Infinite Acting Radial flow in Coventional Decline Curve Analysis (DCA)

[Chee Koh Peh]

Guys,

Okay for your academics out there here is a real technical question.......

We know that DCA is inapplicable for Infinite Acting Radial flow (i.e. non stabilized flow/transient/non pseudosteady steady state (PSS) flow).

Can anyone tell me how this violates the analytical solution proposed by Arps i.e. the solution to the differential generalized hyperbolic equation?

My understanding of PSS, is that under pseudosteady state flow, the difference between the flowing wellbore pressure and the average reservoir pressure in the drainage volume is constant.

Thus one of the boundary conditions to Arps solution to the differential generalized hyperbolic equation, appears to be constant pressure. Thus non PSS would appear to violate the boundary conditions necessary to solve the differential generalized hyperbolic equation.

Is this correct?

Thanks Guys, much appreciated!

Chee Koh Peh!

[vinomarky]

Sorry - I'd have to sit down with pencil and paper to really think it through, and don't have the inclination right now ;-)

What I CAN offer is that there has been some recent work (I believe if not in a paper already, soon to be in one from Fekete) that basically says a decline exponent of 2.0 (where 'normal' decline parameters should not go over 1.0) is a close approximation to transient flow. In fact they are using this to help characterize tight gas declines - from assume drainage radius and perm/poro they calculate time to reach boundary against which they use exponent of 2.0 until boundary 'seen' then something less than 1 (ie 0.6) after this

Hope this helps.

[darcyoil]

Heh ! heh ! Cheeky...I like it. A simple way around is RTA.