Downhole determination of asphaltene content

摘要

A system and method for determining the asphaltene content of a downhole oil sample are provided. In one example, the method includes obtaining a hydrocarbon sample from a hydrocarbon formation of a reservoir at a given depth using a downhole tool. A liquid phase of the hydrocarbon sample is isolated within the downhole tool and the liquid phase is subjected to downhole analysis within the downhole tool to create a chromatography sample. The downhole analysis is based at least partially on size exclusion chromatography. A first property of the chromatography sample is measured to obtain a measured value, and a second property of the chromatography sample is estimated based on the measured value and known calibration curves.

主权项

1. 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; andestimating at least one property of the filtered liquid oil/solvent mixture using the control module and the measured value.