A Challenging Workover in an Offshore Fixed Platform - Accessing Bypassed Hydrocarbons

摘要

This paper presents the planning, execution, and lessons learned of a challenging workover focused on accessing bypassed hydrocarbons for production increase. The workover goal was to add two-bypassed zones, a high quality upper carbonate zone and a thin bed of sandstone, both above the production casing shoe, to the openhole carbonate production of a horizontal well in a fixed offshore platform. Polvo is a brown or mature field in shallow waters of Campos Basin, Brazil. Among the typical problems of mature fields, Polvo shows only pressure drop, declining oil rate, and high water influx, with 80% average water cut. To extend the economic life of Polvo, a huge challenge in the current downturn, its independent operator is rejuvenating existing producing wells, optimizing flow, and identifying, quantifying and accessing bypassed hydrocarbons. The original well was completed in a lower carbonate zone in a 604 m openhole lateral section with sand control screens. After reviewing reservoir and well data, the operator team found the two mentioned bypassed zones. In order to access these zones, it was necessary to perforate them, to control sand production in the sandstone, and to deploy an intermediate completion. Because of internal diameter restriction in the lower completion, hydrajetting replaced casing gun operations in both zones. Sand control in the high angle sandstone interval was a challenge. A specific fracturing/gravel operation followed, successfully, a failed sandstone consolidation trial. Among the main challenges this workover faced budget and time limitations, once the rig operated on a temporary contract, and material, equipment, and footprint restrictions, not mentioning lack of relevant information about the bypassed sandstone zone.