The benefits of formation pressure testing while drilling include improved formation evaluation, drilling hazard mitigation, drilling performance optimization and saving time. In deepwater wells offshore Angola, this is regularly used in 12 ¼-in. and smaller hole sections. The requirement extended to the 17 ½-in. hole sections which are typically directionally drilled with high buildup rates due to the reservoir being located at a relatively shallow depth below the seabed. The plan was to adapt the formation pressure testing equipment already used in 12 ¼-in. hole and establish a technique to use it in 17 ½-in. hole. This was complicated by the high buildup rates in the 17 ½-in. hole, as opposed to the high-angle tangents seen in the 12 ¼-in. hole sections. The unconsolidated nature of the formation further complicated the process as the low compressive strength of the rock can prove challenging for directional steering and the friability of the formation could affect both the seal of the formation pressure tester and its ability to sample pressure.

This paper will discuss development of the techniques over the initial wells, issues that were encountered and solutions developed to simultaneously deliver the formation pressures and the directional profiles using standard equipment. In addition, the paper will discuss how the techniques developed for the 17 ½-in. hole were further adapted to sample formation pressures when these had to be measured in 13 ½-in. hole below 9 ⅝-in. casing in situations where conventional formation pressure testing techniques could not deliver data. As a result, the paper describes the successful deployment of real-time formation pressure testing in large hole sizes whatever the directional challenges.

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