Drilling for oil

I searched on google on the process of drilling oil, and no results are given.


When a company pumps oil out of the ground, what fills up that space? Does water fill it up?

I was watching the Tusuami on CNN and recently wondered maby that could have a very little chance of it?


Thanks

I believe they pump saltwater/brine back into the void, at least in some drilling i am aware of at least.

They don't just leave a space, otherwise that would be a tad dodgy and asking for trouble.

Thanks stumason, I was wondering and thought sooner of later we will just concave in.

No worries, check out this link:

How Stuff Works: Oil Drilling

You might find this story interesting as it shows what disasters careless drilling can cause. Very odd story to say the least.

members.tripod.com...

Extracted oil is replaced with salt water, unfortunately, the salt water has been shown to cause earthquakes. Recently, oil companies agreed to environmentalists requests that they cut the amount of saline they pump into the earth to replace the black gold that has been taken out.

I wonder if the huge frenzy of drilling activity in the Aceh procence of Indonesia had anything to do with their recent and ongoing struggle with an angry earth. Maybe they've simpy drained that tectonic engine of too much oil, and now it's grinding and smoking, just like any engine would.

The only time any type of fluid is pumped back into a reservoir is when the driving pressure (the reservoir pressure) has decreased so much from production that the well can no longer produce at a pressure that will drive the oil up the wellbore. Then, if the oil company deems it profitable, they will do gas-drives (use gas to drive the oil), steam drives, water drives, and sometimes even a fire-drive. The oil company will not use salt water if the reservoir is not stable to salt water - they'll use fresh water in that case. But if it is a reservoir conducive to salt water then they'll use salt water.

There is no vast "void" left behind when oil is taken from a reservoir. Reservoirs are not big holes filled with oil. The oil is in the interstitial spaces of the permeable rock. (It is like sucking water out of a sponge.) So the only voids left behind are the microscopic holes in the rock. And if it is not a permeable zone, then reservoir is fractured so that the oil can have the fracture as a path to flow to the well. Along with fracturing there are several other production enhancement techniqes that can be used. For instance, acidizing will eat the matrix of the rock to cause an apparent increase in the permeability so that the oil trapped in the rock can flow out.

Now typically, what happens in a depleted oil well, is that the earth itself fills the tiny voids in the rock. You see on a typical oilwell you'll have the fluids stacked in the rocks just as they would be if they were sitting in a glass...lighter down to heavier. So you'll have a salt dome or shale that "caps" everything below it, then you'll have your gas zone, then you'll have your oil zone, and below that will be the water. As an oil zone is depleted the water below it starts rising...eventually the well starts making too much water to be profitable anymore, and then it is plugged and abandoned. By the way, this is what is starting to happen in the mideastern oilfields...they are beginning to have problems with water production.

what about the old days like 1800? when they pumped it out what happand ? what did they pump back in

They didn't. Once a well was deemed unprofitable they plugged and abandoned it (they pump the wellbore full of cement).

[edit on 1-1-2005 by Valhall]

thats a relief few would of thought they did nothing

The plugging and abandonment of wells is one of the more regulated aspects of the oil industry. The cement job on an abandon well has a lot of requirements it must meet because that plug is basically your permanent barrier to any bad junk (oil, gas, salt water) coming back up the wellbore and contaminating your fresh water table. So...there are stringent regulations on P&A operations.

thanks for the help but another question how long would the cemente take to dry cause it's under ground no light obviously in fact would it dry at all?

Yeah, it dries. The hydration and setting process of cement is an exothermic reaction (it makes heat, it doesn't take heat). Also, a cement slurry (i.e. before it turns to concrete) is thixotropic...meaning, if you don't keep it moving it starts setting up almost immediately. So what happens is the cement slurry is pumped to whatever position it is needed in the well (whether it be the initial cement job between the production casing and the wellbore or a P&A job) and when they stop pumping it it immediately begins its transition to a gel state (i.e. something between a fluid and solid) and from there it turns to concrete very rapidly. Now, as just about anyone in the construction business will tell you, it takes about 27 days for concrete to get to its permanent strength, but within hours it will be 1500-3000 psi compressive strength.

[edit on 1-1-2005 by Valhall]

Also...it's not cold in a wellbore...It's HOT! And the deeper the well, the hotter it is, so you're actually talking about cementing at hotter temperatures than at the surface.

i never knew the deeper ya went into a well the hotter cool so it drys easy?

cool how would they pump it just drop it in or somthing?

No, they pump it with big pumps.

Concerning the temperature, what you're not taking into account is the deeper you drill into the earth the higher the overburden pressure you encounter (that's the force of the earth above you pushing down on you). Because the pressure increases, the temperature increases.

In the deeper wells they're drilling these days, bottom hole temperatures of 500 F are not uncommon.

[edit on 1-1-2005 by Valhall]

so 500 f is like 250 degress and thats over boil;ing tempreture but would'nt conreate somtimes dry inside the tubes?

As long as the cement slurry is moving it won't set up. So, what happens is you calculate the volume you need to put the cement right where you want it and you pump that much and stop. Once you stop the cement starts setting up.

Yes, in an initial cement job (where you are placing the cement in between the casing and the reservoir) some of the cement is left in the pipe at what is called the "shoe". You drill through this and keep going (unless you're already where you want to be - in that case, that cement just stays there.

In a plug and abandon, you are putting the cement in the pipe on purpose and you just plug up the pipe - this doesn't mean you have pumped the entire pipe full of cement, you can just do a portion of it some where above the producing zone and below the water table.

Ok, I have a question about oil. My understanding is that oil is concidered a lubricant. That being the case, should we be taking it out of the earths crust? I would think that if there was less or no more lubricant then the earths crust would not be able to move as smoothly when it needed to resulting in nasty earthquakes. What do you think?