Method of determining the stability reserve and solubility parameters of a process stream containing asphaltenes by joint use of turbidimetric method and refractive index
A method is provided for determining the solubility parameters for a process stream via the joint use of turbidimetric detection of asphaltenes flocculation, which is used to determine and detect the onset flocculation of asphaltenes of the process stream, and a refractive index to determine the process stream solubility parameters such as the solubility blending number and insolubility number.
1. A method of controlling a crude oil upstream process having a process stream containing asphaltenes, the method comprising:
deploying a refractive index probe at a location suitable for making a crude oil stability determination;
determining the solubility parameters and stability reserve of the crude oil; and
controlling the crude oil upstream process by maintaining the process or implementing a change to the process based upon the determination of the solubility parameters and stability reserve, the step of determining comprising:
(a) determining the solubility parameters by measuring a refractive index of the process stream (RI) and the refractive index at a flocculation onset of the asphaltenes (RIo), wherein the flocculation onset is determined via turbidimetric titration, and wherein the measuring comprises:
(i) utilizing the refractive index parameters of the process stream (RI) as a direct measurement of a solubility blending number (SBo); and
(ii) utilizing the refractive index parameters at the flocculation onset of the asphaltenes (RIo) as a direct measurement of an insolubility number (IN);
(b) determining the stability reserve by calculating the stability reserve from the solubility blending number (SBo) and the insolubility number (IN), wherein the process stream comprises a live crude oil;
(c) recovering precipitated asphaltenes at the flocculation onset, redispersing the precipitated asphaltenes in a solvent to form an asphaltenic solution, measuring the refractive index parameters of the asphaltenic solution (RIa), and converting the refractive index parameters (RIa) into a solubility blending number (SBa) of the precipitated asphaltenes;
(d) making a measurement of crude oil stability, wherein the difference in the solubility blending number of the oil and the IN measured from RIo at the asphaltenes flocculation onset (SB o -IN) is indicative of the stabilizing/solvating role of one or more resins in the fluid on the asphaltenes; and
(e) making a measurement of the stabilizing/solvating role of the resins in the fluid on the asphaltenes, wherein the difference in the solubility blending number of the oil and the solubility parameter of the process stream with precipitant at the flocculation onset (SB a -IN) is indicative of the stabilizing effect of the resins.
2. The method of claim 1 , wherein the precipitated asphaltenes are recovered via one or more of filtration or centrifugation.
3. The method of claim 2 , wherein the recovered precipitated asphaltenes are washed with precipitant and then recovered again via one or more of filtration or centrifugation.
4. The method of claim 1 , wherein the precipitated asphaltenes are redispersed in the solvent at a ratio in the range from 1:1 solvent/asphaltenes to 10:1 solvent/asphaltenes.
5. The method of claim 1 , wherein controlling the crude oil upstream process comprises controlling one or more of flow assurance and crude compatibility.
6. The method of claim 1 , wherein the crude oil upstream process comprises commingling of crude oil from different wells.
7. The method of claim 1 , wherein the crude oil upstream process comprises commingling of crude oil from different production zones.