AIba Field Cased Hole Horizontal Gravel pack -A Team Afw?oachTo Design
Authors: Alexander Karen , Winton Suzanne , Price Colin 
Published: October 2008

A 700? cased hole horizontal well was gravel packed and completed in the Alba Field, Central North Sea. The completion incorporated a number of new technologies adopted for a horizontal cased hole completion including both equipment and fluids. The zone was completed in 2 stages using a horizontal stack pack approach. Perforation packing was optimized by performing a staged acid prepack with the guns in the hole utilizing a 10w density synthatic gravel substitute in a shear thinning carrier fluid. This was a world first achievement at a cased hole gravel pack using tha stack pack approach in a horizontal well. A solids free fluid loss control material was evaluated and chosen for the high permeability Alba sands (3 Darcy), Extensive lab testing was performed to ensure minimal damage from various fluids. A 30? ph ysical model was used to optimize annular pack efficiency. A gravel placement computer simulation was used to design pump rate, sand concentration and gel loading in order to optimize annular and perforation pack efficiency.

INTRODUCTION

The objective of the paper is to highlight the advantages of working as a team to resolve a problematic completion, This allowed utilization of the tools available in the industry for optimizing gravel packs to avoid damage. The approach adopted consisted of setting up a high efficiency team with appropriate technical knowledge and experience. The team?s first task was to identify and then systematically address the concerns. The outcome of this exercise would be a procedural flowchart which fully addressed concerns via a solutions based approach.

FIELD DESCRIPTION

The Alba Field is located in Block 16/26 of the UK Continental Shelf, lying about 130 miles north-east of Aberdeen in 138 metres of water, The reservoir is a long, narrow Eocene aged sandstone deposit located at a depth of approximately 6,000 feet TVD. The field was discovered in 1984, and field approval (Annex B) was granted in May 1991. First production was in January 1994.

The main challenges faced in the development of the Alba Field from a reservoir management perspective are summarised below:The Alba crude is heavier and more viscous (20,6"API) than the North Sea standard (46"API) The reservoir is almost totally underlain by an inactive aquifer which is forecast to cone severely, resulting in very high produced water rates in comparison to the crude oil production rates. Water cut is expected to reach 70% within 7 years, rising eventually to 95% by 20100.The reservoir is unconsolidated with a permeability in the range of 3 Darcy. Safe sanding threshold pressures are 200 psi for an oil bearing sand and O psi for a water bearing sand hence sand control techniques were required from initial production. Initial reservoir pressure is 2850 psi and artificial lift would be required as water cuts approach 55%.70% within 7 years, rising eventually to 95% by 20100.The reservoir is unconsolidated with a permeability in the range of 3 Darcy. Safesanding threshold pressures are 200 psi for an oil bearing sand.