The long-term integrity of rock-based geopolymers was studied in corrosive environments. The geopolymers were cured for 7 days at ambient conditions. Afterwards, the geopolymers were exposed to crude oil, brine and H₂S in brine at 100 °C and elevated pressures. The compressive strength, tensile strength, weight and volume changes were measured prior and after 3, 6 and 12 months of exposure. The measurements showed a turning point after 6 months of ageing. Whereas the compressive strength and tensile strength started to increase when the specimens were exposed to crude oil and brine, the specimens that were exposed to H₂S experienced some degradation. Permeability of geopolymers before exposure and after 12 months of exposure to the crude oil and brine was very low. The permeability of the specimens which were exposed to H₂S was not measureable. Substantial volume changes were observed for the geopolymers which were exposed to H₂S and brine.

In this experimental study, two different cementitious materials, including (i) a class of expansive cement currently used for plug and abandonment (P&A) operations and (ii) a non-cement-based naturally occurring rock, known as geopolymer, are selected to examine the hydraulic bond strength and shear bond strength. Clean machined steel and rusty corroded steel were selected to represent the casing. The test samples were cured at 90 °C considered as bottom-hole static temperature (BHST) and under elevated pressure of 17.2 MPa for 1 week. The hydraulic sealability of the barrier materials tested up to 3.4 MPa of differential pressure. The results indicated that additives used in slurry preparation impact the hydraulic sealability of the material. Additionally, the rusty corroded steel provided a better hydraulic sealability comparing to the clean machined steel for the same cementitious material. The shear bond strength test was performed by running the push-out test. According to the present test observations, no correlation was found between the shear bond and hydraulic bond strength of different barrier materials. The geopolymer showed the lowest shear bond strength, while it provided the highest hydraulic sealability.

Summary: Our objective is to present selected rheological and mechanical properties of rock-based geopolymers contaminated with different concentrations of drilling fluids. The possible flash setting and the maximum intake of drilling fluids before seeing a dramatic deterioration of the geopolymers are presented. Rock-based geopolymers designed for cementing conductor and surface casing were prepared and cured for up to 28 days at 22°C and atmospheric pressure. Water-based drilling fluids (WBDFs) and oil-based drilling fluids (OBDFs) were designed in accordance with the recommendations from the petroleum industry. The fluid samples were prepared, and their viscous behavior was characterized before and after hot-rolling. The geopolymeric slurries were mixed and then blended with the prepared drilling fluid volumes. The contaminated geopolymeric slurries were cured and tested at different time intervals. American Petroleum Institute (API) Class G neat cement was used as a reference. These samples were cured and contaminated with the same drilling fluids. The properties of contaminated geopolymer slurries were benchmarked with those of the contaminated Class G cement. The obtained mechanical properties showed that the rock-based geopolymers are more sensitive to WBDFs than to OBDFs. However, for contaminated Portland cement samples, the obtained results were opposite, and the contamination effect of OBDF on cement was more noticeable than WBDF. The impact of geopolymer contamination is a function of curing time. Although geopolymeric samples showed dramatic strength retrogression at the early time, strength buildup of the samples compensated for the impact of contamination.