Enhanced Sulfate Resistance of Oil Well Cement Using a Polyacrylate-Dimethylaminoethyl Methacrylate Hydrogel

The purpose of the present study is to verify the effect of hydrogel on the corrosion resistance of oil well cement in a sulfate-rich environment. A poly-(acrylic acid-<i>co</i>-dimethylaminoethyl methacrylate) (PDA) hydrogel was then synthesized using free radical aqueous polymerization with acrylic acid (AA) and dimethylamethyl methacrylate (DMAEMA) as the monomers. The effect of the hydrogel on the mechanical properties and sulfate resistance of cement, in addition to the corresponding mechanism, was studied. The results showed that the PDA hydrogel was successfully synthesized. It could reach the low critical solution temperature (LCST) of 50 °C. Sulfate attack tests demonstrated that the C3 cement (with 0.3% PDA) exhibited the smallest loss in mass and strength. Furthermore, the Ca-(OH)₂ mass loss rate of C3 cement was 50.06% (Na₂SO₄) and 69.37% (MgSO₄) of C0 cement (with 0% PDA). The sulfate-induced erosion depths on the C3 cement were 26.72% (Na₂SO₄) and 64.62% (MgSO₄) of C0 cement. PDA hydrogel played the role of internal curing in cement, increased the densification of cement around hydrogel, hindered the sulfate attack, and improved the sulfate resistance of cement.