Typical curves and their analysis method for well test data without radial flow response

Abstract

The radial flow response does not exhibit after a long time testing for the low and ultra-low permeability reservoirs. In this case, it is difficult to determine the formation parameters effectively by using the conventional Gringarten-Bourdet's typical curve method. Based on a short-time asymptotic solution of homogeneous infinite well testing model, the relation between the dimensionless time and bottom pressure and the combination parameters of dimensionless wellbore storage coefficient and skin factor (ζ function) was obtained. A new type of early-time transient well testing interpretation type curve was constructed by using the dimensionless bottom pressure and ζ function, which can reduce the non unique solution problem of early-time transient well testing data analysis. The homogeneous Darcy flow model and homogeneous non-Darcy flow model considering the threshold pressure gradient were established to construct the new type curves. The characteristics and asymptotics of the above two kinds of type curves were also discussed. The results showed that compared with the conventional type curves the two new kinds of type curves were more sensitive to the parameter changes in homogenous model, which would effectively reduce the non unique solution problem of the well testing interpretation.