BJET and KOHRYE are Det Norske Veritas (DNV) tools for computing chemical/hydrocarbon concentrations in the water masses. The two models may be run together or separately.

The BJET model is developed at the Norwegian Institute of Technology and has been improved by DNV (ref. /1/), and simulates regular sub sea releases close to the discharge orifice where the flow has a character of a jet/plume. The KOHRYE model, originally developed by Koh and Fan (ref. /6/), has been improved by DNV and simulates far-field advection and diffusion of both surface and sub sea releases (ref. /2/). These models have been used on several environmental projects, nationally and internationally.

A KOHRYE far-field simulation result (hydrocarbon concentration field) is presented below, based on BJET simulation of a sub sea release of produced water (near zone).

The validation study shows a general deviation between BJET predications and measured dilution within +/- 25 % (ref. /3/, /4/ and /5/). The predicted equilibrium depth is also in good agreement to the observations.

The BJET sensitivity study shows that the ambient velocity, the initial density of the release and the ambient density profile was the dominating variable. More details about the sensitivity and limitations of the BJET model are described ref. /5/.

The agreement between the analytical and numerical KOHRYE solutions has been found to be excellent (ref. /2/).

Simulations can only be made for stationery scenarios with release of conservative effluents.

References:

1. Sørgård E. 1992 A; BJET, the sub-sea buoyant jet model, Det Norske Veritas 1992, Report no. 92-2055
   
2. Sørgård E. 1992 B; KOHRYE, the far-field advection/diffusion model, Det Norske Veritas 1992, Report no. 92-2056
   
3. Hagen D.E. 1994; BJET, Sensitive Analyses and Validation, Det Norske Veritas 1994, Report no. 94-3492 (in Norwegian)
   
4. Smith, J.P. et. al 1993; Field Observations of Produced Water Dilution: Comparison With Dispersion Model Predictions, Report prepared for the Offshore Operators Committee, 1993
   
5. Skåtun, H.; BJET, A buoyant model for sub sea releases, 1995 International Seminar on Produced Water, Trondheim 1995
   
6. Koh, R.C.Y. Fan, L.; Mathematical models for the prediction of temperature distributions resulting from the discharge of heated water into large bodies of water, Water Quality Office, Environmental Protection Agency, 1970