Enhanced Gas Recovery (EGR)

[karakurt2]

Dear Colleagues!

I would like to make survey of world experience applied to enhance gas recovery from reservoir on the final stage of exploitation. Could you suggest suitable literature? Where can I take classification of EGR methods? It would be nice to examine one or more specific examples on the real gas fields used in the foreign countries.

Alexander.

[cpeira]

Dear karakurt2 , generally speaking....EGR method is is not so popular, as Gas can be produced untill reservoir pressure is nearer to or just above surface atmospheric pressure. there is no problem of Mobility ratio consideration and gas/water break through problem as in Oil reservoir.
What is the general concept of EOR, in Oil reservoir
1. Displace the Oil by high viscosity Displacing fluid (Like polymer)
2. Make Mobility ratio leass by reducing the viscosity of Oil by Surfactant
3. Inject miscible gas to reduce Viscosity of Oil and make it Light
4. Increase temperature of reservoir to make the oil thin by huff n Puff, Steam flooding, Fire flooding etc.

But when we talk with gas reservoir, What method we should use...

1. Inject a gas which will displace the natural gas in the reservoir ( methane, Ethane etc ) by a gas of less commercial value and aboudantly available such as... Nitrogen, carbon dioxide, Flue gas etc.

Pl go through the literature I am sending the link.

[link Point to another website Only the registered members can access]

[link Point to another website Only the registered members can access]

[link Point to another website Only the registered members can access]

[karakurt2]

Thank you very much, cpeira, for quick and complete reply. I'm looked through Walker thesis. It seems that this work is close enough to my interests. At least I can start to write text based on this paper. Maybe I'll involve several other publications later. I appreciate you for your assistance.

[jisaav]

very detailed cpeira...

Great!

[vergatario]

It would be nice to investigate what sort of procedures or process you can use to recover or increase the recovery in gas fields subject to weater influx. The recovery in these reservoirs tend to be low.

[karakurt2]

Dear Colleagues!

I cannot understand what means under the following sentance:

"In volumetric reservoirs, compression decreases abandonment pressure..."

or

"The conventional approach to achieve additional recovery is compression..."

For me this is tautology, I doesnt see how this is phenomena of compression applied to increase recovery of volumetric reservoir. If author means on surface comressor facility, they used for hydrocarbon transport, I doesnt think so. Could you explain in other words the primary method to improve recovery from volumetric gas reservoirs?

[kochichiro]

I can say only few things about self-claimed EGR methods:
1. In volumetric gas reservoir only option is compressing gas on the wellhead. Thus you are making vacuum on wellhead and pumping gas until you reach 99 % of recovery. But gas consumption for the compressing may exceed it producing potential.
2. In water drive reservoirs it was claimed that large pressure drawdown will make reservoir to behave like volumetric drive. So you can reach EGR by larger pressure drawdown in the beginning of production. But these conclusions are misleading - you can check this by yourself if you’ll run reservoir simulation of the simplest water-drive gas reservoir. Make different scenarios with different wellhead pressures. In the middle-time you’ll receive more cumulative production with lower pressure scenario, but in the end lower pressure scenario will give less gas cumulative production than the higher pressure scenario, and far much water production.
3. In wet gas reservoirs one can install cooling system to increase production of the gasoline.
4. In gas-condensate reservoir only option is gas-cycling for new fields, and hydraulic fracturing to fight with condensate banking in near wellbore region in mature fields.

[Yengineer]

I have not heard about EGR. Well, until now......
What I have heard and taught are to ask and try to answer these questions:

• what kind of reservoir is it. Dry? Retrograde? or maybe volatile oil?
  
  Fluid analysis, production data can answer these questions.
• What is the reservoir that I am dealing with? Size, quality, behavior.
  
  Geology and seismic, core analysis, logs, well testing and production data can help you to understand that.
• What is the best exploitation/development strategy under the current economics and government regulation? Stimulation? Well spacing? Horizontal or vertical? Compression and other surface facility considerations?

Now here the ways goes in different directions depending on expertise, equipment etc. But well known methods are:

• Stimulation. ranging from small skin bypass jobs to massive, deep reaching fracs.
• Close spacing or horizontal well for tight reservoirs
• Gas cycling on retrograde rervs
• Maximum production to "outrun" the water in reservoirs with active water drive. If not possible fight the water by using cement. chemicals etc
• Wellbore optimisation (including artificial lift) and/or adding compression when the wells cannot flow against the pipeline pressure.

And thats it. No flood, no EGR and things like that.

[kochichiro]

You see, I think our friend karakurt2 from Russia. When I was in Gazprom, it authorities called all reservoir stimulation methods - Enhanced Gas Recovery/Secondary Gas Recovery Methods or so. That is why he is using so strange terminology

[Shakespear]

I would also recommend viewing the Tues. or Wed. (not sure) lecture by Whitson that is mentioned in the PVT EOS thread. In it he discusses strategies of doing a gas flood. I think you will get some very good practical information from what he says.

[karakurt2]

Yes, you are perfectly right, I am employed in Gazprom. I need to make survey of reservoir stimulation methos used in the world to improve recovery from volumetric carbonate reservoirs. It is the kind of reservoirs that exploited in our company. In fact most of resevoirs are close enogh to abandonment condition. For example, the recovery from Vyngapurovskoe field is 86% and the recovery from Medvejie field is 83%. These are huge depletion drive reservoirs. I heard about hydraulic fracturing or offshoot wells used to achieve additional production, but never meet with such methods as water injection or coproduction. I am not sure that they are typical for gas reservoirs. I learn a lot of new things for last month. Thank you very much for support of the discussion, your replies will help me compile full picture in my mind.

[kochichiro]

Wow, such good English in Gazprom, I impressed. This world is really changing
So, when we talk about Gazprom reservoirs first of all you must check production history, because recovery may be underestimated/overestimated. And all stimulation methods require sufficient reserves to prove them.
Carbonate reservoirs are always naturally fractured so they are subject of geomechanics, i.e. the most of fractures initially produced now are closed. That is why recovery from carbonate reservoirs is always lower then sandstones one.
There are two possible ways for stimulation:
1. Cheap and simple – massive acidizing with formation of wormholes and fractures.
2. Expensive and time consuming – hydraulic fracturing with large propped fracture.