Schlumberger

Technical Paper: Use of Surfactant in Cement Slurry to Mitigate Incompatibility with Synthetic-Based Drilling Fluids

Society: OTC
Paper Number: 27902
Presentation Date: 2017
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Abstract

In deepwater Gulf of Mexico, the use of synthetic-based drilling fluids (SBM) is common practice in all types of wells drilled by different operators. These fluids have been under constant development in past years. However, even with the latest in SBM technology, cementing operations can be adversely affected when this type of fluid is used, which can compromise the quality of the cement jobs. One of the challenges faced is the rheological incompatibility between the cement slurry and the SBM. This may lead to issues such as induced losses during primary cementing operations, due to higher friction pressures, or stuck pipe during plug placement, among others. The higher friction pressures during cement placement in primary jobs can also lead to an inaccurate or inconclusive post-job evaluation when attempting to match software-simulated pressures with actual pressures acquired during the jobs. Despite the use of mechanical separation and spacers, the post-job analysis of several recent cement jobs suggests that contact between cement slurry and drilling fluid is often still occurring. As expected, this contact is most frequently occurring in the annular space wherein there is typically an absence of mechanical separation. In these jobs, laboratory test results using mixtures of slurry and SBM with various ratios have shown levels of incompatibility, which have been correlated to evidence of higher-than-expected friction pressures in the same jobs. The solution proposed for this scenario is to add surfactant or surfactant-based chemical additives at low concentrations to the cement slurry. The addition of surfactant to cement slurries has been proven to reduce rheological incompatibility between the slurry and SBM and the impact of contamination on set cement properties. This paper presents the laboratory test results, operational concerns, mitigation, and a case study showing the application and effectiveness of this technique comparing similar strings that were cemented in different wells.

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