 |
| Titel |
Geomechanical characterization of an Upper Triassic reservoir rock (Stuttgart Formation) in the NE German Basin (pilot site for CO2 storage at Ketzin, Germany) |
| VerfasserIn |
S. Klapperer, I. Moeck, T. Backers |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250060075
|
|
|
|
|
|
| Zusammenfassung |
| In order to investigate the influence of CO2storage in a 730-710 m deep saline aquifer of
Upper Triassic siliciclastic rock, a pilot project was set up at an anticlinal structure near the
city of Ketzin/Havel, west of Berlin. Three new wells were drilled and since June 2008, about
57,000 tons of CO2 (December 2011) have been injected. In 2011 an additional
observation well was drilled. Lithologically, the Upper Triassic, which is referred
asKeuper in Germany, consists of a multi-layered siliciclastic sequence ofpartly
anhydriticclaystone, siltstone, sandstone and evaporitic deposits (halite, anhydrite and
gypsum). Injection leads to a change of stress conditions in the reservoir and its faults
wherefore it is necessary to understand and quantify structural geology, stress regime and
geomechanical behavior from reservoir to cap rock. Notably, the interaction of
faults, lithologic units and stress field in a multi layered sedimentary system might
have a strong impact on fluid flow. The failure and faulting of the rock within a
stress field is strongly governed by rock mechanical properties. Therefore a suite
of geomechanical testing was undertaken on core material of reservoir rock. In
particular the parameters unconfined compressive strength (UCS), Young’s modulus E,
Poisson’s ratio ν, angle of internal friction φ and cohesion c were determined. The
results of the geomechanical tests show a surprisingly wide range of values within
one lithological unit. For the UCS the values vary between 8.1 and 177.5 MPa at
which high values were measured for highly cemented, medium grained sandstone
whereas very low test results were noted for weakly cemented, medium grained
sandstone. Quite low compressive strengths ranging between 15.8 and 19.8 MPa
was measured for clayey, fine sandy siltstone. Measurements on the partly well
cemented, medium grained sandstone indicate medium range values from 59 to
76.2 MPa. Other important properties for estimation of the mechanical behavior
of rock are the angle of internal friction φ and cohesion c, representing aspects
determining failure occurrence that can be expressed and illustrated by the Mohr
Coulomb failure criterion. As for the UCS there is also a wide range of values for φ
(4.06° to 36.98°) and c (10.45 MPa to 49.41 MPa) which differ distinctly within
similar lithologies. With respect to these differences further geomechanical tests in
combination with petrographic investigations will be in focus to evaluate the impact
of lithologal as well as lithofacial characteristics on geomechanical properties.
Thus the lithological and lithofacial heterogeneous characteristics of the Stuttgart
formation could influence significantly the geomechanical behavior and transmission
of stresses resulting from CO2 injection. Therefrom knowledge about these rock
mechanical properties helps to provide a save and long term injection and prevent leakage
scenarios. |
|
|
|
|
|
|