Best Practices for Frac Pack on High Permeability/Unconsolidated Reservoirs: Experience from Offshore Brazil Operations

摘要

The Campos basin is a sedimentary basin located in offshore Brazil,between the north coast of Rio de Janeiro State and the south coast of Espírito Santo State.Most of the reservoirs on the post-salt layers are high permeability sandstones(2,000 mD up to 6,000 mD),containing low API gravity oil.In addition to the high permeability,these sandstones are unconsolidated,which demands a sand control method to make oil and gas production feasible.In the original field development,conventional gravel packs were used as a sand control method,but post job analysis indicated high skins after the treatment,even using the best completion and placement techniques.This study offers an insight of the best practices and lessons learned from the design and pumping of more than 130 packs over more than two decades in offshore Brazil(water depths from 33 up to ~1800m).The main aspects discussed include frac pack design considerations,typical procedures,fracturing equipment overview,pressure management strategies and the need for a high quality fluid system and proppant.Frac pack completions were introduced in the end of the 90's and became a usual completion method for the Campos basin.Post job analysis indicates that this type of treatment provided better results than the convention gravel pack including lower skins after treatment.Due to the challenging reservoir characteristics,the strategy for frac pack design was to create a highly conductivity fracture,aiming to reduce the skin as much as possible,by using aggressive Tip Screen Out(TSO)designs.The TSO provides a short but wide and very conductive fracture,which is essential for high permeability wells.This technique bypasses the near wellbore damage caused by the previous drilling and completion practices such as drilling fluids,perforating debris and completion fluids invasion.This method can improve the effectiveness of the production,enhancing the oil recovery.