May 2015
Oilfield Technology
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21
petroleum system: the trap, reservoir, seal and charge. (See
area outlined in red in Figure 3).
There was no seismic data covering the area and the
assessment needed to be completed in less than two
weeks. There was data from one well, but it was just to the
north of the focus area from the existing Kudos field, so the
best approach was to start with a search of the scientific
literature to see what was publicly available. Typically,
most projects like this start with a Google keyword search,
or perhaps another online reference database like Scopus,
or going directly to the society and commercial publishers’
online tools to start a literature search. This approach
would have required that the search be performed outside
of Petrel and any relevant information found (e.g., maps,
figures and data) within the articles would have to be
extracted, georeferenced and then loaded individually
into Petrel. However, with the Geofacets Connector, this
workflow was conducted all within Petrel.
Using the ‘Find’ feature within Petrel, the Spatial filter
which geographically limited results to the project 2D
window, in addition to Geofacets-specific filters (Basin =
Southwest African Coastal Basin; Country = South Africa
and Namibia) refined the search results from more than
8000 items in the entire region to 72 maps and 32 articles.
Individual maps can be toggled on and off and by
applying additional filters (keyword, map type, data type,
date range, etc.) the results can be further refined to find
the most relevant information. In this case, limiting the
map type to ‘seismic survey’ reduced it to two maps, which
could then be explored in detail. Users can review detailed
information about the map and the article from which
the map was extracted, such as the article title, authors,
abstract, and map caption, all within Petrel.
Clicking on a link brings users to Geofacets where
they can view the original articles as read-only PDFs,
such as the one shown below from Marine and Petroleum
Geology. Skimming the article reveals additional data and
information including 2D seismic profiles, cross-sections
and stratigraphic columns, which could be imported into
Petrel.
Once all the relevant information was loaded,
Thiakalingam could start to examine the basin geology
and the structural features across the basin by comparing
the 2D seismic lines from the different publications. In this
project, 19 different seismic lines from 6 different articles
were included so that he could start to examine the lines to
identify trap, reservoir, seal and charge.
Using stratigraphic columns found in the articles, and
information from the one well to the north of the target
area, it was possible to confirm that presence and top
horizons of the potential seal and reservoir, without having
to purchase any seismic or well or seismic data. Here in the
interpretation window, a rough interpretation was made
identifying the seabed (blue line), seal (light green line) and
potential top of the reservoir unit (green line).
Loading maps and information found in the literature
made it possible to create a facies distribution map using
multiple interpretations from the literature, bringing it all
into Petrel to create a defendable 3D landscape identifying
the key elements of the petroleum system. In conducting
the analysis, the user is not limited to the imported data,
but can keep, amend or modify data in building a custom
interpretation appropriate to the business needs.
In addition, by interpreting all the 2D profiles brought
into the project from a variety of articles, and using the
mapping tool in Petrel, a 3D surface was created of the top
of the seal across the basin, which was then overlaid with a
thickness map of the seal formation found which was found
via the Geofacets Connector.
By combining the 3D depth map of the top surface of
the seal across the basin with the thickness map of the
seal across the basin, one can look at the 3D structure to
identify areas where the seal is thinnest and where it is
thickest, which can also be interpreted as areas of high and
low risk.
Finally it was necessary to evaluate the charge of the
source rock. Searching the Geofacets index for ‘source rock’
within the Southwest African Coastal Basin search results
produced five results of interest. After viewing the maps
and their associated data and articles, the most relevant
ones could be loaded into Petrel.
Looking at the charge map in context of the author’s
interpretation, the data indicates that there is good chance
for oil generation in the deeper part of the basin with
migration of the oil eastward. Pulling all the information
together, the case can be made that there is a potential
for presence of the four components of a petroleum
system: seal, reservoir, trap (stratigraphic and potentially
structural) and charge. Therefore, with the Geofacets
Connector, it was possible to undertake a high level
petroleum system evaluation, which identified areas of
high versus lower risk without acquiring seismic or well
data in this early-stage of exploration. In addition, the
assessment enabled the identification of target areas for
further investigation and one can be confident that the
dollars spent on acquiring data will be in the lower risk/
high potential areas of the basin.
With the initial analysis and modelling completed,
Phase II of Surenthar’s project will be to build a complete
3D Petroleum System Model using PetroMod to undertake
a more thorough risk assessment and ranking of the
potential prospects and play within the basin, as well
as assessment of migration pathways, and volumetric
calculations, etc.
Conclusion
The E&P industry faces a shortage of qualified and
experienced geoscientists, with more approaching
retirement age than joined the profession during the
1990s lull. Those on the job, therefore, need to do more
in less time. By speeding up the task of finding, reviewing
and importing scientific data into GIS, modelling and
analytic platforms, they can meet the need for accurate
assessments within short timeframes.
Note
*Petrel and Studio are registered trademarks of
Schlumberger.
