GOR-Control Foams: Demonstration of Oil-Based Foam Process Efficiency in a Physical Flow Model

Abstract

Abstract Production at high gas/oil ratio (GOR) is a problem in many reservoirs and occurs because of the high mobility of gas in the formation. Horizontal wells can be a solution to produce thin oil rims, but depending on the reservoir, these may also give unwanted gas production. Foam has been developed into an attractive GOR-control agent. Combining the use of foam with horizontal wells will possibly reduce the production of unwanted gas to an acceptable level. Placement of foam barriers at the gas-oil contact plays a crucial role for a successful treatment. One option is the injection of an aqueous surfactant slug followed by nitrogen or methane gas injection. Since an aqueous solution has a tendency to segregate downwards, foam can only be created by following the surfactant with gas injection. A better injection scheme would be to inject a surfactant dissolved in a non-aqueous solvent having a lower density than the oil in place. Such a slug will segregate upwards to the gas-oil contact and form a layer. When the well is on production and gas tries to migrate through the surfactant layer a gas-blocking foam barrier will be formed. As part of ongoing research towards qualifying the use of gas-blocking foam to control the GOR in producing wells, a new design of laboratory model of an idealised heterogeneous oil/gas reservoir penetrated by a horizontal well was developed. The physical flow model was used to study two phase production of oil and gas with and without the presence of a foam that has previously been shown to block gas efficiently in one-dimensional lab experiments. The results of these 2D model experiments are described in the paper and suggest that foam barriers are well suited for protecting horizontal wells in heterogeneous reservoirs. The results include injection of foaming-agent solution, showing gravity-controlled placement, generation of gas-blocking foam by production start-up, and successful GOR reduction by the foam barrier, all proceeding as expected from previous work.