Abstract

Cementing a wellbore is a major stage in well completion and an initiation for production operations. One of the primary objectives of the cementing operations is zonal isolation. For effective zonal isolation and optimum hydrocarbon production during the life of the well, the entire drilling fluid, which presents in the annulus between the hole and the casing, should be removed. Over the years, several practices have been employed to help achieve mud removal and successful zonal isolation. From industry practices, efficient mud removal can be achieved with the use of spacers and flushes before cement is placed. The spacer system is designed according to different conditions including geological condition of the well. With the increasing tendency to drill high-pressure high-temperature wells, the design of robust and stable spacers is becoming more critical. Various spacer systems are available, but they may not be suitable for these conditions. The efficiency of spacer system is largely dependent on the rheological properties of the spacer at elevated temperatures. In this paper based on the laboratory investigations, the performance of specially designed spacer systems, their compatibility with mud systems and mud removal efficiency are compared in various temperatures. The spacers are weighted spacers, which are specially designed to meet the existed geological conditions of the well. The spacers contain a suitable surfactant package to increase its surface cleaning ability, a weighting agent (e.g. hematite) to adjust the spacer's density and a rheological modification agent. The proportions of these components in a spacer system will control the rheological properties of the final mixture, and thus, performance of the spacer. The spacers systems show a reliable performance in a wide temperature range.

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