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Chapter
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Fig. 3.E.4 – Loading Data: Define data source Fig. 3.E.5 – Loading Data: Define data format
Unlike for open-hole logs and despite several attempts in the past, as of today (2010) no
industry-standard ASCII format has emerged to execute the load with a click. In Canada the
EUB has published a format (PAS) for compulsory electronic submission of test data and
results, but this remains very oriented towards local legal procedures. So software packages
have to provide the engineer with the flexibility to interactively define the file format, in order
to cover the wide variety of existing files.
Originally, the amount of data was a real issue because of limited available memory running
under DOS, the cost of computer memory, and the fact that the size of the data arrays had to
be declared and set by the software programmers at compilation time. All these limitations
have gone. Today’s software can easily handle multiple gauges and volume of gauge data
acquired during a well test which is sometimes more than a million data points.
The recommended procedure is to load all data acquired from all gauges during the well test,
and not just a filtered subset. Filtering can always been applied later, on duplicate data sets.
However, things are changing with the spread of permanent downhole gauges and the
increased usage of production data in Pressure Transient and Rate Transient Analysis. The
amount of production data is one order of magnitude higher, and is much less smooth than a
typical buildup. Smart filters, such as wavelets, are increasingly required to reduce the volume
of the data, retaining any trends and significant changes and at the same time eliminate noise.
The processing of Permanent Downhole Gauge (PDG) data is covered in another chapter.
3.E.3
Quality Control
Quality Control is an essential part of the interpretation, too often overlooked in the past, it
includes:
Validation of the gauges: identification of failures, drift, clock failure, resolution, etc.
Identification of operational problems.
When applicable, identification and correction of tidal effects.
Discrimination of wellbore effects from reservoir effects.