This paper describes a two-step frac/gravel pack completion procedure conducted from a jack-up rig offshore Gabon in 1993 and 1994. After an in-depth, sand production study, seven wells were completed using hydraulic fracturing and cased-hole gravel packs.
Because the Anguille formation spreads over a large gross interval, production screens of 50 to 100 m in length were used. Single-stage internal gravel packs (IGPs) on such large intervals were considered impossible to achieve with reasonable skin values.
The frac-pack technique was an attractive way to achieve good proppant placement, considering that the formation being fractured would have a more homogeneous conductivity across the whole zone and a uniform proppant placement would be achieved in the perforations as well as in the annulus.
High-efficiency frac gel using cross-linked HPG and a low damage one using HEC were compared to determine the best fluid to be used for these completions. Bottom hole pressures during treatment operations, as well as post-treatment pressure build-ups from each well, were analyzed in order to make general recommendations on this hydraulic fracture design.