In
geology and
sedimentology
Sedimentology encompasses the study of modern sediments such as sand, silt, and clay, and the processes that result in their formation (erosion and weathering), transport, deposition and diagenesis. Sedimentologists apply their understanding of mo ...
, connate fluids are liquids that were trapped in the pores of
sedimentary rocks as they were deposited. These liquids are largely composed of
water, but also contain many
mineral components as
ions in
solution.
As rocks are buried, they undergo
lithification and the connate fluids are usually expelled. If the escape route for these fluids is blocked, the pore fluid
pressure can build up, leading to
overpressure
Overpressure (or blast overpressure) is the pressure caused by a shock wave over and above normal atmospheric pressure. The shock wave may be caused by sonic boom or by explosion, and the resulting overpressure receives particular attention when m ...
.
Significance
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. Minute bubbles of fluid are often trapped within the
crystals of the cementing material. These
fluid inclusions provide direct information about the composition of the fluid and the pressure-temperature conditions that existed during diagenesis of the sediments.
Some analyses of connate water samples from Louisiana (USA) compared to seawater
Similar, but different in origin, is the concept of
fossil water, which is used to describe very old
groundwater found in deep
aquifers or bedrock. 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.
See also
*
Petroleum geology
Petroleum geology is the study of origin, occurrence, movement, accumulation, and exploration of hydrocarbon fuels. It refers to the specific set of geological disciplines that are applied to the search for hydrocarbons (oil exploration).
Sedime ...
References
{{Reflist
Connate waterat Schlumberger Oilfield Glossary
Petroleum
Sedimentology
Soil mechanics