Abstract: The Ordovician reservoir in Tahe oilfield is characterized by strong heterogeneity, developed fractures and vugs, complicated oil-water relation, no uniform oil-water interface. Based on the logging evaluation and formation testing data, as well as statistical log response characteristics from lots of oil and water intervals, this paper presents the crossplots of resistivity-porosity and gamma rayresistivity, P-S wave ratio approach, normal distribution approach and comprehensive discrimination approach to fluid property, by which proposes identification index for quantitative calculation of oil and water layers. The case study in Tahe oilfield shows that the coincidence rate for recognition of oil and water layers has reached above 75% for the purpose of making completion program and determinating reserves parameters.

Key words: Tarim basin, Tahe oilfield, fractured-vuggy reservoir, logging evaluation, crossplot, composite recognition