Immiscible water alternating gas (IWAG) injection has effectively managed produced gas at the Kuparuk River Field: increasing field oil rate and recovery. Although IWAG economics are very favorable, this pilot study was undertaken to ascertain whether separate water and gas injection lines to the drill sites and on-pad distribution systems can be eliminated by simultaneously injecting water and gas in waterflood lines.
A significant problem in simultaneous water and gas injection is the phase separation which occurs at branches in the injection pipe network. The higher density phase, because of its greater momentum, will tend to flow in the straight or least deviated pipe branch, while the lower density phase will tend to flow into the most deviated branch of pipe. Studies conducted at ARCO’s Exploration and Production Technology Research Center in Plano, Texas; indicated that static mixers positioned at the pipe branches could achieve equal distribution of the phases to both runs of the pipe branch.
In the pilot study gas was injected into an 8″ waterflood line which supplied two drill sites. A static mixer was placed at the junction for the two drill sites. Static mixers were also placed in the 4″ injection manifold of one of the drill sites, the other drill site had no mixers in the injection manifold. Gas was distributed to both drill sites. At the drill site with static mixers in the injection manifold, gas was distributed to the wells on the injection manifold: while at the drill site without static mixers, phase separation occurred and only one well on the injection manifold received gas.