Learning about well analysis?

[badatusrnames]

Originally posted by GT.....O?




Depends. Some reservoirs actually have a better decline if you flow them back faster. for example several slickwater fractured horizontal wells (oil) have gotten three times the IP rates and 2 overall production numbers from flowing back as hard and fast as possible. Getting those frac chemicals out of the reservoir like Friction reducer, Scale inhibitor, biocide and clay control out as soon as possible has proven to nearly DOUBLE the production of this particular formation.

my point being there are no written rules that apply to everything and every well/formation different.

Really? Where? Those chemicals are really a tiny proportion of the fluid in a job - it's really that massive amounts of water that you are loading the formation with than can cause formation damage. Some formations are more water sensitive than others of course.

A lot of damage in fracs (not slickwater though) is due to "gel" damage, which is polymer (guar) left behind in the formation. It can reduce permeability in your proppant pack something like 90%.

Flowing a frac back too hard and too quickly can result in proppant crushing, reducing proppant pack permeability. In some liquids rich plays (Duvernay or Granite Wash), drawing the well down too hard can also result in condensate drop out, creating a condensate bank and reduced (relative) permeability.

Data from the Eagle Ford and Duvernay have indicated that leaving a well shut in for a longer period of time (letting the frac marinate) have actually improved well results, not sure what the mechanism behind this is though.

Ultimately though, it really depends upon the specifics of the reservoir and the completion.

[badatusrnames]

Originally posted by Feruk

look at Arcan stock. There is nothing, not even out of control costs, that will make you go broke faster than high decline.

Great example. Management and BD got all horny looking at their investor presentations and their reported IP's, but spending an hour on GeoScout looking at actual well results told the true story pretty quickly.

[GT.....O?]

Originally posted by badatusrnames


Really? Where? Those chemicals are really a tiny proportion of the fluid in a job - it's really that massive amounts of water that you are loading the formation with than can cause formation damage. Some formations are more water sensitive than others of course.

A lot of damage in fracs (not slickwater though) is due to "gel" damage, which is polymer (guar) left behind in the formation. It can reduce permeability in your proppant pack something like 90%.

Flowing a frac back too hard and too quickly can result in proppant crushing, reducing proppant pack permeability. In some liquids rich plays (Duvernay or Granite Wash), drawing the well down too hard can also result in condensate drop out, creating a condensate bank and reduced (relative) permeability.

Data from the Eagle Ford and Duvernay have indicated that leaving a well shut in for a longer period of time (letting the frac marinate) have actually improved well results, not sure what the mechanism behind this is though.

Ultimately though, it really depends upon the specifics of the reservoir and the completion.

Have you ever seen what a couple drops of friction reducer does to an entire puddle of water?

I realize that these chemicals are only a small percentage, but after friction reducer is activated by the water its insane what only a few drops can do to a few hundred litres of water. its hard to understand unless you see it with your own eyes. which maybe you have or haven't...

Slickwater is totally different game then a linear or crosslinked gel, but it still does cause damage and the quicker you get the chemicals and water the better. Of course every formation is different and im not suggesting opening the choke to wide open, but usually you want to get all that crap out asap.

All clay control/buffer is, is salt water to help prevent clays from swelling up and decreasing your porosity.

Of course you are pressure charging the reservoir which always helps production as long as your water doesnt change your mobility preference of fluids/gases. Shale and sandstone reservoirs are completely different ball games. Shale is already so water bound that its not a big deal to leave water sitting in there for a while. sandstone can get allot of migrated clays which would severely hinder your production if you disturbed them.

Choosing gel vs slickwater is also totally dependent on rate and the type of frac you are looking to get. Slickwater tends to give very thin fractures but with a whole lot more complexity which is perfect for shale gas where you only really produce gas from within a few inches of your fracture. Gel on the other hand is good for low rates but the fractures tend to be wider and less complex.

I wouldnt choose a gel frac for those reasons unless absolutely necessary. There is just too much that can go wrong with a gelled frac, not enough breaker and your entire well is screwed.