Water in Petroleum Systems
Water in Petroleum Systems

WiPS.consulting GmbH

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Re-calculated compositional data from available formation water information offer multiple applications. They may be applied to correctly identify in-reservoir hydrogeochemical conditions prior to technical measures such as injection of seawater, low salinity water or “designer water”. The WiPS hydrogeochemical modeling approach can furthermore help to avoid undesirable effects of formation water-rock-gas interactions which are caused by water injection or chemicals.


In order to correctly recalculate the hydrogeochemical sitution in the deep aquifer, batch and one-dimensional reactive transport modeling is performed under consideration of the dependance of the equilibrium distribution of species  on temperature, pressure and ionic strength.

 

Suitable tools for hydrogeochemical recalculations were developed by the U.S. Geological Survey:

  • PHREEQC (Version 3) computer code (Parkhurst and Appelo, 2013), together with its
  • phreeqc and wateq4f databases (and the extended thermodynamical PITZER (gebo) data base for very high ionic strength conditions above with I > 1.5 mol/kgw in sodium and chloride dominated solutions; Bozau, 2013).

 

The application of both tools allows to correctly model hydrogeochemical processes under high temperature, pressure and ionic strength conditions (Bozau and van Berk, 2013). Such modeling approaches can simulate the sampling-induced effects which are due to  

  • total pressure decrease: triggers outgassing of CH4 and CO2 and scaling,
  • temperature decrease: triggers scaling, and
  • metal corrosion of casing and/or production tubing[1]: triggers scaling.

By using such a re-constructed chemical in-situ composition of formation water, subsequent hydrogeochemical modeling can be applied:

  • for the identification and quantification of mineral dissolution and/or precipitation induced by oil degradation,
  • for the quantification of the CO2 fate and partial pressure resulting from oil degradation, and
  • for the identification and quantification of in-reservoir scaling and wellbore scaling both resulting from water injection.

 


[1] According to Hitchon (2000), the source for elevated levels of iron dissolved in produced waters from deep wells is metal corrosion. Hitchon, B., 2000, “Rust” contamination of formation water from producing wells, Applied Geochemistry, 15, 1527-1533.