Is 3700 psi a good well pressure?

At the Kephart wells Lawrence County Pa.there two wells one the pressure is 1900 psi and the other is 3700psi does this sound good or bad?

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Permalink Reply by Kangoo on May 6, 2013 at 9:36am

Mike,

It's impossible to interpret pressure data without flow/production information.

Were both wells flowing at the time or were they shut in? If they were producing, at what rate were they flowing?

How long/how much gas have they been producing since the wells were brought online?

Permalink Reply by mike on May 6, 2013 at 12:55pm

Kangoo: shut in well are not in production

Permalink Reply by Trapper on May 6, 2013 at 2:18pm

Mike,

Are these both Marcellus or Utica or both?

Do you know the pressures @ the Patterson wells to compare?

Glenn

Permalink Reply by mike on May 6, 2013 at 3:41pm

No i do not but I will see what I can do

Permalink Reply by Kangoo on May 7, 2013 at 11:34am

Unfortunately pressure alone doesn't mean anything in unconventional reservoirs (in a conventional sandstone reservoir this is a different story).

Reason being that most shales are overpressured. The thing that makes an unconventional/shale well a good well is mostly not reservoir pressure but post frac productivity (meaning how much gas is produced per unit of pressure drop). This quantity is mainly determined by the conductivity of the fracs and also a property called 'matrix permeability' which describes how easy gas can flow between rock pores'.

The only way to get an idea about well productivity is to combine production and pressure information.

For example if you measured the pressure of the shut in well prior to the well being brought online for the first time and after maybe 100 days and then also had the production information (how many mmcf have been produced in this period) then one could roughly evaluate well performance. Of course there would still be lots of uncertainties, but at least one could make an educated guess. With just a single pressure measurement this could be the best well ever or the worst one and there is no way to know.

Permalink Reply by paleface on May 7, 2013 at 1:49pm

 Kangoo isn't the pressure gas?

Permalink Reply by Kangoo on May 8, 2013 at 4:33am

Paleface, normal pressure in subsoil reservoirs is sea water hydrostatics, which is related to the depositional environment (meaning the sediments were deposited in a marine environment). Normal pressure is a gradient of approx 0.43 psi/ft.

Especially in many shale plays pressure gradients are higher than this, which is related to the burrying and maturation of hydrocarbons and the fact that migration was limited due to the low interporous conductivity.

However there are also many overpressured aquifers (which only produce salt water) around the world, so pressure alone isn't related to gas or hydrocarbons in general (to answer your questions).

As mentioned in my reply before, what makes a well successful is productivity and this is a factor independent of reservoir pressure.

All being equal (meaning both wells have the same productivity index) the well with higher pressure will produce more hydrocarbons (which is what can be seen in the Utica towards the western edge, where production rates are decreasing due to lower reservoir pressure).

However pressure alone without considering well productivity doesn't allow you to determine how good a well is.

Permalink Reply by Trapper on May 6, 2013 at 3:59pm
Thanks mike.
Permalink Reply by Brian Powers on May 7, 2013 at 8:27am

mike -

knowing the depth at which this pressure was measure is important. Given your surface gathering system design, either well in your query could potentially be productive.

 

Brian

Permalink Reply by mike on May 7, 2013 at 8:46am

This pressure was measure@ the well head.

Permalink Reply by Joseph-Ohio on May 8, 2013 at 6:26am

3700 psi will support a static column of water 8534.637 feet.

When attempting to calculate if the pressure is adequate to lift a flowing fluid from underground one must also consider / accommodate pipe line pressure losses due to friction (and fittings) which will vary with flow rate (gallons per minute or gpm).

There is also the viscosity and the specific gravity of the flowing fluid to compensate for.

Generally speaking 3700 psi is alot of pressure and nothing to play with (don't think it would be wise for instance to stand in front of a discharge from say a pipe leak - it could really ruin an otherwise beautiful weekend - could be considered a lethal service pressure in my books).

Fluid temperature would also contribute to hazard - you know applying the hot knife cutting through butter principal.

BTW is that a flow pressure or static pressure ?  Also, I assume it's measured at the upcomer and not frac pressure - is that correct ?

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