Fluid losses are still today one of the most challenging problems in well construction. The scenarios faced by operators during development and exploratory campaigns in the deep water pre-salt area are characterized by natural fractures, vugs and caves. Therefore, problems related to loss of circulation are critical, increasing the non-productive time and consequently, well construction costs. Additionally, in several situations, conventional drilling limitations prevent the reaching of the well target. The present study proposes the application of a methodology to define optimum loss control material (cross-linked pills, fluid loss squeeze, bridging agents, cement), among those available for each situation, to minimize lost circulation events during drilling operations. An Artificial Intelligence strategy based on Supervised Learning was defined to generalize data collected from five hundred lost circulation events over a three years period. Human Computer Interaction principles were used on the development of an interface where the field engineer can interact with training data while having little to no Machine Learning knowledge. The use of empirical analysis and learning strategies as tools to assist the decision making process in the form of lost circulation countermeasures is described by this paper. The method was validated on data collected from several different wells in the Santos Basin, Brazil, pre-salt area. The strategy was already applied in two real cases resulting in a six days well construction time saving.

MPD is a very powerful tool that is gaining momentum for deepwater offshore wells construction. A dynamic positioning rig adapted to MPD operations can apply different techniques that better suit to each well scenario. Currently Petrobras has over 20 MPD deepwater offshore wells drilled, having applied different techniques to achieve success: from "basic" SBP to MCD variants. This paper discusses the various MPD techniques that can be utilized from a dynamic position rig during deepwater well construction.

Drilling fluids play great importance to the success of MPD (Managed Pressure Drilling) and MCD (Mud Cap Drilling) operations. On MPD projects, the correct design of the drilling fluids properties, such as, density, rheology, anchor point position and compatibility should be precisely adjusted in order to operate in good and safe performance, especially in a statically underbalance MPD projects. Exceptional importance should be addressed to the initial mud density to provide useful capacity to carry out a Dynamic Porous Pressure Test (DPPT). MCD operations require a suitable drilling fluid project due gas migrations, costs and cuttings transportation issues, related to LAM (light annular mud) and sacrificial (SAC) fluids. The objective of this paper is to present the lessons learned in drilling fluid projects during MPD and MCD operations in Brazil's offshore wells. The study will focus on desired properties, simulations, adjusted hydraulics models, formulations and involved costs, considering water and olefin based drilling fluids.

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