It is hard to reliablely estimate recoverable resources of tight oil by means of conventional resource evaluation methods due to the abnormal features of unconventional oil and gas accumulation.Through the study of the productive tight oil play in the B

12

interval of Wolfcamp Formation in the Permian Basin of North America

we proposed a new me- thod for evaluating recoverable tight oil resources in the Permian Basin based on multiple regression analysis.In line with the correlation between the geological parameters of pay zones and the actual production of the tight oil play

a model for evaluating recoverable tight oil was established;then

the geological parameters and their corresponding influence coefficients were determined by correlation and multiple regression analyses

so as to get the calculation model for recoverable tight oil abundance in the study area.Finally

the volume of recoverable tight oil in the study area was worked out.After the detailed analysis of SJ area in the Permian Basin

the geological factors affecting the recovery of tight oil can be graded in terms of significance as follows: brittle mineral content

maturity

porosity and oil saturation

with the degree of significance decreasing from the beginning.Meanwhile

the correlation coefficient between the predicted yield by the model and the practical yield reaches 0.7885

signifying the reliability of the model

and the total volume of recoverable tight oil is 46.15 million tons.Since the tight oil evaluation model based on multiple regression corresponds directly with the production

after setting the constraints on production

we can also get to know that the recoverable volumes of Type Ⅰ

Ⅱ and Ⅲ tight oil are 0.44

24.83 and 18.69 million tons

respectively.In summary

the new model based on multiple regression analysis is more effective for assessing recoverable tight oil resources and thus its scope of application is broader.