Increase liquid oil production by huff-n-puff of produced gas in shale gas condensate reservoirs

Abstract

Huge shale resources available and low gas price turn the oil operators’ activities to producing more liquid oil. The earlier studies from our research group and others show that huff-n-puff has the highest potential to improve oil recovery (IOR) in shale oil reservoirs, compared with common IOR methods of gas flooding and waterflooding. This paper is to extend the research to shale gas condensate reservoirs to evaluate the IOR potential. The simulation analysis approach is used.The simulation results and discussions in this paper show that huff-n-puff injection of produced gases can produce more liquid oil in gas condensate reservoirs than gas flooding or primary depletion. This result is verified by all the simulated cases with different reservoir and fluid properties and operation conditions. The advantages of huff-n-puff over gas flooding are the early response to gas injection, high drawdown pressure, oil saturation decrease near the wellbore by evaporation, and overcoming the pressure transport problem owing to ultra-low permeability. The advantages become more important when the initial reservoir pressure is close to the dew point pressure, or the bottom-hole flowing pressure is low. The effects of injected gas composition, cycle time and soak time during the huff-n-puff process are investigated. A simple economic analysis is also conducted.