulted in alteration of mechanical properties including: strengthening in Navajo Sandstone, sandstones of the Salt Wash Member of the Morrison Formation and Mancos Shale, and weakening in Entrada Sandstone, Summerville Siltstone, and portions of the Röt Fringe Sandstone. [7][8][9] Despite bulk mechanical alterations triggered by naturally occurring CO 2 , the sliding friction coefficient of some sandstones exhibit negligible changes upon mineral dissolution and precipitation. 9,10 Alteration of rocks with CO 2 -brine in the laboratory also results in measurable changes in geomechanical and transport properties, such as increased permeability and porosity, 11 dissolution of siliceous and carbonate minerals, 12 reduction of indentation stiffness, 13,14 reduction of fracture toughness, 7 and decrease of the size of yield stress locus.…”