Atlanta Field: Developing Heavy and Viscous Oil in a Challenging Environment

Abstract

Abstract Atlanta is a post-salt oil field located in the original Block BS-4 ring fence, 185 km off the city of Rio de Janeiro, in the Santos Basin, Brazil, under water depth of approximately 1550 m. However, Atlanta Field is not just another ultra-deepwater project; for its development, several other challenges shall be overcome, such as the low burial depth, its highly unconsolidated sandstone reservoir, the heavy and viscous crude flow assurance, the need for high power artificial lift pumping system, and the complex crude treatment at topsides, among others. The field was discovered in 2001, followed by an appraisal program with a vertical well drilled yet in the same year to test the high porosity Eocenic unconsolidated sandstones and sample its heavy and viscous oil (14°API and 228 cP in reservoir conditions). In 2006, a horizontal well proposed to test the field development concept cast a shadow in the reliability of the project after facing several drilling, completion and production problems imposed by the high challenging environment. These included poor directional control leading to phase abandonment and well sidetracking, massive fluid loss, gravel packing failure, ESP operational issues, partially conclusive drill stem test (DST), and a severe damaged wellbore (skin = 40). After considering technology improvements and revisiting development concepts, an extensive preparation and a complete assessment of past operations were performed. During 2013 and 2014 the consortium led the drilling, completion and testing of the first two horizontal producers planned for the field development. Wells were drilled with good directional control and barely any fluid loss, reproducing with great fidelity the proposed trajectory. They were both completed with sand control screens and gravel packed throughout the 800 m near horizontal (88°) section in the reservoir. A slant section of 80 m was constructed just before reaching the reservoir for electrical submersible pump (ESP) installation. The DSTs were conducted with ESP both near the reservoir and near the seabed to test the performance of different artificial lift concepts. Results confirmed the high reservoir permeability and the great performance of the drilling and completion phases, delivering the first two producers of the field with no formation damage. Productivity indexes for both wells were in the high end of the expected performance. This paper presents a full review of the Atlanta Field, emphasizing its main challenges and how they were overcome by the successful construction and testing of the first two production wells, recovering the reliability of the project and encouraging the consortium to move on to the next phase. Also, the updated field development plan is described, highlighting the challenges to be faced during the next phase of the project.