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Well Testing Toolbox

Interactive Tools

Engineering calculators and conversion utilities for field work.

Well Testing Symbols Library

$$\beta_g$$Dimensionless

Formation Volume Factor (Gas)

$$\beta_g = 0.0282 \frac{zT}{P}$$
$$\beta_o$$rb/stb

Formation Volume Factor (Oil)

$$\beta_o = \frac{V_{res}}{V_{stock}}$$
$$C_g$$psi⁻¹

Compressibility (Gas)

$$C_g = \frac{1}{P} - \frac{1}{z}(\frac{dz}{dP})$$
$$C_o$$psi⁻¹

Compressibility (Oil)

Undersaturated: Constant
$$C_w$$psi⁻¹

Compressibility (Water)

$$C_w \approx 3.0 \times 10^{-6}$$
$$C_f$$psi⁻¹

Compressibility (Formation)

$$C_f = \frac{1}{\phi}(\frac{d\phi}{dP})$$
$$C_t$$psi⁻¹

Compressibility (Total)

$$C_t = c_o S_o + c_w S_w + c_g S_g + c_f$$
$$h$$feet

Formation Thickness (Net Pay)

Vertical interval of pay
$$J$$bpd/psi

Productivity Index (PI)

$$J = \frac{q}{P_i - P_{wf}}$$
$$k$$mD

Formation Permeability

$$k = \frac{162.6 q B \mu}{m h}$$
$$P_{wf}$$psia

BH Flowing Pressure

Measured at Sandface
$$P_{ws}$$psia

BH Shut-in Pressure

Pressure during buildup
$$P_{1hr}$$psia

Pressure @ 1hr Shut-in

From straight line plot
$$S$$Dimensionless

Skin Factor

Calculation of damage/stim
$$\Delta P_{skin}$$psia

Pressure Drop (Skin)

$$\Delta P_s = 0.869 \cdot m \cdot S$$
$$z$$Dimensionless

Gas Deviation Factor

Real Gas Law correction
$$\phi$$% or fraction

Porosity

$$\phi = V_{pore} / V_{bulk}$$
$$\mu_o$$cp

Viscosity (Oil)

Resistance to flow
$$m$$ psi / log cycle

Gradient (Slope) of Build-up Plot

$$m = \frac{P_{1hr} - P_{ws}}{\log(\Delta t)}$$
$$P_i$$ psia

Initial Reservoir Pressure

Static reservoir pressure
$$P^*$$ psia

Extrapolated Pressure (X=1)

Pressure at infinite shut-in
$$Q_g$$ Mscfd

Production Rate (Gas)

$$Q_g = \frac{V_{gas}}{t}$$
$$Q_o$$ stobpd

Production Rate (Oil)

$$Q_o = \frac{\text{Bbls}}{t} \times \text{Factor}$$
$$r_w$$ ins or feet

Wellbore Radius (Open Hole)

Actual hole radius (not casing)
$$t$$ hours

Flowing Time

Total duration of flow
$$\delta t$$ hours

Shut-in Time

Time since well was closed
$$\mu_g$$ cp (centipoise)

Viscosity (Gas)

Low resistance fluid friction
$$\Delta P$$ psia

Total Pressure Drop (Drawdown)

$$\Delta P = P_i - P_{wf}$$
$$HR$$ Dimensionless

Horner Time Ratio

$$\frac{t + \Delta t}{\Delta t}$$