Over the past decades, the oil-well cement (OWC) has been used in sealing the wellbore-casing or inter-casing annular spaces. The Microbial-induced precipitation (MIP), on the other hand, is an emerging biomineralization cement system that can be utilized in energy, construction, mining, and other industries. However, understanding the mechanical integrity and peak strength of these cement systems are important for improving their applicability at varying in-situ-pressure and temperature conditions. Here, we experimentally investigated the mechanical integrity of the microbial-induced precipitation and the oil-well cement and their applicability to plugging of leakage pathways. We utilized 2 core samples from a sedimentary sequence with artificially induced fractures along the longitudinal axis of the cores, and treated the induced-fractures in these cores with the cementations from the MIP and OWC, respectively. We compared the mechanical properties of the cement seals in these cores to assess their mechanical integrities and applications. Our results show that the OWC is more efficient than MIP in sealing in-situ macro-fractures and provided a relatively greater mechanical integrity for the wellbore-casing or inter-casing annular spaces. In addition, although OWC has higher mechanical integrity over MIP, the MIP has an edge in its application for sealing of microfractures and mini-aperture of casing-cement or cement-formation delamination. We envisage that our study will advance the understanding of these methods and their applications for the enhancement of wellbore integrity for drilling operations, enhanced geothermal systems (EGS), geologic CO2 storage (GCS), and mining operations.

1 Introduction

Well cementing operation is the process of introducing cement slurry to the annular space between the wellbore and casing, or the inter-casing annular space (Anya et al., 2019, 2020; McElroy et al., 2020, 2021). Traditionally, oil-well cement (OWC) is used to repair wellbore integrity issues and leakage pathways developed during well completion or post-completion processes. In wellbore construction operations for oil and gas wells, geothermal wells, CO2 injection wells, and mining wells; the oil-well cementing (OWC) method has been utilized over the past decades in protecting the casings from corrosion and providing mechanical support, hydraulic seal, and adequate zonal isolation for the wellbore-casing or inter-casing annular spaces.

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