Transient Typecurve Analysis

Boundary-Dominated Match

Transient Match

Transient typecurves are particularly useful for data sets containing long-term transient flow. As opposed to the other modern typecurve methods that feature a single depletion stem, the transient module features a single transient stem. The multiple boundary-dominated flow stems correspond to reservoirs of different sizes. It hosts multiple superposition time functions from which to choose. This flexibility is offered for advanced users who have previously diagnosed the predominant flow regime (e.g., radial, linear, or boundary-dominated).

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

The transient 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 transient typecurves ”fan out" as different reD values for the radial model, and xeD values for the finite conductivity fracture model.

You can select the best matching typecurve, which provides an associated reD (or xeD) value. 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.

As determination of OGIP / OOIP is dependent on which reD (or xeD) value is selected, we don't recommend using the transient typecurve analysis to determine OGIP / OOIP. Instead, we suggest that the transient analysis be used to confirm the OGIP / OOIP estimates obtained from other analysis methods.

Transient Match

To obtain information about permeability and skin, we recommend that you focus on the transient stems of typecurves. These open on the left-side of the transient typecurve plot, converging to a single line for the radial model, and as a “fan” of different FCD values for the finite conductivity fracture model. For the radial model, the data is matched on the single stem. For the finite conductivity fracture model, you select the best matching typecurve, which provides an associated FCD value.

From the selection, Harmony calculates:

It should be noted that selecting a typecurve on the transient analysis is not a vital step for determining permeability and skin for the radial model (or permeability and fracture half length for the finite conductivity fracture model). As the data is moved about the plot, the permeability and skin (or fracture half length) are continuously updated on the Analysis tab.