PE GATE : ESP introduction

Imagine, you are a Petroleum reservoir and you are giving oil to the several oil wells.

You are giving oil to all wells with lot of energy. After some time, you might be feel like, your energy is draining. Your energy is reducing with reducing fluid content from yourself. Like you are depleting along with your energy (pressure of reservoir is depleting.)

So, earlier you were delivering fluid to the surface, but as of now, you do not have sufficient energy to lift it to the surface of well.

So, you will deliver fluid to the level at which your energy permits. Right ?

Suppose, we have well of 10000 ft depth, and you can now only lift your fluid to only 5000 ft only.

So, 

How this fluid will cover remaining 5000 ft of distance ?

Any idea ?

(Hint for you, it will be helpful if some one else can do your help, to lift that fluid from you.)

And that lifting help is called Artificial lift.

Now think, how can we lift fluid from bottom to surface ?

Easiest way we can visualise is, if we have any instrument which can create suction, so that we can suck fluid like a vacuum cleaner downhole, than we can suck all oil accumulated there, and can deliver it to surface.

Image is taken from internet.

Lets install a vacuum cleaner downhole. Now it will suck oil from certain distance and can deliver it to the surface right ? (Assume it has that power, so that it can deliver to the surface).

That vacuum cleaner is our ESP.(Electrical Submersible Pump).

Now, as we can see, Vacuum cleaner has internal parts like, a rotor or impeller and that is driven by a motor. And to power that motar, we require electricity.

So,we make one tool, which has impeller and motor. We require electricity to power the motor, so we make arrangement to provide electricity conduit in form of electric cable.

We run cable from surface to downhole.

(So, we modified well head design also. So that is can accommodate cable.)

We make a hole on well head to pass electrical cable. 

So, here we use centrifugal type of pump.

But, is one single pump is sufficient to lift fluid ?

If we have higher depth of lifting, then we will require multiple pumps arranged in series.

So, we have multiple stages of pumps stacked in series, so that we can have enough lifting pressure (or head) to lift fluids to surface.

So, ESP is a multistage Centrifugal Electrically motor driven pump.

So, we put ESP above certain distance of fluid level of well, then it will suck fluids and provides energy to them (energy flow from electrical cable to motor (Mechanical) to impeller to fluids (kinetic energy to potential energy (with help of Diffuser))).

Now, in centrifugal pumps, we can not flow gases, because it creates problems. (Cavitation). 

And in our reservoir, we have always associated gases (which come out with oil always) and sometimes multiphase flow with gases. So, what we can do so that gas will not be directed to the pump ?

Yes, we can install one more device which can separate gas from our fluid. That device or instrument is called, Gas separator or Gas anchor.

So, Impeller and diffuser (Pump stages), motor, electrical cable and gas separator that are main sub surface components of an ESP.