A Specially Designed Organophilic Chloride-Free Reservoir Drill-In Fluid Meets the Challenges of the First Horizontal Well in Mozambique

Abstract

An operator was planning to drill the first horizontal well in the Inhassoro field in Mozambique. The type of completion would be an open hole utilizing expandable screen technology. The formation had highly reactive shale stringers necessitating the use of an inhibitive fluid, but due to the environmental restrictions, the use of non-aqueous fluid systems could not be used to drill or complete the horizontal section. The issue of cleaning up the filter cake was examined as it would be confined with the use of the expandable screen. Normally a breaker system would be required to cleanup or disperse the filter cake with this type of completion; but due to the water sensitivity of the reservoir, any aqueous filtercake breaker would have to be left out of the completion process.The reservoir drill-in system used to drill horizontal section would require an inhibitive water-based fluid that was also chloride free due to possible contact with the ground water. The system would also require a filter cake that could be cleaned up with the producing hydrocarbons due to the absence of any filtercake breaker system. The filter cake must also demonstrate a low permeability in order to limit the invasion of fluid into the sensitive formation. A low coefficient of friction would also be another requirement for the reservoir drill-in system. This paper will highlight the design optimization, the unique characteristic, the testing and the successful implementation of this special reservoir drill-in system.