Abstract

Production liner cementing operations are critical due to the small cement slurry volume, the requirement to achieve good mud removal in narrow annuli and, in most cases, the need to pull the running tool out of cement at the end of the operation. The risk is increased when the operations are conducted in deepwater environment, because there is increased complexity in predicting the actual bottomhole circulating temperature due to the long water layer acting as a heat exchanger for the wellbore fluids.

In deepwater environment the cement slurry suffers different heating and cooling stages, such as being heated up when batch mixed, cooled down when passing through the riser-seawater section and heated up again when sent downhole. To avoid any problem after retrieving the running tool and landing string, a synergy between the operator and service company brought an improvement to laboratory testing procedures. Non-API laboratory tests for cementing liners were developed in Brazil using temperature simulators reproducing the planned operations and performing sensitivity analysis for additives concentration, fresh water content variation, slurry density variations, contamination effects and bottomhole circulating temperature changes.

These practices allow the operator to evaluate cement slurry behavior under a number of conditions that could otherwise cause major job failure or even loss of a well. This document describes in detail the procedures that significantly decrease the risks associated with liner cement jobs and the high costs related to failures in deepwater operations. Since the implementation of these measures, the operator has not experienced any liner cement job failure related to cement slurry design.

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