Please, can anybody direct me to some materials / experiences for the case when during the well testing quantity of some 4 000 m3 of water/day has to be cooled from cca 85 C to 20 C before it is discarded to surface natural waters
Thank you
If the water is clean (ready to be discarded) and the "natural waters" is colder than 20 deg C - then why not just "premix" it with these "natural waters". Lay out a hose and pump up the water and mix it so that the resulting temperature is 20 deg c?
That is a bunch of water and an awful lot of heat rejection.
The heat works out to 2.6E8 kJ (2464 MMBTU/day or the equivalent heat of 2.5 MMCF/d of methane). I don't know any "quick and dirty" way to get rid of that much heat. If you have a bunch of surface water (i.e. offshore) then you could design a specific water-water heat exchanger to pump a few million m^3/day through one side to result in your produced water being at the right temp without the heat exchanger exhaust being too hot.
I recently designed an evaporation pond for 1/5 that much water and the pond surface was 75m X 75m. I don't think that you're going to be successful rejecting the heat to atmosphere.
If this is an ongoing produced-water disposal problem, suggest you look at a binary-cycle power generation plant such as ORMAT (Israeli I think). These systems use Propane or Ammonia as the power fluid and don't recall the OA efficiency but would think that you could generate quite a few MWe. $100/BBL for your oil and $10/BBL for your water?
Aside from capital cost, a problem you may run into is Calcium Carnonate/Barium Sulphate etc precipitating out in the heat exchangers as the temperature drops.