In line with the rise in remote deepwater exploratory work in East Africa, a major operator drilled a well in one of the two petroleum block licenses that they own offshore Kenya. The well was drilled in a water depth of 723m (2372ft) with the primary objective of establishing the presence of net pay and fluid type at specified stratigraphic levels. Prior to spud, the geological prognosis of the well indicated the presence of carbonate formation characterized with vugs and the imminent risk of severe losses were predicted. The drilling of this well indeed proved to be a challenging process. Lost circulation while drilling and cementing continues to be a consistent problem in most deepwater operations that costs significant time and money. Firstly, the operator is faced with the inability to reach planned total well depth within the projected time interval, and secondly the necessary hydraulic isolation (cementation) covering problematic formations is not achieved. In addressing the loss and weak zones, different approaches are used notably by reducing the hydrostatic pressure column, utilizing lighter weight slurries and reducing the penetration of fluids into fractures with the use of lost circulation material. Losses were encountered in all hole sections below the 20-in casing just as predicted; estimated between 40 to 180 bbl/hr. As per a planned line of action, the mud service company pumped a range of lost circulation materials with different formulations, but none was successful. The executed approach was not effective in curing the losses and this resulted in total down time of 16 days of rig time causing the operator an additional $20 million over the AFE. Out of this additional cost, $0.34 million was due to mud lost into the formation and the rest was for daily operating rig cost. The extent of the losses was so severe that it took a total of three engineered fiber pills and cement plugs placed at different depths before the operator could drill beyond the troubled zones. This paper is intended to cover the use of an engineered fiber and solids technology in a spacer system that was pumped ahead of cement slurry to aid in curing the losses.
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