Abstract

Geo-mechanical analysis and ensuring wellbore stability are paramount for the success of deep geo-energy production projects. The present study addresses the complex challenges arising from geological formations comprising laumontite-rich rocks, fault zones, and fractured rock formations, which significantly influence the mechanical behavior and stability of wellbores.
Tight glutenite reservoir formations containing laumontite minerals pose challenges for geo-energy production due to their complex stress-sensitive mechanical behaviors. With an increase in the confining pressure, there is a transition from the shear dilation to the consolidated compaction in laumontite-rich formations. This study presents the finite element modeling of constitutive behaviors of laumontite-rich rocks using a thermodynamic-consistent plasticity model. Poromechanical analysis is performed to investigate plastic zone development around a borehole in an overpressured reservoir along with a comparison to traditional plastic constitutive models. The findings contribute to understanding and addressing the challenges of wellbore stability in laumontite-rich formations for geo-energy projects.
The wellbore stability of deeply buried petroleum wells in fault zones is another major concern of deep drilling projects. This study also focuses on a super-deep petroleum well drilled into an Ordovician limestone reservoir formation with a buried depth of about 8000 meters located in the Tarim Basin, China. Laboratory tests and dual-porosity theories of poromechanics are employed to derive stress and pore pressure distributions in a limestone formation surrounding the wellbore. The analysis highlights the significance of borehole azimuth and the selection of an optimal well trajectory, considering the strength properties of both the rock matrix and fractures.
Geological formations in the Canadian Shield with natural fractures in fault zones offer enhanced permeability for geothermal development. However, ensuring wellbore stability during drilling and energy production is crucial. The Finite Element modeling is employed to assess the performance of boreholes in fractured rock formations under non-isothermal conditions at a potential deep geothermal site in northern Canada. The analysis considers plastic yielding in the rock matrix and sliding potential along fractures, accounting for the cooling effect. Findings highlight the importance of managing the cooling effect to avoid excess pore pressure build-up and sliding along tilted fractures.
Collectively, this research provides a comprehensive understanding of wellbore stability and geomechanical behaviors in diverse geological formations. The findings contribute to the development of strategies and guidelines for safe and efficient geo-energy production in challenging geological environments.