The present paper describes performance improvements and well safety achieved with the use of Managed Pressure Drilling (MPD) in the exploratory block of Parva Negra Este, in Neuquén Basin. Petrobras Argentina S.A (PESA), with the technical support from the Petrobras’ headquarters, in Brazil, drilled two exploratory wells applying MPD and targeting Vaca Muerta shale oil & gas play. High-pressure zones characterized the drilling scenario, reaching, usually, pore pressures higher than 18 lbm/gal in unconventional reservoirs, composed of tight sand and shale. The use of MPD in both well constructions was quite efficient, including well control and plug and abandonment (P&A) operational applications. Those operations proved that MPD can effectively replace the Under-Balanced Drilling (UBD) system, which is standard practice in that area. In the first well, PESA reported significant gains in drilling performance when compared to other wells previously drilled. Drilling with MPD did not record non-productive time (NPT), differing substantially from the previous wells constructed in the surroundings of Parva Negra Este with an average NPT of 20 days. A considerably larger recovery of coring samples was achieved, being also possible to eliminate one well section, by drilling two zones of interest in a singlesection. Additionally, lessons learned were implemented, resulting on higher rate of penetration (ROP) with the support of MPD. In the second well, a high overpressurized pore zone was reached, leading to a very complex well control event followed by a permanent P&A operation. The formation pore pressure was much higher than the expected for the area. Instead of using an 18 lbm/gal drilling fluid, it was necessary to weight the fluid up to 21.3 lbm/gal, adding hematite as weighting material. In that scenario, the use of MPD made the operations of circulation and well cementing safer than with the conventional drilling approach utilized in that vicinity. The application of Dynamic Formation Integrity Tests (DFIT) and Dynamic Pore Pressure Tests (DPPT) ensured a more precise operational window, helping to formulate risk matrices for safely pulling the drilling string out of the hole. In addition, the precise definition of the operational window was a valuable information to plan the best approach for P&A. Besides performing those tests, the MPD system was very useful to evaluate operational parameters and verify how effective was the settlement of the abandonment cement plugs. In summary, MPD supported safer drilling and P&A jobs, better drilling performance and greater information achievement through more efficient well logging and sample coring.

The objective of this paper is to describe the well management process which includes the design methodology and the well execution procedures utilized by Petrobras International to drill its first ultra deepwater well in a remote and challenging area of the Turkish waters in the Black Sea.Ranked as a well of the highest complexity level, the drilling of this wildcat deepwater well has faced a number of expected hazards such as the presence of shallow gas zones, long abnormally pressurized intervals, low fracture pressure gradient sections, loss circulation zones due to the presence of fractured limestone, great potential for false kicks (breathing formation and ballooning) and the possibility of having gas migration to the riser.In addition to the risks listed above, the well location, in the middle of a remote area of the Black Sea, has been also considered a great challenge in terms of operational logistics. This came from the fact that Petrobras had to plan all its operations from scratch, including moving a huge semi-submersible drilling rig under the bridges located on the Bosphorus Strait.In this work it is also presented the Well Classification Methodology developed by Petrobras. Such method takes into account several factors that includes water depth, number of well drilled in the area, the existence of abnormally pressurized formations and a number of other obstacles. The main idea of this procedure is to establish the proper well design robustness and to define operations actions which should be used to mitigate operational problems that could arise.Despite of all these challenges, the well was executed according to its original plan indicating that the methodology was successfully applied and can be repeated in other wells. A number of lessons learned during the planning and execution phases of this project are also discussed within the scope of this work.