The interaction between injection performance and borehole integrity is of interests to injection operations decisions. This paper presents an elastic effective stress solution for a borehole with uniform filter cake, which was modelled using a reduced permeability layer of constant thickness. We evaluated effects of filter cake on borehole integrity for two well operating conditions of (a) constant injection pressure with increasing skin (decreasing injectivity), and (b) constant injection rate with increasing skin. Results confirmed that the stress path was mainly dominated by the magnitude of injection pressure. Wellbore failure was more likely to occur in a constant injection rate with increasing skins. To emulate the effect of non-uniform filter cake clean-up on wellbore integrity, we evaluated the influence of placing impermeable filter cake at different positions around the borehole. Suggestion on how to reduce wellbore failure was also provided.

1. INTRODUCTION

Fluid injection technique is used extensively in water flooding (Craig 1971; Morrow and Buckley 2011), produced water re-injection (van de Hoek et al. 2000; Van den Hoek et al. 1996), hydraulic fracturing (Fu et al. 2020; Guo et al. 2017; Luo et al. 2019), CO2 injection and storage (Liu et al. 2017; Mishra et al. 2017), nuclear waste disposal (Alexander et al. 1996; Moore, Morrow, and Byerlee 1982), etc. Due to poroelastic effects, the fluid injection operation changes both reservoir effective stress and total stress; thereby, inducing rock failure potentials (Guglielmi et al. 2015; Wang et al. 2015). Injectors also encounter injectivity decline caused by near wellbore impairment (Bachu and Watson 2009; Golovin et al. 2011; Sharma et al. 2000). How impairment impacts borehole failure is of interests to injection operations. For example, is the borehole becoming less stable when injectivity declines while the injection pressure remains constant? Or the borehole is more stable by maintaining a constant injection rate as the injectivity declines by increasing the injection pressure? These injection operation questions highlight the need to study the interaction effect between well impairment and borehole stability.

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