Reservoir Characterization of the 9th Badenian Succession in the Mature Matzen Field, Austria

Perez, Javier¹; Rohler, Hendrik; Steckhan, Jan; and Mikuz, Thomas
¹[email protected]

Objectives
The main objectives of the study were the geological and petrophysical characterization of the 9th Badenian (Middle Miocene) succession in the Matzen Field and the identification of remaining hydrocarbon potential after more than 60 years of production.

Procedures
Subsurface data interpretation followed a sequence stratigraphy approach, obtaining a dense set of chronostratigraphic 3D seismic surfaces that were tied to well-to-well correlations in more than 700 wells across the field. Innovatively, an automated workflow was created to obtain a discrete log of litho-facies and corresponding stacking patterns for all wells, which was the basis for facies modeling. Additionally, 3D depositional facies were interpreted using spectral decomposition attributes to estimate distribution and connectivity of favorable reservoir qualities per sequence.

During the next stage, the challenge of distributing petrophysical properties across the static model, given the large amount of old wells with vintage log data, was overcome by calibrating modern porosity logs with core measurements and porosity derived from standard logs; as well as a good match between facies association and petrophysical rock types. Finally, a water saturation model was calculated from mercury intrusion capillary pressure data, obtaining rock quality dependent initial saturations used in field wide simulation. In addition, remaining oil saturations at well log scale were calculated to spot bypassed pay in producing wells and to visualize remaining oil potential in less efficiently swept areas.

Results
The main deliverable of the study is a 3D parameterized static model that was based on a detailed depositional facies configuration following a sequence stratigraphy approach; this model includes porosity, permeability, net to gross and water saturation distributions that characterize the reservoir’s areal distribution and vertical connectivity for further development. Furthermore, remaining hydrocarbon potential was interpreted in some of the producing wells, which were recommended for re-perforation.

Conclusions
The challenge of characterizing a very mature reservoir having vintage data was overcome by implementing modern workflows and detailed geological and petrophysical interpretations. An accurate facies distribution that shows the configuration of a reservoir depending on sea level fluctuations can be crucial to spot remaining oil potential at secondary recovery stage.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013