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Hi guys!

Can anyone please explain to me what shale swelling is all about? How does it occur/factors contributing to shale swelling and ways to prevent it? I'm doing an assignment about the differences of clay swelling and shale swelling actually. I know what clay swelling is but shale swelling? This is the first time I've heard such term.

Enlighten me please. Thank you!

Shales that contain swelling clays will swell if they are wet long enough. This can be a serious problem in oil/gas well drilling since the swelling can result in getting the drill pipe stuck in the hole. If this happens the least that it is going to cost is the cost of the drilling rig etc while the pipe is getting unstuck and the worst case is having to abandon the well with the pipe and sometimes a down hole motor left in the well bore. Various mud additives are used to try to prevent the swelling of the clays but I am not familiar enough with those to say anything else about them except that on the wells on which I mud log we use 3-10% ABO (asphalt based oil) mixed with the drilling mud to control swelling.

Darryl

Hey Darryl!

Thank you so much for the reply!

Shale swelling is the same thing as clay swelling; when a fluid enters a reservoir that contains certain types of clay (such as smectite), the clays will expand, thereby decreasing the porosity and permeability of the reservoir in that aera and dmagaing the formation.

A good paper on the topic: Swelling Clays in Hydrocarbon Reservoirs: the Bad, the Less Bad,
and the Useful Z. (John) Zhou and David H.S. Law, Alberta Research Council, Edmonton, Alberta,
Canada