The ambitious plan to develop and produce the prolific Pre-Salt reservoirs in the Brazilian Santos Basin was kicked off by the discovery of the gigantic Lula Field in 2006 (previously known as "Tupi"). For Petrobras, the first decade of this century was therefore marked by the significant challenges imposed by these complex carbonate reservoirs, requiring the accelerated introduction of new technologies and innovative approaches to well construction. This article describes the history of well construction in the offshore Brazilian Pre Salt area. It summarizes the evolution in well design that resulted from the implementation of innumerable "lessons learned" that were acquired since drilling of the first wildcat well in the Pre-Salt Cluster. The commulative experience of more than 100 wells drilled and 29 wells completed (to date), has resulted in a progressive reductions of time and CAPEX required for the construction of the development wells in the Santos Basin.

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.

In recent years, PETROBRAS has been using MPD (SBP/MCD) technology in ultradeepwater scenarios at development and exploratory wells. Although MPD techniques are an advance over conventional drilling, it also brings more complexity to the operation and, in some cases, increases the duration and costs of the interventions when compared to conventional drilling. Ideally, the rigs equipped with MPD system should only be used in wells, or in specific phases of the well, that requires MPD to conclude or where the NPT associated with fluid losses is considerable. In these scenarios, the extra costs and extra time necessary are negligible, compared to the NPT avoided, and the alternative would be not to reach target depth or drill the well. Geomechanics, pore pressure estimation and loss zone identification are not an exact science. There is always an uncertainty in predicting MPD (SBP/MCD) demand, pushing the development of techniques and strategies to optimize the allocation of MPD rigs in wells where the NPT would be so high that the use of the MPD is advantageous, or, where MPD is an enabler of well construction. This paper describes a probabilistic analysis developed to support the determination of MPD (SBP/MCD) demand, calculating the optimum number of rigs to be equipped with MPD (SBP/MCD) and RCD system, and which intervention strategy is the most cost effective for a development campaign, based on historic results.

The development of the production phase of pre-Salt fields in Santos Basin have been facing many challenges, one of them is the occurrence of massive fluid losses during drilling, completion and evaluation operations. One possible solution to drill in this scenario is the usage of the Managed Pressure Drilling (MPD) techniques to minimize fluid loss and, in cases of massive losses, the use of the Mud Cap Drilling technique. This paper presents a case study of the drilling operations on a Santos Basin well that had major losses while using conventional drilling technique hence unable to reach all objectives. The well was successfully reentered using MPD/PMCD to successfully reach target reservoir and the details of the solution to reentry using MPD/PMCD and its successful results is presented It is described the use of MPD variants including the first use of PMCD on a DP rig on an offshore well in Santos Basin. MPD/PMCD proved an enabling technology when reentering a reservoir with major losses and absent drilling window. Design, execution and results of successful operations are covered.

Summary The demand for ultradeepwater scenarios invoked the frequent application of managed pressure drilling (MPD) in the last few years. In an ultradeepwater scenario, oil companies face issues such as narrow pressure windows and severe loss zones. Many wells are considered undrillable without the aid of MPD technology. MPD operations need to be correctly evaluated with consideration given to increased time and cost/benefit analysis. In this paper, we propose a probabilistic model to evaluate MPD demand by estimating the optimal number of rigs equipped with MPD and a rotating control device (RCD), and we analyze which intervention strategy is the most cost– and time–effective. Reducing uncertainty is an important factor when making decisions about drilling. We adopted a Monte Carlo simulation using loss–zone estimation, probability of prediction error, the number of rigs equipped with MPD, and several strategies. Better MPD strategies were determined on the basis of available data and the optimal number of rigs equipped with an MPD system and RCD equipment, reducing subjectivity in the decision–making process. The originality of our paper lies in the new quantitative approach to dealing with uncertainty in the prediction of fluid losses and the cost and duration of different MPD strategies, numerically simulating the possible scenarios.