Viscosity, phase separation and pour point are evaluated mainly for determination of the handling properties of the material. Chemicals, which are not single phase at a wide temperature range, or freeze in winter, and/or have excessive evaporation of solvents in hot summers are usually eliminated or reformulated.
Density is determined to check if proper mixing of the chemical will be realized in the field.
Solubility/dispersibility of the formulations is tested for compatibility with the produced fluid. The solubility/dispersibility of the oil field chemicals is based on visual observation of the clarity or turbidity of untreated field samples of brine or hydrocarbon phase when a level of the oilfield chemical is added at the temperature of the sampling point. The results are expressed as degree of solubility, visible chemical phase, dispersibility, turbidity of both phases. Scale inhibitors usually need to be soluble in the brine. Demulsifiers need to be compatible with the type of emulsion found in the field. Corrosion inhibitors need to be at least dispersible in the brine.
Emulsion forming, sludge/precipitate forming and foaming tendencies are performed to check for any possible reaction of the formulation with the other chemicals injected in the field and with the produced fluids. Typical emulsion forming tendency tests are performed in untreated field samples at the temperature of interest. The method consists of adding a high concentration of oilfield chemical to the proper ratio (brine/hydrocarbon) of produced fluid. The container is then shaken and the presence of emulsion, solid or sludge is noted. If solids or sludge are formed at high concentration, incompatibility of the oilfield chemical with the produced fluids is possible.
Foaming methods usually consists of introducing untreated sample of brine and/or hydrocarbon in a graduated cylinder with inhibitor concentration varying from 50 to 2000 ppm at the temperature of interest. The cylinders are then sparged for 10 minutes with a gas mixture consisting of CO2 and/or H2S typical of the field conditions with a dispersion tube. The evaluation consists of measuring the height of the foam column formed as a function of time.
More specialized tests are also performed on corrosion inhibitors. The fall rate of high density inhibitors and the effect of temperature on their release time in oil-brine mixtures are determined when the chemical will be batch injected. The stability of the formulation at high temperature is also important when the chemical is used for inhibition of downhole equipment.