oilfield question

[okieboy]

I've worked in oilfield for 13 years, but heres my Q: There is a rig that is drilling twice. the first one is a DISPOSAL well, the second, an oil well. What is exact purpous for disposal well? Is it to just dump saltwater into, from the actual oil well? That seems expensive, just to get rid of it. -or do they go back and use the waste water later, to help stimulate the OIL well. A reply would be appreciated. Thanx!! -Rick-

 

[SNORGY]

The disposal well is for disposal of produced water.

Regulatory approval of the disposal well would likely have been contingent upon being able to demonstrate to the Regulator that the disposal zone cannot be in communication with the production zone. The Regulator would also have to know and approve the proposed formation and zone for the water injection.

To re-use the produced water is possible; it comes under what used to be termed "secondary oil recovery" and would be called a waterflood. Sometimes that water is treated, while other times it is simply reinjected. Again, if this is the intent, the Regulator would consider it an "injection" well and not a "disposal" well, and I think the terminology used would be very specific about that. In such instance, reinjection back into (or into communication with) the formation containing the oil would be approved.

So, if they are calling it a "disposal" well, I would be reasonably sure that the intent is to simply get rid of the produced water. With the disposal zone approved, it would be the most economically benign place to put it.

Regards,

SNORGY.

 

[zdas04]

Also, it is exceedingly rare for a disposal well to serve a single oil well. Generally water is piped or trucked into a disposal well from many wells. In an oil-producing state like Oklahoma, Texas, or New Mexico the disposal well would be regulated by the state oil guys, in other non-oil states it is regulated by the EPA. The regulations are amazingly complex and difficult to comply with. A disposal well is a very valuable asset.

David

 

[okieboy]

Thank you for your replies.

 

[DrillerNic]

Produced Water Reinjection (PWRI- the industry loves it's acronyms doesn't it?) is a bit unusual and also a bit hard: unless all of the oil has been removed from the water (down to a few PPM), you get emulsions forming during the injection and gradual loss of injectivity as the formation essentially gums up.

Also, if you are injecting new water as pressure support or water flood (they are similar but separate things), the thermal difference between the injected water and the formation means you get fracturing in the injection well, increasing injectivity, which is good.

Of course, in certain areas, water may not be easily avaialble, so produced water is better than nothing.

The other thing they might be looking to dispose of down the disposal well is cuttings, especailly oil based mud contaminated cuttings: depending upon the local regulations, slurrification & injection of OBM cuttings might be the only cost effective disposal route.