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Dynamic Data Analysis – v5.12.01 - © KAPPA 1988-2017
Chapte
r 4 – R ate Transient Analysis (RTA)- p152/743
The load option imports flat ASCII files, allows manual input, copy-paste from spreadsheets,
and increasingly input through links to databases or intermediate repositories using advanced
filtering tools.
After the load, the cumulative production is automatically calculated by integration of the
production history, and is displayed on the history plot together with the rate. Pressures is
loaded and displayed in the history plot.
Quality control is not as critical as in PTA, because wellbore effects are normally not dominant,
except when the pressure is recorded at surface. In this case, the validity of the well intake
curves used to correct the pressure to sandface during extraction can become a potential weak
point.
4.E.2
Editing data
Loaded data may be the result of careful post-processing after the data has been acquired, in
which case no or little editing may be needed. However, often the interpreter will gather data
of unequal quality from different sources. Pressures will often be acquired downhole in real
time or with a memory gauge or come from permanent gauges (PDG), while rates are mostly
measured at surface but in some cases, can also come from permanent measuring devices
downhole.
Beyond the usual cleaning of irrelevant data and the correction of load errors, the main
challenge is to end up with at least one coherent, synchronized set of rate and pressure data.
To get there the engineer may have to perform the following tasks:
Synchronise all data acquired electronically to the same reference time.
If rates are not loaded from a file, create the rate history by identifying the pressure
breaks and get the rate values from hard copy reports.
Refine the production history, when the time sampling of rate measurements is too crude.
Conversely, if the production history goes into useless detail, simplify the rate history to
reduce the CPU time required to run the models.
4.E.3
Extraction and diagnostics
Once the data have been synchronized and validated, the analysis itself will start. The time
range over which the extraction of the data will take place is defined and the following plots
are built by the software in addition to the history plot:
ARPS plot
Fetkovich type-curve plot
Fetkovich plot
Blasingame plot
Loglog plot
Normalized rate-cumulative plot
At extraction time the option to invoke a defined lift curve or flow correlation to correct the
pressure profile from the measurement depth to sandface can be chosen.