Nanosized Magnesium Oxide With Engineered Expansive Property for Enhanced Cement-System Performance

Abstract

Summary The bulk shrinkage of cement sheaths in oil wells can result in loss of long-term zonal isolation. Expansive additives are used to mitigate bulk shrinkage. To compensate effectively for bulk shrinkage during the late plastic phase and the hardening phase of the cement system, the performance of the expansive additive needs to be regulated considering the actual cement system and placement conditions. This paper presents an introductory investigation on the potential engineering of nanosized magnesium oxide (MgO) (NM) through heat treatment for use as an expansive agent in oilwell-cement systems. In this study, the bulk shrinkage of a cement system was mitigated by introducing NM with designed reactivity to the fresh cement slurry. The reactivity of NM was controlled by heat treatment. A dilatometer with corrugated molds was used to measure the linear strain of samples cured at 40°C and atmospheric pressure. The effect of NMs differing in reactivity on tensile properties of cement systems cured for 3 days at 40°C was examined by use of the flattened Brazilian test. The reactivity of the NM played a key role in controlling the bulk shrinkage of the cement system. Addition of only 2% NM by weight of cement (BWOC) with appropriate reactivity was sufficient to maintain expansion of the cement system. Adding NM to the cement system also resulted in improved mechanical flexibility. The NM with highest reactivity caused the largest reduction in Young's modulus at 3 days and, in general, the ratio of tensile strength to Young's modulus improved through the addition of NM to the cement system. Our work demonstrates that controlling the reactivity of the additive is a promising method to mitigate bulk shrinkage of cement systems and thereby to sustain the mechanical properties of the cement sheath in the oil well at an acceptable level.

Recent Advances in Magnesia Blended Cement Studies for Geotechnical Well Construction—A Review

“…The measurement methods of particle size or particle size analysis have been also developed for over one century corresponding with the development of material science. For cement and cement-based material research, several methods can be used such as the sieve method (Aphane, 2007;Liska et al, 2008;Al-Tabbaa, 2009, 2012;Mo et al, 2010;Panesar and Mo, 2013;Dung and Unluer, 2016;Ruan and Unluer, 2017;Mo and Al-Tabbaa, 2020), dynamic light scattering (Jafariesfad et al, 2017b), laser scattering (Shand and Jin, 2020), SEM (Qafoku et al, 2015), Blaine specific surface area method (Al-Tabbaa, 2013).…”

“…The third way is to survey the linear autogenous strain (Sant et al, 2006;Lura and Jensen, 2007) under the assumption of isotropic deformation. Linear autogenous strain can be monitored with watertight corrugated molds equipped with a dilatometer (Jafariesfad et al, 2017b). This measurement method is only able to monitor the linear strain under low temperature (below water boiling temperature) and atmospheric pressure conditions.…”

“…And the magnesium oxide (calcined at 1,400 °C) is fit for the case of higher temperature up to 175 °C. In addition, the shear bond strength (at the cementing interfaces) was improved by the bulk expansion, and the permeability of the hardened cement sample was decreased on account of the in-situ expansion in the pore matrix of set cement. Jafariesfad et al (Jafariesfad et al, 2017b) investigated the impact of magnesia with different reactivity (70-260 nm in average particle size) on the expansion and tensile strength of some oil well cement slurry. They employed near ambient aging conditions (40 °C, atmospheric pressure) to cure their cement specimens.…”

Effect of micro-magnesium oxide admixture on rheological and compressive strength properties of class G well cement

“…After mixing, each cement slurry sample was immediately conditioned as per the atmospheric conditioning method (API, 2013). This conditioning could make the slurry more homogeneously dispersed and pre-hydrated (Jafariesfad et al, 2017). The atmospheric pressure consistometer used is Grace R M7210.…”

“…Using magnesium oxide is one of the promising ways to mitigate this problem (Suhascaryo et al, 2005;Rubiandini et al, 2005). In order to characterize the influence of magnesium oxide on the properties of OWC slurries, some studies have been carried out on the compressive strength (Buntoro, 2001), tensile strength (Jafariesfad et al, 2017), bulk volumetric variation (Mo et al, 2010;Jafariesfad et al, 2017), micromorphology (Mo et al, 2010;José et al, 2020), permeability (Huajun et al, 2013;Ghofrani and Plack, 1993), etc. However, the studies are scant regarding the rheological characteristics of incorporating magnesium oxide particles into oil-well cement slurry.…”