Agarwal-Gardner Typecurve Analysis

Boundary-Dominated Match

Transient Match

The Agarwal-Gardner typecurve analysis (SPE 057916, 1998) is a practical tool that can easily estimate the gas (or oil) in-place, as well as reservoir permeability, skin effect, and fracture half-length (for hydraulically fractured wells). The accuracy of this analysis has been verified through numerical simulations. These modern decline typecurves represent advancement over Blasingame typecurves because a clearer distinction can be made between transient and boundary-dominated flow periods. This method also features curves containing derivative functions, similar to those used in the pressure transient literature, to aid in the matching process. The raw data derivative can also be used to assist in flow regime interpretation.

Note:   For information on the Agarwal-Gardner typecurve theory and equations, see Agarwal-Gardner Typecurve Analysis Theory.

The Agarwal-Gardner Typecurve analysis method uses the following models:

Boundary-Dominated Match

To obtain information about reserves and drainage areas, we recommend that you focus on the boundary-dominated (depletion) stems of the typecurves. These are located on the right-side of the plot, where each set of typecurves converges to a single line. The Agarwal-Gardner typecurve analysis does not require hyperbolic exponent values. Instead, the data is matched on the single depletion stem. As the data is moved about the plot, the OGIP / OOIP is continuously updated on the Analysis tab. 

For gas reservoirs whose fluid properties are strongly a function of pressure, the data points appear to "stretch" and "contract" as they are moved around the screen. This is because of the pseudo-time effect. Harmony recalculates gas properties at average reservoir pressures based on the calculated OGIP from the typecurve match. As the match is modified, OGIP, average reservoir pressure and material balance pseudo-time are automatically recalculated, and the data points are repositioned accordingly.

Transient Match

To obtain information about permeability and skin, we recommend that you focus on the transient stems of the typecurves. On the Agarwal-Gardner typecurve plot, these appear on the left-side of the plot as a “fan” of different reD values for the radial and water-drive models, re / xf values for the fracture model. Select the typecurve that best matches the data; this provides an associated reD (or re / xf) value.

From the selection, Harmony calculates: