Impact of Fluid‐Induced Pore Geometry Alteration on Acoustic Velocity in Carbonate Rocks

Abstract We performed laboratory experiments to study the effects of fluid‐induced precipitation and dissolution on pore space geometry and corresponding acoustic velocity in carbonate rocks. This approach separates the impact of pore structure changes from other factors like compaction and tracks only variations in acoustic velocity alongside changes in porosity resulting from calcium carbonate cementation and dissolution. In the precipitation experiments, the degree of velocity variation is strongly influenced by the specific location of cementation. Grain‐contact cementation strengthens the rock framework, which results in a marked increase in acoustic velocity, while the growth of intrapore aragonite crystals usually produce more intricate, softer frameworks that have a minimal effect on velocity yet generally cause a slight reduction. Dissolution predominantly eliminates non‐load‐bearing small particles, which leads to increased porosity yet results in only a marginal decrease in acoustic velocity. The dissolution creates bigger void spaces in the rock without increasing its structural complexity while maintaining its inherent strength. Using the parameters of internal pore geometry, including dominant pore size and perimeter‐over‐area ratio, we demonstrate that pore geometry has a greater influence on elastic properties and acoustic velocity than porosity by itself. These results question standard porosity‐velocity models while demonstrating the need for quantitative pore geometry parameters in rock physics models that analyze seismic reflection data. Without integrating pore geometry parameters, seismic data analysis risks underestimating porosity in dissolution areas or incorrectly classifying grain‐contact cementation as lithological changes.