Abstract: Using geochemical log data from reservoirs to quantitatively evaluate crude oil properties can be as a guide for field quick evaluation of commercial value of reservoir rocks and timely taking reasonable measures in reservoir protection. The method for evaluating crude oil properties by utilizing Sanfeng petrologic pyrolysis data, statistical equations for establishing crude density and viscosity by production rate index and distinguishing crude oil types by bright spot index were discussed on the basis of Tarim basin's reservoir petrologic pyrolysis data, drill-stem testing and completion well test results. Good effectiveness was achieved by them, which offers reliable basis for making full use of the technical advantage of geochemical log and for hydrocarbon prospecting in Tarim basin.

Key words: Geochemical log, Rock, Pyrolysis, 0il property, Tarim basin