Abstract
The primary cement of oil and gas wells is prone to fail under downhole conditions. Thus, a remedial operation must be conducted to restore the wellbore integrity and provides zonal isolation. Many types of materials are currently used and/or have the potential to be employed in wellbore integrity applications, including, but not limited to, conventional Portland cement, microfine and ultrafine cement, thermoset materials, and thermoplastic materials. In this study, several types of materials were selected for evaluation: (1) conventional Portland cement, which is the most widely used in remedial operations in the petroleum industry, (2) polymer resin, which is one of the most recent technologies being applied successfully in the field, (3) polymer solutions, and (4) polymer gel, which is a semisolid material that has shown potential in conformance control applications. This work addresses injectivity and the parameters that affect the injectivity of these materials, which to the authors' best knowledge have not been addressed comprehensively in the literature. The results of this study demonstrate the effects of several factors on the injectivity of the sealants: void size, viscosity of the sealant, injection flow rate, and heterogeneity of the void. The results also promote the use of solids-free sealants, such as epoxy resin, in wellbore remedial operations because epoxy resin behaved like Newtonian fluid and can therefore be injected into very small voids with a minimum pressure requirement.
Highlights
During the life of oil and gas wells, the wellbore cement is subjected to numerous types of failures, with many causes, as addressed by Alkhamis and Imqam (2021)
Prior to any remedial operation, an injectivity test, using solids-free fluids, is conducted to determine some of the parameters required for secondary cementing as this operation requires a careful analysis
The epoxy resin behaved like a Newtonian fluid Fig. 2b, where no stress or only a very small stress was required to initiate flow, and the viscosity was independent of the a b
Summary
During the life of oil and gas wells, the wellbore cement is subjected to numerous types of failures, with many causes, as addressed by Alkhamis and Imqam (2021). The failures may occur due to insufficient mud removal before the cementing operation, improper hydrostatic pressure delivered by the cement slurry during the primary cementing operation, casing expansion and contraction, and/or post-cementing causes, such as high-pressure tests and high-temperature variations during production (Thiercelin et al, 1998; Alkhamis and Imqam, 2018). Whether these failures occurred during drilling and completion, production, or even after abandonment, a remedial cementing job or “secondary cementing” operation is performed to restore the wellbore cement integrity. This analysis includes estimating the significance of the problem, evaluating the associated risk factors, selecting the proper sealing material, choosing the placement technique, and assessing the economic costs
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