A Geopolymer Based Oil and Gas Well Cementing Material

Geopolymer is a kind of inorganic polymer made from alkali activator and gel material. It has a 3D network structure formed by SiO₄ and AlO₄ tetrahedra. Geopolymer has excellent mechanical performance, high bonding strength with inorganic substrate and good mobility. In oil and gas well cementing, the mud cakes remained on the borehole wall cause poor cementation of the cement sheath with the borehole wall. To solve this problem, metakaolin (MK) was added to form a geopolymer with the clays in the drilling fluid to improve the quality of well cementing operation. Using water glass and MK (at a concentration of 2.5%), a geopolymer based well cementing material with low viscosity and high porosity was developed. The glass modulus (M) of the geopolymer was 1.5, and it can effectively penetrate mud cakes at both normal and high pressures. After being solidified at 90 ℃ for 10 hours, the compressive strengths of the mud cake were 3.0 MPa and 1.0 MPa, respectively. Meanwhile, the solidified mud cakes can enhance the bonding strength of the cement sheath with the borehole wall, the bonding strengths of the “borehole wall – cement sheath” interface and the “casing – cement sheath” interface were 0.6 MPa and 1.0 MPa, respectively. XRD analysis revealed that although the addition of MK cannot change the crystallization property of the mud cakes after final solidification, it to some extent increases the concentrations of the gel materials in the mud cakes, which further increases the compressive strength and bonding strength of the solidified mud cakes.