Coiled Tubing Becomes the Key Enabler for Successful Multilateral Well Development Campaign Offshore Brazil

Abstract

Pampo was among the first producing fields offshore in Brazil, and it produced through a fixed platform. The maturation of the field and consequent decrease in oil production required a different completion strategy for the operator. The key reservoir, the Macaé/Quissamã, is the prime target for exploitation because it still has substantial oil in place, with good total recovery and actual recovery factors. The development of this reservoir was vital to the survival of the field. Several technical issues exist for developing this reservoir, especially during drilling, because of the high density of wells in the area. Each new well had to be carefully planned to avoid collision with existing wells and also to optimize the reservoir drainage. Several depleted wells have been evaluated to determine whether they should be abandoned and/or substituted. There were limited options for replacing these depleted wells. With collision problems at shallow depth looming as a huge risk, the number of new wells that could be drilled was low. Furthermore, the lack of rigs available for production drilling and the high slot utilization on these platforms provided additional complications. Ultimately, the development of multilateral wells was identified as the most viable solution. From the main bore, once past the critical collision zone, several legs could be drilled to increase the drainage area. Multilateral construction in this scenario is a nontrivial task. It requires the well junction to be placed at an area of high deviation, adding complexity for any intervention work. Nonetheless, the use of coiled tubing for most of the well completion operations proved to be the key enabler in this successful multilateral well development campaign. The versatility of CT technology significantly decreased the time needed for well completions and its other applications. This paper discusses the development, planning, and preparation activities involved with use of the CT in this milestone project. It summarizes the results of the development of the idea and lessons learned from the numerous runs during the completions operation, including CT-conveyed perforating; CT-conveyed logging for cement evaluation; stimulation, featuring the use of isolation tools; and several Stiffline applications. Introduction During the conception phase of this project there were many obstacles that needed careful attention:The position of the ML Junction at a near-horizontal position required the use of CT for a set of tools designed to be used with SlicklineThe changes in the project with the scaling down of the tool in order to fit Petrobras's existing 4" configuration presented a last minute challenge, with many tools being changed to allow for the access to the main bore or the later leg of this ML System. This ML System was designed to be used in a 5" Bore configuration.Given the rig's age, the crane capacity has been scaling down considerably over the years, even during the project execution, with a maximum limitation of 18 tons. Obviously this restricted the use of larger CT diameters, and even with the minimum amount of CT in the reels it was impossible to place the CT Reel on a position to execute these wells were the slots were placed in relation to the crane's maximum reach.The notion that CT was to be used as the main tool to allow wellbore access and to perform the majority of the tasks downhole posed a conceptual challenge, as in general there were not many people within the Client organization who felt CT was the way to execute these tasks.CT Perforating with high angle and large OD Perforating Guns presented a CT damage possibility due to the shock wave travel that could happen during the detonation. Field Description Pampo, located at south part of Campos Basin, is an offshore location, 80 km far from the coast and 105 m water depth was discovered in 1977.