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HYDROSCAN^®  - Case Example - ONSHORE

A major oil field in Germany is build up of a cretaceous sandstone reservoir situated in an anticlinal block-faulted trap structure in a depth range between 500 and 1,000 m. The 10-25m thick pay posses a highly variable permeability distribution between 0.1 - 2 Darcy.

The onshore field is productive since more than 70 years. To assure continuing constant field productivity it is a permanent task to compensate the decreasing quantities by enhanced oil recovery measures and exploration of potential new bypass-fields. Detailed geophysical investigations build a fundamental part of this strategy.

In 2008 and 2010 two ground-based seismo-electromagnetic HYDROSCAN survey campaigns have been conducted, covering different parts of the oil field.
From data acquisition and data processing the frequency spectra and the normalized seismo-EM spectral attribute HPP (HC Productivity Potential) are derived.

The Figure represents the HPP-distribution along a profile-line from central oil field in the west to outside the field in the east. Around the supposed edge an enlarged area is imaged.
For comparison the reservoir transmissibility, calculated from well data permeability and pay thickness, is displayed.

The geophysical seismo-EM measuring result allows the following geological conclusions:
 

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•    The obtained threshold-exceeding HPP-values are verifying that the sensitivity and signal-to-noise ratio was excellent to detect the oil occurrence, whereby the oil reservoir field is correctly identified

•    The oil/water (OWC) transition is clearly indicated around 10,200 m by strongly decreased HPP-values, the OWC shifted about 500 m from east to west compared to the former location due to 70 years of continuous oil withdrawal from the anticlinal trap

 •   A remarkable "hot spot" area of high to very high HPP-values is mapped around 8,800 m to 10,000 m, which is confirmed by single production wells exhibiting enhanced permeability in this zone; additional well bores are planned

•    In general the HPP trend within the oil field corresponds to the transmissibility increasing from 3 Darcy-meter in the central part to 30-40 Darcy-meter in the eastern part of the reservoir and therefore confirms the relative quantity correlation

•    At 11,400 m a small HPP anomaly zone was detected outside the main field and thus advising for further investigations in this prospective area in order to delineate a potential bypass-field