Reservoir geochemistry has a practical application in petroleum exploration. A typical Paleozoic carbonate oilfield was selected from the Tabei Uplift of the Tarim Basin (northwestern China) to exhibit the method, application, and exploration implications of reservoir geochemistry. Oil-oil correlation indicates that all oils analyzed in this study belong to one single oil group. The overall oil migration direction traced by selected organic molecular markers is from the southern to the northern regions of the Halahatang region. The source kitchen for current oil accumulations in the carbonate reservoir is predicted to locate to the south of this oilfield, most likely between the Awati and Manjiaer depressions. Based on the characteristics of hydrocarbon-bearing inclusions and the histograms of the homogenization temperatures (T-h) and ice-melting temperatures of associated aqueous inclusions, the oil charging temperatures were obtained. The stratigraphic-burial and geothermal histories for representative individual well were reconstructed using one-dimensional basin modeling. We concluded that the Paleozoic oil reservoir has been charged twice during its oil charging history: first from 419 to 410 Ma and second from 16 to 8 Ma. The preservation conditions for early filling oil accumulations and the mixture of oils charged during the two filling phases have controlled the density and chemical compositions of present oil accumulations. The filling points and preferential pathway indicated by isopleth maps of molecular geochemical indicators are highly indicative of oil reservoirs with high yields. It is concluded that reservoir geochemistry can be utilized, not only to determine oil migration direction and to predict the location of source kitchens, but also for favorable charging pathway and potentially prolific prospecting zones. This study suggests that traps in the southern region along the preferred oil charging pathway into the Halahatang Oilfield could be the most favorable targets for further oil exploration in this region.