The Oil Drum

45 comments on Saudi Arabia's Ghawar Isn't Sinking (but has apparently moved)

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Darwinian on May 8, 2008 - 12:24pm

Well if subsidence is possible from removing something, then it is reasonable that putting something back in would restore it.

Dr. Joules, that completely ignores Khebab's point. That is the weight of the overburden rock. It is a lot easier to pump oil or water out that is under tremendous pressure than to push it back in. It is a lot easier to let 7000 feet of solid rock fall than it is to lift it.

Injection wells, from a link I posted yesterday, have an injection pressure of about 1500 PSI. Some of them in Ghawar may be slightly more but that is not even close to the amount of pressure it would take to lift 7000 feet of rock. Khebab says it would take 1000 bars, or about 14,500 psi. Someone on Drumbeats yesterday said it would be slightly less or about 1 psi per foot. But at any rate, 1500 PSI is not even near the pressure it would take to raise such a heavy load.

I would take the position that lifting 7000 feet of rock with an injection pump is an impossibility.

Ron Patterson

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alaska_ray on May 9, 2008 - 1:40am

My understanding is the lifting force is actually due to intergrain water sheets, which move by capillary action. This force is incredibly powerful--it can considerably multiply the measured pressure.

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NC on May 9, 2008 - 9:44am

Another thing to consider is the solute potential of material left in the rock. Even injecting sea water, if there are water soluble compounds (sulfur, acids, iron, etc.) in the field the water activity will want to equilibrate. Water will flow from a dilute solution to a concentrated solution until the concentration of solutes is balanced or the sources migrate away from the rock.

Plants grow through this mechanism. They raise the solute potential in cells (using any small molecule, salts, sugars, acids, proteins, etc), water flows in from outside, raising the internal pressure and forces the cell walls to physically deform/stretch in one direction along a fault zone in the cell walls. The power of osmotic potential can be very large, getting into the 1000's of PSI. Plant roots break granite rocks apart using this mechanism as they grow. I am not saying this mechanism is happening in this field, just that it shouldn't be discounted in a water drive oil field.

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elwoodelmore on May 9, 2008 - 8:57pm

according to wiki, this is the mechanism at work in ekofisk, mentioned below. subsidence due to solution cavitation. i have never heard of this happening in ghawar, but if bernstein is to be believed, it is not happening.