# Log-Log type curve analysis

Estimating reservoir parameter using Gringarten-Bourdet Type Curve excel spreadsheet for a vertical well in a homogeneous reservoir with constant WBS and skin factor

09-23-2021

The Gringarten-Bourdet Type Curve describes the pressure for a vertical well with constant WBS and skin in an infinite-acting reservoir.

The dimensionless pressure-derivative function $$P'_D$$ is plotted as a function of $$t_D/C_D$$ for various values of the correlating parameter $$C_De^{2s}$$

The $$P_D$$ and $$P'_D$$ type curves are in a single plot, permiting simultaneous type-curve analysis with both pressure and pressure-derivative curves and reducing the ambiguity.

Interpretation Process

1. Field data ($$\Delta P$$ and $$\Delta P'$$ vs. $$t$$ for DD, $$\Delta P$$ and $$\Delta P'$$ vs. $$\Delta t$$ or $$t_e$$ for BU ) are plotted on log-log scale

1. Identify the IARF period indicated by the horizontal portion od the derivative and the WBS-dominated period, indicated by the unit-slope portion of the derivative.

2. Match the data on the curves, then pick any convenient point (match point, red point)

1. Read $$\Delta P$$ and $$P_D$$ corresponding to the match point, read $$t$$ and $$t_D/C_D$$ corresponding to the match point and read the matching value of $$C_De^{2s}$$

1. Calculate well test parameters with the following equations

$k = \frac{141.2qB \mu}{h} \left(\frac{P_D}{\Delta P}\right)_{MP}$

$C_D = \frac{0.0002637k}{\phi\mu c_t r_{w}^2} \left(\frac{t}{t_D/C_D}\right)_{MP}$

$C_D = \frac{\phi c_t h r_{w}^2}{0.894} C_D$

$s = 0.5ln\left(\frac{C_De^{2s}}{C_D}\right)$

Example

Excel File

References

Lee, J. & Spivey, J. (2013) Applied Well Test Interpretation using the recommended procedure

### Citation

Vazquez (2021, Sept. 23). Chato Solutions: Log-Log type curve analysis. Retrieved from https://www.chatosolutions.com/posts/2021-09-23-ptatypecurves/
@misc{vazquez2021log-log,
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