The Development of the Central Caspian Region; New Insights from 2-D and 3-D Structural Modeling

Robert Hooper, Jerry Drake, Kevin Dorrington, Eric Michael, Elchin Bagirov, and Terry Baganz
ConocoPhillips, Houston, TX

2-D and 3-D structural modelling of the Mid Caspian region raises several important issues about the development of the area most notably that Early Mesozoic (Triassic) stretching in the Donbas rift system to the north, and late Cenozoic sediment and crustal loading from the Caucasus Ranges to the south have significantly impacted the structural and thermal development of the Mid Caspian.

The structural configuration of the Mid Caspian region has changed significantly through time as the superposition of a series of deformation events, in large part related to Tethyan tectonics, modified initial geometries. Structural modeling confirms and quantifies the general observation from seismic data that there were two phases of Mesozoic inversion. The main phase of inversion was in the late Triassic during which 90%+ of the total shortening occurred. During the Mesozoic, following beveling at the top Triassic Unconformity, the basin dipped gently northward towards the axis of the early Triassic Donbas rift-system. A second phase of inversion in the Late Cretaceous, though contributing <10% to the overall shortening, had important implications for trap formation – late Cretaceous inversion created the first small closures in the Jurassic and Cretaceous sections. These closures were accentuated during the late Cenozoic, as a monocline progressively developed across the area as strata were tilted down to the southwest by loading from the developing Caucasus Ranges. Minor transpression during the late Cenozoic, created suites of steeply-dipping faults in the region of the monocline; these faults further accentuated the geometry of the traps.