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Chapte
r 4 – R ate Transient Analysis (RTA)- p159/743
4.F
RTA versus PTA
4.F.1
Introduction
The comparative table below shows a summary of the common and different aspects of the
PTA and RTA techniques.
The main aspects will be detailed later in this paragraph.
Pressure Transient Analysis
(PTA)
Rate Transient Analysis
(RTA)
Theoretical bases
Same equations, superposition, analytical and numerical model.
Some assumptions are, however, specific.
Time range
Hours, Days,
sometimes Weeks
Weeks, Months, Years
Periods of interest
Mostly shut-ins
Clean productions possible
Producing phases
But build-ups may be included
Data sources
Well test measurements
Formation tests
Permanent gauges (PDG)
Measured/allocated production
surface pressure readings
Permanent gauges (PDG)
Reservoir areas of interest
Whatever volume of
investigation during the test
and/or the shut-in
Well or group drainage area
The good old plot(s)
MDH, Horner
Arps
The good old type-curve(s)
McKinley, Gringarten
Fetkovich
Modern diagnostic plots
Loglog with Bourdet derivative
Loglog & Blasingame with
Bourdet derivative
Main flow regime of
interest
Main corresponding results
Infinite Acting Radial Flow
kh & skin
Pseudo-Steady State (PSS)
drainage area & shape factor
Diagnostic capability
High to very high
Average to low
Long term validity
Average to low
High to very high