Figure 12. Carbon dioxide, hydrogen sulfide, and organic acids evolved during hydrocarbon generation mix with connate waters in the burial environment to produce acids. These acidic fluids can migrate both vertically and laterally for great distances, even affecting carbonate rocks that are not deeply buried (5). Acidic fluids can migrate along faults (1), along bedding planes or porous strata within beds (2), along formational boundaries (3), or upward along fractures through otherwise non-permeable beds ("cross-formational flow" (4).