PE GATE : EOR : Basic Concepts : Mobility

What determines mobility or ability to move fluids from one pore to another pore or inside porous media ?

First answer of all of us will be, Permeability. (Yes, that is main super hero for fluid to move.)

So, higher the Permeability of fluid, higher ability to move fluid.

Think about other factors.

For ability to move in restricted environments,(like porous media here), if our fluid is more Viscous, then it will have less ability to move. 

That is point where we all are agree.

So, we have two terms, one with positive relation with ability to move fluid (that is permeability), and one with negative relation with same (Viscocity).

So, if we want to define this ability to move fluid in one parameter, than can we do it ?

Well, we can do it in simple way.

Just make ability to move fluid proportional to permeability and inversely proportional to viscosity.

And that will be our new parameter, which is essentially representing ability of movement or ability of fluid to be mobile (That's Mobility).

So,

Mobility = (k)/(μ)

here, k is effective permeability of fluid.

And μ is dynamic viscosity of that same fluid.

Why we use effective permeability ?

Because generally in reservoir, we have more than one type of fluid. So we use term effective Permeability. (To include effect of another fluid also).

Mobility of human in Air (on no restrictions)

Next thing is, where we use this mobility term ?

1) To Calculate flow rate, we can use this term.

Think by yourself, what is essential things for a flow to happen ?

First thing is, fluid should be mobile. So, it should be have more mobility. (So, flow rate is proportional to mobility)

Another thing, potential. Generally all flows occur from high energy to low energy. So we required potential difference. Higher the potential difference, higher flow will be. (Flow rate is proportional to potential gradient)

So, flow rate,

Q = (Mobility)*(Potential gradient).

2) Mobility term is used in calculation of mobility ratio parameter. (Term which is useful in EOR efficiency calculations.

  

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