Abstract: Modified isochronal well test plays an important role in productivity evaluation of gas field. For low permeability gas reservoir, it is difficult to keep the bottom hole flowing pressure stable in the stage of continuing flowing of gas well. At the same time, it is also difficult for coefficient B of turbulent flow equation with different time to maintain constant, hence the application of modified isochronal well test is confined. In this paper, the new method for processing of modified isochronal well test data for low permeability gas field was established. By application and case comparison, the results show that this method is more accurate and reliable than existing conventional approaches.

Key words: low permeability reservoir, gas reservoir, well testing, method