Efficiency of magnesium hydroxide as engineering seal in the geological sequestration of CO 2

Abstract

Injection of CO 2 at depth will cause the acidification of groundwater. As a preliminary study for the potential use of MgO as an alternative to Portland cement in injection wells, MgO carbonation has been studied by means of stirred batch experiments under subcritic (pCO 2 of 10 and 50 bar and T of 25, 70 and 90 °C) and supercritic (pCO 2 of 74 bar and T of 70 and 90 °C) CO 2 conditions. Magnesium oxide reacts with CO 2-containing and Ca-rich water nearly equilibrated with respect to calcite. MgO quickly hydrates to brucite (Mg(OH) 2) which dissolves causing the precipitation of magnesium carbonate phases. Precipitation of these secondary phases (magnesite and/or metastable phases such as nesquehonite (MgCO 3 •3H 2 O) or hydromagnesite (Mg 5 (CO 3) 4 (OH) 2 •4(H 2 O)) depends on pCO 2 , temperature and solid/water content. In a constant solid/water ratio, the precipitation of the non-hydrated Mg carbonate is favored by increasing temperature and pCO 2. MgO efficiency; Dávila et al. (2016) 2 The experimental variation of Mg and Ca concentrations and pH over time at the different temperatures and pCO 2 has been simulated using the CrunchFlow reactive transport code. Simulations reproduce the experimental evolution of the aqueous concentrations and indicate a decrease in porosity when increasing temperature and pCO 2. This decrease in porosity would be beneficial for the sealing properties of the cement. These results have been used in the simulation of an application case with a deep borehole surrounded by MgO cement at 90 °C.

Evaluation of Effectiveness of CO2 Sequestration Using Portland Cement in Geological Reservoir Based on Unified Pipe-network Method

“…The atmospheric pressure on the top boundary is 10 bar. CO 2 leakage at a constant flow velocity (1.25 −5 m/s) and concentration (316 mol/m 3 ) at the bottom boundary [2]. The concentration of CO 2 (g) is redefined as the concentration of CO 2 (aq) in groundwater.…”

“…Hence, some measures should be implemented due to the the existence of discrete fracture networks. As one of the most effective methods, using CO 2 -reactive or CO 2 -consuming solution to form precipitation clogging the voids of the formation to reduce the porosity and hydraulic conductivity of the rock and minimize CO 2 emission have been developed [1][2][3][4][5]. Thus, it's very important to evaluate the effectiveness of CO 2 sequestration using portland cement in geological reservoir.…”

Evaluation of effectiveness of CO₂ sequestration in geological reservoir based on Unified Pipe-network Method

“…The atmospheric pressure on the top boundary is 10bar. CO 2 leakage at a constant flow velocity (1.25 −5 m/s) and concentration (316 mol/m 3 ) at the bottom boundary [2]. The concentration of CO 2 (g) is redefined as the concentration of CO 2 (aq) in groundwater.…”

“…Hence, some measures should be implemented due to the the existence of discrete fracture networks. As one of the most effective methods, using CO 2 -reactive or CO 2 -consuming solution to form precipitation clogging the voids of the formation to reduce the porosity and hydraulic conductivity of the rock and minimize CO 2 emission have been developed [1][2][3][4][5]. Thus, it's very important to evaluate the effectiveness of CO 2 sequestration using portland cement in geological reservoir.…”

The Role of the Solvent in Determining the Surface Texture of Magnesium Hydroxide

“…Solid magnesium oxide and hydroxide is used in various processes and finds many applications in a variety of fields such as water treatment [1][2][3], heat storage [4,5] CO 2 storage [6,7] and sound absorption [8] among many others. As a result its surface chemical and textural properties have been extensively studied by several authors.…”