Fracture and
Sandstone Diagenesis of the Lance –
Malicse, Ariel1, Calum
Macaulay2, Candyce Beck-Brake3 (1) Bellaire Technology
Center, Houston, TX (2) Technology Applications & Research, Houston, TX (3)
Shell Exploration and Production, Houston, TX
The Lance and Upper Mesa Verde Formations
in the Pinedale region of
With the exception of barite, the host
sandstones and fractures follow the same paragenetic history. Calcite dominates
the fracture-fill, +/- barite and kaolinite. The calcites in cements and in
fractures have a similar range of carbon and oxygen isotopic compositions. In
contrast, the ä18O values of the calcareous paleosols are less negative and
ä13C values are variable. Paleosol calcite has an isotopic composition that is
distinctly different from pore-filling and fracture-filling calcite. Some
evidence exists that paleosol calcite may have been dissolved and
re-precipitated as cements and as fracture-fills during the burial history.
Fluid inclusion analyses indicate an
overlap in the homogenization temperatures of calcite cements and
fracture-filling calcite. Fluid inclusion analysis of barite further
constrained the fracture timing. The results of fluid inclusion analyses were
correlated with the burial history model for the study area. From this
correlation and the crosscutting relationships of authigenic minerals we have
reconstructed the timing of fracture development and re-opening.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California