Experimental Study of the Impact of Methane Addition on Heavy Oil Recovery through Steamflooding

Summary In this study, we undertook a comprehensive examination to assess the impact of methane (CH4) addition on heavy oil recovery through steamflooding. Our investigations involved conducting steam and steam-CH4 flooding experiments within sandpacks under conditions mimicking those found in sandstone reservoirs. Furthermore, we conducted specific experiments to elucidate the main recovery mechanisms, including oil recovery by thermal expansion from rock-oil systems, oil swelling, and oil viscosity reduction. Due to swelling being contingent upon both oil thermal expansion and the concentration of dissolved gas, we utilized recombined oil, brine, and outcrop sand in our recovery and swelling experiments to accurately evaluate the effects attributable to CH4. Additionally, we devised a procedure to determine the oil swelling factor, using data from CH4 diffusion tests and thermodynamic software. In the realm of steam-CH4 flooding experiments, our findings revealed a noteworthy 13% enhancement in oil recovery compared with steamflooding, coupled with an accelerated oil production rate. Our results show that despite factors such as dissolved gas and thermal expansion of oil and rock, the oil experienced a swelling of 3.46%. Moreover, at the initial stages, the introduction of CH4 facilitated a temperature elevation of the sandpack by 40°C beyond that achieved with steam alone, owing to the heat propagated by CH4 ahead of the steam front. Furthermore, the incorporation of CH4 into the steam process resulted in a reduced steam-to-oil ratio, declining from 12.5 for steam to 7.7 for steam-CH4. Based on our findings, incorporating CH4 into the steamflooding process has the potential to significantly improve both its efficiency and overall effectiveness.