Factors influencing oil recovery efficiency can generally be classified into two large categories: geological features of reservoirs and development and production technologies. As for reservoirs whose reserves have just been proved in exploration stage or in the initial stage of development

geological features of reservoirs are the main factors that influence oil recovery efficiency. Rational and comprehensive classification of oil reservoirs is based on application of analogue method and empirical data. There are various classification methods based on a single factor

such as trap types

physical properties of crude oil

rock types

poroperm characteristics

original reservoir drive mechanism

etc.. None of them

however

is suitable for estimating oil recovery efficiency. Principles of comprehensive reservoir classification are developed on the basis of statistics of geological features and recovery efficiency of each reservoir type by using the available data of more than 400 reservoirs. A new method of comprehensive reservoir classification is presented for estimating recovery efficiency.