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Assuming horizontal bedding inside the formation and contemplating the affect of bedding planes, the variation of wellbore collapse tension polar plots with development drilling time in shale formations is illustrated in Determine 8. Analysis reveals that When thinking about the affect of bedding planes, the adjust in collapse force for small-angle wellbores is comparatively smaller, even though for high-angle wellbores, the collapse strain noticeably will increase.
Based on uniaxial compressive toughness experiments with distinct bedding angles, shale toughness reveals substantial anisotropic characteristics.
Coupled with logging information, the modify regulation of formation caving tension is analyzed and formation force is predicted. The analysis reveals that the oil shale rock During this region has lower toughness, the Main is hard and brittle, plus the Main is anisotropic underneath the impact of bedding. The strength weakening law of oil shale soaked in oil-primarily based drilling fluid is analyzed, plus the development collapse tension variation regulation is additional obtained. The fracture stress, caving stress and pore strain with the proposed drilling are predicted, which presents technological aid for the Secure and effective drilling of shale oil drilling inside the South China Sea.
This paper develops a computational program to work out the lower limit of your safe density window for shale formations and investigates the influence of shale toughness anisotropy and hydration time on the safe drilling fluid density window.
According to the weakening model of shale power with hydration time, the weakening craze of shale overall body and bedding airplane toughness with hydration time is illustrated in Determine three. It might be noticed that with increasing hydration time, the strength of shale at first decreases swiftly.
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e., drilling up dip together the bedding plane is much more conducive to wellbore stability; maximizing sealing to cut back filtrate invasion in the development; adding inhibitors on the drilling fluid to lower its activity; employing oil-dependent drilling fluids to suppress rock hydration.
Research of wellbore instability in shale development looking at the influence of hydration on power weakening
Based on the experimental study On this paper, it is thought the Jaeger single weak plane criterion, that is expressed as Eq. 4, can better expose the toughness of various shale layers with varying bedding angles (Ma, 2015; Ma and Chen, 2015; Yang et al.
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, 2017). Nwonodi et al. (2023) proposed a time-dependent analysis technique for predicting wellbore instability in horizontal wells within reactive shale formations. By integrating osmosis/diffusion concepts, the review improved conventional designs that neglected membrane failure and diffusion time consequences. The Mogi-Coulomb criterion was launched to systematically incorporate factors which include membrane effectiveness degradation, rock power reduction, and ion migration. Junyang et al. (2017) conducted acoustic emission experiments to the hurt and failure process of laminated shale less than uniaxial compression, finding out the mechanisms of damage and deterioration beneath the influence of bedding and h2o. The outcome indicated which the hurt mechanisms differ; bedding principally triggers damage from the distribution of Major microcracks together the bedding planes, although h2o-induced hurt predominantly stems from adsorption and capillary strain. Wang (2019) analyzed the changes in shale Bodily properties beneath distinctive hydration problems and modified the wellbore stability analysis model to account for hydration results. For many in situ tension distributions, the review analyzed wellbore stability, indicating that collapse pressure raises appreciably in the early phases of hydration and the rate of raise slows down as time passes.
Prolonged drilling time weakens bedding planes, escalating the chance of shear sliding failures. These conclusions enhance our capability to evaluate hydration’s influence on wellbore stability quantitatively.