Abstract: A method for producing oil and/or gas from an underground formation comprising locating a suitable formation with an oil column located above an aquifer; drilling at least one horizontal production well near a top of the oil column; performing primary production to produce a first quantity of fluids from the oil column; drilling at least one horizontal injection well at a location between the horizontal production well and a bottom of the oil column; injecting water mixed with a viscosifier into the horizontal injection well while producing a second quantity of fluids through the horizontal production well from the oil column.