Gas-Oil Interaction and Gravity Impact on High-Permeability WAG Experiments
Year: 2026
Type: article
Abstract: This study investigates the impact of gas-oil interactions and gravity on miscible water-alternating-gas (WAG) coreflood experiments representative of a high-pressure, high-permeability offshore sandstone reservoir. A key objective is to quantify how thermodynamic exchanges (swelling and stripping) and flow segregation influence recovery efficiency under different injection strategies. A comprehensive experimental program was conducted, including four WAG corefloods performed at reservoir conditions using live oil and representative reservoir rock, with both long and short slug sequences (G/W/G/W and W/G/W/G). A dedicated vertical experiment was designed to isolate gravity effects. Additional two-phase experiments were performed for comparison. Advanced experimental monitoring combined material balance, compositional analysis, and real-time two-dimensional (2D) X-ray imaging (CXBox) to quantify fluid distributions and thermodynamic exchanges. History matching of one-dimensional (1D) and 2D numerical models was performed to derive two-phase relative permeabilities and three-phase flow parameters specific to WAG cycling. The experiments demonstrate that gas-oil interactions strongly control recovery efficiency under miscible conditions, with significant contributions from both swelling and stripping mechanisms. Alternating water and gas injections improve gas distribution, reduce override, and enhance sweep efficiency compared to continuous gas injections. Gravity effects were found to significantly alter flow behavior: horizontal experiments exhibited gas override and limited vertical sweep, whereas vertical configurations reduced the contact area and limited thermodynamic exchanges. Short WAG slugs showed the fastest recovery and the most efficient three-phase displacement, confirming the synergistic effect of alternating phases. Overall, three-phase WAG processes enable faster attainment of high recovery factors compared to two-phase or single-phase injection schemes. This work provides a unique, fully integrated data set combining compositional measurements, saturation monitoring, and direct visualization of three-phase flow under reservoir conditions. The study highlights the critical role of gas-oil thermodynamic interactions in WAG efficiency and demonstrates how gravity and slug design influence the balance between flow segregation and mixing, offering valuable insights for the calibration of three-phase reservoir simulation models.
Language: English
Subfield: Ocean Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W6912277286
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