7000psi mud pressures at 4.5km..., page-32

Sekret...

lol...example for you...

Take a drill string...connect little ballons allong the inside of it, all filled to the exact same diamater with air!

Lower the drill string vertically down the hole...now fill with water.

Will the ballons at the bottom be smaller than the ballons at the top?

In other words, do the ballons at the bottom have more pressure acting on them?

I think the confusion here is horizontal versus vertical movement.

With a horizonal pipe, sealed at each end and filled to the brim with water (ie no air pockets), we have a chamber exerting equal force along it's entire length...now, add water in one end under a certain pressure and it will come out at the other end with the exact same pressure...and all the way along the pipe, the pressure exerted on the walls will remain constant.

Now stand the pipe up virtically...we now have a graduating coefficient of varing pressure within the pipe, from say 14psi at the top to say 200psi at the bottom.

Add water to the top at a certain pressure, it will come out the bottom with the same pressure...PLUS...what ever additional pressure already existed at the bottom of the hole!

In other words, the introduction of pump pressure at the top effects the entire pipe equally from top to bottom...but does so in addition to the pressures that were already apparent.

In a horizontal pipe, the "constant" is pipe diamater AND "gravity", the latter of which is obviously a depth related variable.

In a vertical well the only "constant" is pipe diameter, whilst all else varies with depth.

So you are right, the pump exerts a constant pressure down the entire length of pipe...but in so doing, adds this additional pressure to those already existing at each level all the way down.

Cheers!