World's First Gravel-Packed Inflow-Control Completion

Abstract

Summary The Etame oil field, offshore Gabon, West Africa, has been producing since September 2002. The Etame oil reservoir is an oval-shaped, low-relief structure with a moderate aquifer drive. To maximize ultimate field recovery, the ET-6H well was drilled with a horizontal lateral positioned to traverse the reservoir near the structural crest and to be within the Upper Gamba sandstone throughout its length. The Gamba sandstone averages 45 ft in thickness and overlies a significant angular unconformity. The subcropping Dentale-aged sandstones and interbedded shales below this unconformity have dips to 12°. The oil column of approximately 170 ft extends below this unconformity. Previous wells in the field were completed using openhole horizontal gravel packs (OHGPs) and have experienced excellent sand-control performance. However, OHGPs offer no protection against early water breakthrough. The Gamba sand averages 30% porosity with a permeability range of 1 to 3 darcies. The Dentale sands are much more variable, with porosities of 18 to 30% and a permeability range of 50 to 1,000 md. Thus, if a portion of the lateral is situated immediately above a high-permeability Dentale sand, the well will be at risk of early water breakthrough and subsequent reduced recovery if it is completed with a standard OHGP. The operator gravel packed the ET-6H well and used a system that provides a near-uniform inflow profile along the entire lateral length to protect against early water breakthrough. The gravel packing of inflow-control devices (ICDs) presented some unique challenges because of their differences from standard sandcontrol screens. This paper describes the implementation of the world's first gravel packed inflow-control completion, including: ICD selection process, gravel-pack design, data from the gravel-pack operation, and resulting well performance.