Asphaltene content and its spatial distribution in a reservoir containing crude oil is an important factor in determining the potential for formation damage and pipeline impairment, as well as planning for processing and refining of the oil. Exemplary uses include: reservoir modeling, development and depletion planning, pressure maintenance, and surface facilities management. A convenient method has been developed which uses two-dimensional NMR techniques during a temperature and/or pressure cycle to quantify the asphaltene content of the crude oil without the need for extracting the oil from the reservoir rock. The technique can be applied to core, down-hole logs, or, a combination of both.