Application of ultrasonic irradiation for well deliverability improvement in gas-condensate reservoirs

In gas condensate reservoirs the process of condensation around the wellbore, when the pressure falls below the dewpoint, creates a condensate bank that can drastically reduce well productivity, requiring additional expensive wells to maintain the production level. Conventional remedial methods relying on removing the condensate bank are not generally long lasting, requiring repeated treatment.In this paper we present results of a study on the feasibility of using ultrasonic energy to alleviate the above problem by reducing the flow resistance in this region. Ultrasonic excitation of gas condensate systems was visually examined using high-pressure glass capillary tubes and micromodels with realistic pore patterns, simulating pores of a reservoir rock.Capillary tube experiments demonstrated that ultrasound radiation caused the gas-condensate interface to oscillate. In addition to destabilising the static equilibrium position of the interface, this oscillation also causes local mixing effects at the interface, lowering the effective liquid/gas interfacial tension. Results of our flow experiments in high-pressure glass micromodels showed that a significant amount of condensate was mobilised and recovered as a result of the application of ultrasound energy. We also show theoretically, that the radiation pressure caused by ultrasound waves exerts a net force on a fluid/fluid interface placed along the line of propagation of the wave. This force is a function of the phase difference between the applied acoustic field and the oscillation of the interface with the force being maximum at the resonance frequency.