The image above represents radius of investigation.

To compute for the radius of investigation, five essential parameters are needed and these **parameters are permeability (k), porosity (φ), viscosity (μ), time (t) and total compressibility (C _{T}).**

The formula for calculating the radius of investigation:

r_{inv} = 0.0325 √[^{Kt }/ _{φμC}_{T}]

Where:

r_{inv} = Radius of Investigation

K = Permeability

φ = Porosity

μ = Viscosity

t = Time

C_{T} = Total Compressibility

Let’s solve an example;

Find the radius of investigation when the permeability is 25, porosity is 18, viscosity is 12, time is 22 and total compressibility is 37.

This implies that;

K = Permeability = 25

φ = Porosity =18

μ = Viscosity = 12

t = Time = 22

C_{T} = Total Compressibility = 37

r_{inv} = 0.0325 √[^{Kt }/ _{φμC}_{T}]

r_{inv} = 0.0325 √[^{25 x 22 }/ _{18 x 12 x 37}]

r_{inv} = 0.0325 √[^{25 x 22 }/ _{7992}]

r_{inv} = 0.0325 √[^{550 }/ _{7992}]

r_{inv} = 0.0325 √[0.068]

r_{inv} = 0.0325 [0.26]

r_{inv} = 0.0085

Therefore, the **radius of investigation **is **0.0085 ft.**