- Under review
Abstract — Rock pore structure and capillary number play significant roles in gas-water flow in limestone, which is of key importance for natural gas production and gas storage. However, direct evidence of how limestone type and pore space morphology (vugs versus fractures versus homogeneous pore matrix) and capillary number control gas-water two-phase flow in 3D is still limited. Here, we thus studied the dynamic movement of gas and water in various limestones via in-situ X-ray microtomography combined with numerical flow simulations. We demonstrated that in these water wet cores, gas first entered large pores/vugs, and, at higher gas flow rates also entered micro fractures. In contrast, water entered smaller pores first (due to the rock’s wettability). Moreover, the volume surface area relationship of trapped gas fitted a power law relationship (independent of limestone type) with an exponent (p ≈ 0.77). Based on the simulation results, less residual gas distributed at dead end corners at low capillary number, and part of the residual gas can be displaced by increasing water flow rate. This work thus provides fundamental data and improves fundamental understanding of gas-water flow in limestones, and therefore helps in the further advancements of improved hydrocarbon recovery and gas storage in limestone reservoirs.