Method and device for determining the threshold of heavy fraction deposit contained in a liquid hydrocarbon fluid

A method for determining the deposition threshold of heavy fractions contained in the dissolved and/or stable colloidal state in a liquid hydrocarbon-containing fluid, comprising the following steps:

• (a) driving a sample of the fluid, maintained at a constant pressure and temperature and such that the heavy fractions present in the fluid sample are in the dissolved and/or stable colloidal state, to an inlet of a capillary line to generate a pressure drop between an inlet pressure and an outlet pressure respectively between an inlet and an outlet of the capillary line at least equal to a difference between the pressure of the fluid sample and a bubble-point pressure of the fluid sample;
• (b) establishing an initial outlet pressure equal to the inlet pressure;
• (c) generating, by operating at a constant temperature equal to the temperature of the fluid sample, a flow of the liquid hydrocarbon-containing fluid, at an increasing flow rate, through the capillary line, until the outlet pressure has dropped from the initial pressure to a predetermined pressure above the bubble-point pressure of the fluid sample;
• (d) measuring a pressure difference ΔP between the inlet pressure and the outlet pressure (Ps) and/or the outlet pressure (Ps) as well as a flow rate (D) of the liquid hydrocarbon-containing fluid flowing through the capillary line;
• (e) detecting a change in the variation rate of a first of the two quantities pressure difference (ΔP) and flow rate (D) as a function of time, or as a function of the second of the two quantities, or of a quantity representative of the second of the two quantities;
• and
• (f) defining as a deposition pressure of the heavy fractions, at the constant temperature, for the liquid hydrocarbon-containing fluid, the fluid pressure at the outlet of the capillary line which corresponds to a start of the change in variation rate, this pressure characterizing the deposition threshold of the heavy fractions for the fluid sample.