Method of predicting the concentration of asphaltenes using a first precipitant and correlation back to an asphaltene concentration measurement using a second precipitant

A method for characterizing asphaltene content of an oil sample, comprising:

• (a) obtaining the oil sample;
• (b) determining an optical spectrum of the oil sample;
• (c) removing asphaltenes from the oil sample to yield maltenes of the oil sample by precipitating asphaltenes using a first alkane precipitant, wherein the first alkane precipitant has a molecular formula with a number of carbon atoms greater than that of heptane;
• (d) determining an optical spectrum of the maltenes of the oil sample precipitated with the first alkane precipitant in (c);
• (e) determining spectral data related to asphaltenes of the oil sample by subtracting at least part of the optical spectrum of (d) from a corresponding part of the optical spectrum of (b);
• and
• (f) using a correlation that relates the spectral data as determined in (e) to concentration of asphaltenes in the oil sample as measured by precipitation using a second alkane precipitant, wherein the second alkane precipitant is different from the first alkane precipitant and has a molecular formula with a number of carbon atoms greater than that of heptane;
• and
• (g) using a correlation that relates the spectral data as determined in (e) to concentration of asphaltenes in the oil sample as measured by precipitation using a third alkane precipitant, wherein the third alkane precipitant has a molecular formula with a number of carbon atoms equal to or lower than heptane.