Determining the structural discontinuities in fractured carbonate reservoirs using FMS and VSP logs in the one of oil fields on West of Zagros

Abdullah Moradi , Bijan Maleki , Nazir Anvar Mafakheri
M.Sc. in oil exploration at Imam Khomeini International University
Associate professor at Imam Khomeini International University
Lecturer at department of petroleum engineering Soran University


A study is made into the structural discontinuities in an oil field to the west of the Zagros
mountain range, on the border between Iran and Iraq. Many oil reservoirs in the west of
Iran and in the Kurdistan Region of Iraq are of fractured carbonate type. Faults and folds
can change the structure of the reservoir. In such reservoirs, the study of the structural
discontinuity leads to the discovery of complex geological structures. This complexity
can impact on the discovery of a path to the reservoir. In one such oil field in western
Zagros the reservoir was expected to be located at a particular depth but the new drilling
well did not meet the reservoir. In this paper, Formation Micro Scanner (FMS) and
Vertical Seismic Profile (VSP) have been used to determine the location of the structural
discontinuities. Due to the low resolution of the VSP seismic data we find that it
discovers the major faults and the formations borders, but will not be able to determine
the small changes and complexity of the structure. Conversely, the FMS log(?) easily
recognizes these microstructures. Therefore, with a combination of large-scale VSP data
and small-scale FMS data we construct a 3D model. The results show that the well has
been cut by five faults that dip to the north with the exception of a first fault to the south
slope. To create the faults planes, AutoCAD software was also applied and the results are
shown in this study.

Key Words:
carbonate reservoirs
FMS log
VSP log
west of Zagros


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