While downhole chemical squeeze treatments are common practice for deploying scale inhibitors to protect wellbores and downhole production tubulars from inorganic deposits, their adoption for corrosion inhibitor treatments (CISQ) is much less commonplace. Historically they have often not been considered an option due to either anticipated poor lifetimes or the risk of formation damage in the form of emulsion blocks, wettability changes or relative permeability modification. However, in a number of carbonate reservoirs producing from different regions, corrosion inhibitor squeeze treatments have been shown to provide corrosion protection for downhole production tubulars when no alternative downhole chemical deployment technique is available.

This paper will present a technical review of the potential benefits of CISQ treatments. Different inhibitor retention/release mechanisms in sandstone and fractured carbonate reservoirs will be discussed, including classic adsorption/desorption and chemical imbibition/diffusion, as will the impact of these mechanisms and oil/water partitioning behaviour on squeeze lifetimes. Another factor limiting adoption of CISQ treatments is the misconception that residual assay techniques may be inadequate, and we demonstrate that this is not necessarily the case.

In addition to providing a mechanistic interpretation of the available retention and release mechanisms, the results of laboratory core flood studies will illustrate the different retention mechanisms and offer the potential to achieve considerably different lifetimes with different types of corrosion inhibitors. Field examples will also be cited in support of this. In these cases, the accuracy of the measured residual corrosion inhibitor return concentrations were confirmed by conventional electrochemical corrosion inhibitor performance measurements.

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