Infuence of depth on induced geo‑mechanical, chemical, and thermal poromechanical efects
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Date
2021-05-14
Journal Title
Journal ISSN
Volume Title
Publisher
Journal of Petroleum Exploration and Production Technology
Abstract
Delivering efcient and cost-efective drilled and excavated holes require efective prediction of instability along the hole
profle. Most drilled and excavated hole stability analyses in the literature are performed for a given zone without considering
the infuence of depth. This study focused on determining the infuence of depth on induced geo-mechanical, chemical, and
thermal stresses and strains in drilled or excavated holes. To this end, a new porochemothermoelastic model was developed
based on extended poroelastic theory, and the developed model was employed in determining induced strains and stresses
for an oil and gas well case study, using data from the literature. The study delineated the diferent signifcance levels of
geo-thermal-, chemical-, and thermal-induced strains and stresses as depth increased. From the results obtained, it was clear
that at shallow depths, chemically induced strains and stress were the most signifcant formation perturbations responsible
for instability of drilled and excavated holes. On the other hand, at deeper depths, geo-mechanical-induced strains and stress
were the most predominant. Comparatively, thermally induced strains and stresses were found to be the least signifcant
formation perturbations responsible for instability of drilled and excavated holes. For this case study, the results indicated
that chemical strains and stresses were more prominent at depths below 170 m, accounting for more than 50% of the total
stresses and strains. At 170 m, both chemical and geo-mechanical stress and strain had equal contributions to the overall
stress and strain. However, as depth increased, the percentage contribution of the geo-mechanical component increased and
accounted for about 80% of the total strains and stresses at 1000 m, which increased to 98.48% at depths of 6000 m and
beyond. The fndings of this study will provide guide for future studies on the application of extended poroelasticity theory
in solving instability problems of drilled and excavated holes.
Description
Keywords
Stress, Strain, Poroelasticity, Porochemothermoelasticity, Borehole stability, Ogbonna F. Joe, CFOREM, Université de Ouaga