This master thesis treats the problematic of chalk particles in the production stream coming from the Tyra Field in the North Sea. The reservoir formation consists of chalk. A litterature survey is accomplished in order to explain the mechanism behind some massive chalk influxes observed, and a possible explanation is found to be pressure variations in the switch form injection to production of gas.
Unit operations used for removal of small chalk particles from the stream of produced water is examined. A proposal for use of centrifuges for water treatment is made, since this technique, dependent on the volume of solids, can remove particles down to 0,1µm whereas normal hydro cyclones have a limit of 10µm.
The ζ-potential of the chalk particles is determined, and an interaction of the ionic species on the ζ-potential is found. A shift in operational sign is seen at low and high values of pH respectively. A series of experiments and analyses gives a possible explanation of this phenomena by watching the equilibrium and formation of HCO3- at low pH and CaOH+ and MgOH+ at high pH. These found ionic species are proposed as potential determining ions for chalk.
The possible formation of emulsions of oil/water/chalk solutions and the possible stabilizing effect of these by small chalk particles is examined. The results did not indicate clear evidence that chalk particles stabilize an emulsion of oil/water.
The ability of chalk to drag oil from the oil phase to the water phase is observed. By examining samples of chalk taken from the water phase under the microscope, particles are found which are encircled in oil.