Patent ID: 8899107

Claim:
A method, comprising: operating a downhole tool positioned in a borehole extending into a subterranean hydrocarbon reservoir, wherein the downhole tool comprises a separator, a reservoir, a solvent disposed in the reservoir, a mixing chamber, a size-exclusion chromatography module, a detector, and a control module, and wherein operating the downhole tool in the borehole comprises: obtaining a sample from the reservoir; separating a liquid oil portion from the sample using the separator; mixing the liquid oil portion with the solvent in the mixing chamber to form a liquid oil/solvent mixture; filtering the liquid oil/solvent mixture in the size exclusion chromatography module to remove hydrocarbon components having a molar mass less than about 0.350 kg/mol; measuring the filtered liquid oil/solvent mixture using the detector to obtain a measured value; and estimating at least one property of the filtered liquid oil/solvent mixture using the control module and the measured value.