Enhanced Oil Recovery Based on “Advanced Water” Flooding

Advanced water flooding is a process in which the ionic strength as well as the ionic composition of the injected water is tuned to substantially improve normal oil recovery. This method has been shown in lab coreflooding experiments and field trials to recover additional oil compared to standard waterflooding. The process modifies wettability in carbonate reservoirs releasing oil otherwise trapped in the pores. The potential of advanced waterflooding has been proved at field scale in the Ekofisk oil field that is producing from Tor and Ekofisk chalk reservoirs located in Norwegian North Sea. At Ekofisk, recovery increased from 19% to 51% by changing injected water chemistry from formation water to seawater. Selectively modifying the chemistry of seawater can further improve recovery at nominal cost, particularly in reservoirs that already show good waterflood response.

Water flooding anvendes i oliefelter, hvor det oprindelige olietryk er aftaget efter produktion af den let tilgængelige olie i oliereservoiret. Der anvendes typisk havvand, som sendes ned i en injektionsbrønd for at øge trykket og dermed at kunne fortsætte olieproduktionen. Der arbejdes på at variere sammensætningen af den injekserede havvand til de i Nordsøen eksisterende kalkfelter for at kunne forøge olieudbyttet ved water flooding. Undersøgelserne foregår i laboratoriet involverende avanceret model udstyr til water flooding og andre metoder til at opnå en fuldstændig forståelse for vekselvirkningen mellem olie, kalk, formationsvand (brine) og det anvendte vand til water flooding.