Evaluation of Drilling and Completion Techniques Used In 10 Years of the Deepwater Marlim Field Development

Abstract

Abstract Marlim field, discovered in December 84, with a total area of 132 square Km lays in water depths from 650 to 1,050 meters. First oil came on stream in 1991 with the vertical well 3 MRL 3 RJS at 721 meters of water, after the development of guidelineless subsea hardware as well as other technologies to allow production in deepwater. The main idea, still in use these days, was to develop the field with simple drilling and completion projects. The water depth, highly friable sandstone and high costs in deepwater drilling and completion were some of the obstacles to be overcome. During the field development, the better knowledge of the reservoir, as well as other innovative drilling and completion techniques in deepwater, allowed a higher production of the wells. A total of 129-production and water injection wells either vertical, directional or horizontal will be on stream in Marlim and many lessons were learned along the last ten years. The best practices for drilling and completion were implemented not only in Marlim but also in other offshore developments in Brazil. This paper will present the drilling and completion techniques used in Marlim field development and show how these techniques contributed for the production increase. Although the field development is close to the end, new well designs are being studied to be implemented thus confirming the importance of Marlim field as the most important laboratory for deep and ultradeep water development. Moreover future challenges for workovers will be anticipated. Introduction Deepwater drilling offshore Brazil started in 1984 when a conventionally moored drillship drilled the well 1 RJS 287 at 501 meters water depth (WD). In the same year, the first dynamic positioning (DP) drillship contracted by Petrobras also started an exploratory campaign in Campos Basin. The first well drilled by this DP drillship, the 1 RJS 219 A at 853 meters of water stroke oil in December 84. The tests performed in February 85 showed an unconsolidated sandstone reservoir with permeability of 2 Darcies and high gravity oil (ranging between 17-21 API). Further drilling and appraisal activities confirmed a total area of 132 square Km with oil in place of 9.0 billion barrels. An appropriate name then was given to this discovered giant field: Marlim. (Fig 1) Other fields named Marlim Sul, Marlim Leste and Voador fields were also discovered during the delimitation period of Marlim field. The productivity index (PI) of these wells reached up to 300 m3/day/kgf/cm2 and sand production demanded adequate control mechanisms. By 1989, ten wells had been drilled in the Marlim Complex and the main problems to drill wells in deepwater were being surpassed year after year, but production at such water depth was still challenging. Several alternatives to exploit Marlim field were analyzed but all of them impaired restrictions.