Gas lift, a broadly applied method for producing oil, consists of gas injection into production wells to reduce the liquid density in the wells and increase the liquid inflow. Gas lift technology requires large gas volumes to be injected. If the reservoir pressure is depleted, the effectiveness of gas lift is dramatically reduced. To increase effectiveness and to extend gas lift applications to producing oil from depleted reservoirs, a foamed gas lift method has been investigated in laboratory and oilfield experiments. The method consists of foaming agent injection into a gas-liquid flow.

A laboratory set-up based on scaling parameters was used to study the productivity of the gas lift well exploiting the drainage area of the well. The laboratory experiments were performed over a wide range of the scaling parameter, describing the reservoir pressure depletion, with and without foaming agent. The results show that foamed gas lift would be efficient, especially if the gas lift well cannot produce without the addition of foaming agent. Analysis of the gas-liquid flow structure inside a vertical tube displayed the conditions of effective application of the foaming agent to improve gas lift technology. Oilfield experiments analyzed with probability theory corroborated that foamed gas lift is a very effective technological method if the reservoir is depleted

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