Efficiency of application of water-gas mixtures used to increase oil recovery and rearrange fluid flow

Abstract

Current development state of the several fields in Perm region shows low oil recovery coefficient and decrease in possible flooding that could maintain residual oil production at economically reliable level. Water-gas mixtures are used in order to increase development efficiency and oil recovery. Taking into account layered heterogeneous structure of reservoirs and its little thicknesses water-gas mixture could be effectively applied to create significant flow changing barriers. That could increase flooding and, as a result, oil recovery in different geological and technological conditions of siliciclastic and carbonate reservoirs development in Perm region. One of the gas methods of reservoir stimulation is injection of water-gas mixture that contain undispersed or dispersed gas phase. Application of such mixtures increases gas saturation in washed reservoir zones, reduces its phase permeability and rearrange the flow of displacing agents both in thickness and in size. Paper reveals application of water-gas mixture that contain undispersed or dispersed gas phase in order to finish oil displacement from siliciclastic and carbonate plug reservoir models made from two layers. Each of the two-layer models was made from two parallel plug models that model interlayer with low and high permeability. The results of carried study prove the efficiency of water-gas mixtures application for increase of oil recovery from carbonate and siliciclastic reservoirs as well as in flow rearrangement in layered heterogeneous reservoirs. The use of water-gas mixture that contain undispersed or dispersed gas phase leads to increase of displacement coefficient both in low-permeable and high-permeable models. Wherein, use of water-gas mixture with dispersed gas phase leads to higher displacement coefficient and more significant flow rearrangement. Comparison of the results of water-gas mixture application in siliciclastic and carbonate models showed that dispersed water-gas mixture is efficient while injection into both siliciclastic and carbonate reservoirs, application of undispersed water-gas mixture is more efficient in carbonate reservoir.

Keywords

• laboratory study
• core
• reservoir model
• permeability
• coefficient of oil displacement by water
• water-gas mixture
• layered heterogeneous re­servoir
• flow changing technology