422 / 2024-04-01 12:23:55

Identifying the characteristics of fluid flow in tight sandstone reservoirs

Tight sandstone,Patchy saturation,Squirt flow,seismic wave,attenuation

The porous medium in unconventional oil and gas reservoirs, such as tight sandstone, usually consists of a complex structure with both pores and fractures. This complex network consists of both stiff and soft pores and fractures, leading to a heterogeneous development at  pore scale. Furthermore, the fluid distribution in the rock pores has a patchy saturation, where the diameters of the patches are usually larger than the dimensions of individual pores but less than the wavelength scale. This variations extends to the rock's mesoscale, affecting ithenteractions and wave-induced flow in tight sandstone at both the microscopic and mesoscopic scales. Recent studies challenged preconceived views about fluid flow characteristics by showing that micro-flow may occur within the acoustic and seismic frequency ranges, challenging the conventional approach. However, to really comprehend these occurrences, one must have a thorough understanding of the velocity and frequency characteristics at multiple frequencies, especially when it comes to velocity dispersion and attenuation analysis. Additionally, recent studies emphasize the non-uniform properties of subsurface porous media at all shapes and sizes, suggesting possible relationships between mesoscale wave-induced reactions and microscale wave-induced flow. Soft pores, for example, can dramatically change the wet modulus and frequency dependence of micro heterogeneous structures, which in turn affects the viscoelastic response of mesoscale media. In light of these discoveries, it is imperative to create a fluid flow mechanism that takes into consideration heterogeneities at the pore- and mesoscale levels and establishes velocity correlations throughout a range of frequency ranges in tight sandstone.