Visualizing and Quantifying Fluid Flow in Multi-Coal Reservoirs Using Three-Dimensional Monitoring Data

To investigate the three-dimensional spatial distribution characteristics of fluids during the combined production of coalbed methane from multi-coal reservoirs (MCR), a physical simulation test platform was established, and a quantitative characterization parameter calculation principle for fluid migration was developed. The influence of fluid pressure difference and in situ stress difference on the three-dimensional spatial distribution of fluids and their quantitative characterization parameters was analyzed. The results indicate that the dynamic pressure equilibrium between the coal reservoir and the wellbore forces fluids from high-pressure reservoirs to intrude into low-pressure reservoirs, altering the flow state of fluids in the latter. Consequently, the relative flow velocity in the low-pressure reservoir becomes negative, with the relative deflection angle approaching 180°, while the relative flow velocity in the high-pressure reservoir remains positive. An increase in the relative flow rate of 0.08 and 0.007 corresponds to a 1 MPa increase in fluid pressure difference and geostress difference, respectively. During the co-production of coalbed methane from MCR, the existing pressure difference and in situ stress difference between reservoirs modify the fluid migration patterns, leading to fluid interaction and interference effects. This results in centrifugal flow patterns in low-pressure reservoirs and centripetal flow patterns in high-pressure reservoirs. Compared to in situ stress difference, the fluid pressure difference exerts a more significant influence on the fluid migration patterns.