The image above represents diffusivity constant.

To compute for the diffusivity constant, four essential parameters are needed and these parameters are **pemerability (k), porosity (φ), viscosity (μ) and total compressibility (C _{T}).**

The formula for calculating diffusivity constant:

η = ^{0.000263k} / _{φμCT}

Where;

η = Diffusivity Constant

k = Permeability

φ = Porosity

μ = Viscosity

C_{T} = Total Compressibility

Let’s solve an example;

Find the diffusivity constant where the permeability is 12, porosity is 9, viscosity is 7 and total compressibility is 11.

This implies that;

k = Permeability = 12

φ = Porosity = 9

μ = Viscosity = 7

C_{T} = Total Compressibility = 11

η = ^{0.000263k} / _{ φμCT}

η = ^{0.000263 x 12} / _{9 x 7 x 11}

η = ^{0.003156} / _{693}

η = 0.000004554112554112554

Therefore, the **diffusivity constant **is **0.000004554112554112554**.

**Calculating the Permeability when the Diffusivity Constant, Porosity, Viscosity and Total Compressibility is Given.**

k = ^{n x φμCT} / _{0.000263}

Where;

k = Permeability

η = Diffusivity Constant

φ = Porosity

μ = Viscosity

C_{T} = Total Compressibility

Let’s solve an example;

Find the permeability where the diffusivity constant is 24, porosity is 10, viscosity is 5 and total compressibility is 13.

This implies that;

η = Diffusivity Constant = 24

φ = Porosity = 10

μ = Viscosity = 5

C_{T} = Total Compressibility = 13

k = ^{n x φμCT} / _{0.000263}

k = ^{24 x 10 x 5 x 13} / _{0.000263}

k = ^{15600} / _{0.000263}

k = 59315589.3536

Therefore, the **permeability** is **59315589.3536**.

**Calculating the Porosity when the Diffusivity Constant, Permeability, Viscosity and Total Compressibility is Given.**

φ = ^{0.000263k} / _{nμCT}

Where;

φ = Porosity

k = Permeability

η = Diffusivity Constant

μ = Viscosity

C_{T} = Total Compressibility

Let’s solve an example;

Find the porosity where the diffusivity constant is 28, permeability is 8, viscosity is 12 and total compressibility is 18.

This implies that;

k = Permeability = 8

η = Diffusivity Constant = 28

μ = Viscosity = 12

C_{T} = Total Compressibility = 18

φ = ^{0.000263k} / _{nμCT}

φ = ^{0.000263 x 8} / _{28 x 12 x 18}

φ = ^{0.002104} / _{6048}

φ = 3.478e-7

Therefore, the **porosity **is **3.47e-7.**

**Calculating the Viscosity when the Diffusivity Constant, Permeability, Porosity and Total Compressibility is Given.**

μ = ^{0.000263k} / _{nφCT}

Where;

μ = Viscosity

k = Permeability

η = Diffusivity Constant

φ = Porosity

C_{T} = Total Compressibility

Let’s solve an example;

Find the viscosity where the diffusivity constant is 30, permeability is 15, porosity is 6 and total compressibility is 21.

This implies that;

k = Permeability = 15

η = Diffusivity Constant = 30

φ = Porosity = 6

C_{T} = Total Compressibility = 21

μ = ^{0.000263k} / _{nφCT}

μ = ^{0.000263 x 15} / _{30 x 6 x 21}

μ = ^{0.003945} / _{3780}

μ = 1.04e-6

Therefore, the **viscosity **is **1.04e-6.**

**Calculating the Total Compressibility when the Diffusivity Constant, Permeability, Porosity and Viscosity is Given.**

C_{T} = ^{0.000263k} / _{nφμ}

Where;

C_{T} = Total Compressibility

k = Permeability

η = Diffusivity Constant

φ = Porosity

μ = Viscosity

Let’s solve an example;

Find the total compressibility where the diffusivity constant is 19, permeability is 14, porosity is 11 and viscosity is 4.

This implies that;

k = Permeability = 14

η = Diffusivity Constant = 19

φ = Porosity = 11

μ = Viscosity = 4

C_{T} = ^{0.000263k} / _{nφμ}

C_{T} = ^{0.000263 x 14} / _{19 x 11 x 4}

C_{T} = ^{0.0003682} / _{836}

C_{T} = 4.04e-7

Therefore, the **total compressibility **is **4.04e-7.**

Nickzom Calculator – **The Calculator Encyclopedia** is capable of calculating the diffusivity constant.

To get the answer and workings of the diffusivity constant using the **Nickzom Calculator – The Calculator Encyclopedia. **First, you need to obtain the app.

You can get this app via any of these means:

**Web** – https://www.nickzom.org/calculator-plus

To get access to the **professional **version via web, you need to **register** and **subscribe **for** NGN 1,500 **per** annum** to have utter access to all functionalities.

You can also try the **demo **version via https://www.nickzom.org/calculator

**Android (Paid)** – https://play.google.com/store/apps/details?id=org.nickzom.nickzomcalculator

**Android (Free)** – https://play.google.com/store/apps/details?id=com.nickzom.nickzomcalculator

**Apple (Paid)** – https://itunes.apple.com/us/app/nickzom-calculator/id1331162702?mt=8

Once, you have obtained the calculator encyclopedia app, proceed to the **Calculator Map, **then click on **Petroleum **under **Engineering**

Now, Click on **Well Testing**** **under **Petroleum**

Now, Click on **Diffusivity Constant **under **Well Testing**

The screenshot below displays the page or activity to enter your value, to get the answer for the diffusivity constant according to the respective parameter which are the **pemerability (k), porosity (φ), viscosity (μ) and total compressibility (C _{T}).**

Now, enter the value appropriately and accordingly for the parameter as required by the **pemerability (k)** is **12**,** porosity (φ)** is **9**,** viscosity (μ)** is **7**** and total compressibility (C _{T}) **is

**11.**

Finally, Click on Calculate

As you can see from the screenshot above, **Nickzom Calculator**– The Calculator Encyclopedia solves for the diffusivity constant and presents the formula, workings and steps too.