Abstract: An apparatus for continuously generating and controlling the density of foam has a fluid in-flow manifold in communication with a source of liquid and comprising a pressure sensor. A plurality of branch lines are in fluid communication with the in-flow manifold a foam out-flow manifold. Each branch line has a flow control valve, a Venturi tube and in fluid communication with a throat of each Venturi tube an air induction control valve. The foam out-flow manifold has a pressure sensor. At least one in-flow control valve is disposed between the source and the in-flow manifold and at least one out-flow control valve is in communication with the out-flow manifold. The branch valves, air valves, the in-flow control valve and the out-flow control valve are operable to provide a chosen flow rate of the liquid and a selected foam product flow rate at a selected density of the foam product.

Abstract: A method for pumping a liquid-gas mixture into a subsurface well includes introducing gas into a liquid at a first pressure to generate a mixture. The mixture is pumped through a first positive displacement pump to a second pressure greater than the first pressure. The mixture at the second pressure is pumped through at least a second positive displacement pump to a third pressure greater than the second pressure. The mixture is moved into the subsurface well at at least the third pressure.

Abstract: An apparatus for continuously generating and controlling the density of foam has a fluid in-flow manifold in communication with a source of liquid and comprising a pressure sensor. A plurality of branch lines are in fluid communication with the in-flow manifold a foam out-flow manifold. Each branch line has a flow control valve, a Venturi tube and in fluid communication with a throat of each Venturi tube an air induction control valve. The foam out-flow manifold has a pressure sensor. At least one in-flow control valve is disposed between the source and the in-flow manifold and at least one out-flow control valve is in communication with the out-flow manifold. The branch valves, air valves, the in-flow control valve and the out-flow control valve are operable to provide a chosen flow rate of the liquid and a selected foam product flow rate at a selected density of the foam product.

Abstract: A method for pumping a liquid-gas mixture into a subsurface well includes introducing gas into a liquid at a first pressure to generate a mixture. The mixture is pumped through a first positive displacement pump to a second pressure greater than the first pressure. The mixture at the second pressure is pumped through at least a second positive displacement pump to a third pressure greater than the second pressure. The mixture is moved into the subsurface well at at least the third pressure.