During drilling and well completion, the drilling fluids may damage the formation nearby bottom hole and reduce its permeability. Stimulation treatment, such as fracturing and acidizing, in turn, may improve the permeability of this zone. As a result, a permeability variation zone will be probably formed around a well. It is one of the important reservoir engineering problems to determine the range of the zone and the degree of permeability variation. A transient well test interpretation model (composite sandstone reservoir mode D together with the new type curves are presented in this paper, which are based on the geological and development features of some China’s oilfields and can be used to determine the effects of damaged zone and outer boundary. In view of the nonuniqueness in manual matching, a computer automatic matching software is also established in accordance with the new type curves.

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