In geology and sedimentology, connate fluids are liquids that were trapped in the pores of sedimentary rocks as they were deposited.
An understanding of the geochemistry of connate fluids is important if the diagenesis of the rock is to be quantified.
The solutes in the connate fluids often precipitate and reduce the porosity and permeability of the host rock, which can have important implications for its hydrocarbon prospectivity.
The chemical components of the connate fluid can also yield information on the provenance of aquifers and of the thermal history of the host rock.
Typically it was recharged during a different climatic period (e.g., the last ice age) so is also very old, but possibly not of the same genesis as the rock.