Potassium chloride (KCl) is typically used in the formulation of cement spacers to inhibit the shales from swelling and dispersion. It serves as a shale inhibitor during cementing operations to ensure good wellbore integrity. To obtain optimum inhibition, a high concentration of KCl might be required. A massive amount of potassium chloride will lead to a negative impact on the environment, cement slurry setting time, and wireline logging methods. This work aims to design and synthesize a novel inhibited cement system with an improved shale inhibition performance and wellbore integrity without harming the ecosystem.

A spacer and cement formulation utilizing a novel mixture of different high molecular weight polyamines have been prepared successfully and compared against conventional formulations. Our study includes dispersion testing using representative shale samples and spacer compatibility with water-based drilling fluids and cement. The compatibility investigation included rheology testing, thickening time testing, compressive strength measurements, and free water tests.

The study shows that KCl concentration should be monitored carefully to avoid cement immature settings. KCl salt also resulted in improper wellbore integrity due to its low performance in shale inhibition compared to amines. Amines did not result in retardation nor acceleration of cement setting. Representative shale dispersion with cement filtrates and spacers show a high dispersion recovery factor of 96.5%, with the novel polyamine additive compared to 82% with potassium chloride.

We illustrated detailed experimental and field applications of a novel mixture of different high molecular-weight polyamines. Contrary to conventional KCl, the new formulation resulted in improved shale inhibition and enhanced wellbore integrity. The value of this study was further validated by the successful execution of cementing a casing installed in a water-sensitive shale formation.

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