Publication Date

2013-09-13

Availability

Embargoed

Embargo Period

2015-09-12

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Marine Geology and Geophysics (Marine)

Date of Defense

2013-06-13

First Committee Member

Gregor P. Eberli

Second Committee Member

Larry C. Peterson

Third Committee Member

Mark Grasmueck

Fourth Committee Member

Jose Luis Massaferro

Fifth Committee Member

Klaas Verwer

Abstract

Mixed carbonate siliciclastic systems develop laterally and vertically complex sediment successions, which in turn complicate subsurface seismic interpretation and reservoir characterization. The key to developing conceptual and predictive models of these mixed systems is the documentation and understanding of the sedimentary and environmental processes controlling these depositional environments. For this purpose, subsurface or outcrop studies alone are not able to cover the full range of scales necessary to investigate the main controls on the system. Therefore this study takes an integrated approach, connecting detailed outcrop descriptions of geometries and lithofacies distribution within a sequence stratigraphic framework to the larger scale seismic architecture of the Quintuco - Vaca Muerta mixed carbonate siliciclastic system in the Neuquén Basin of Argentina. This study documents for the first time the lithofacies distribution of two classical exposures in connection with the stratal architecture observed from satellite and photo imagery and finds that carbonate-rich successions have a clear geometrical signature with steeper clinoform dips and more pronounced clinoform breaks than siliciclastic dominated intervals. Moreover due to the high acoustic velocities and densities, carbonate intervals represent high acoustic impedance and therefore are easily detectable in synthetic seismograms and compared seismic datasets. The alternations between carbonate and siliciclastic dominance follow the sequence stratigraphic framework and indicate a direct relation to fluctuating sea level. This pattern is driven by the efficiency of along-shelf sediment transport, which is accommodation space controlled. Main clastic sediment input occurs at times of high accommodation space, when currents along the shelf are strong enough to carry in material from the Andean volcanic arc. In times of decreasing accommodation space these current systems slow down and clastic input is reduced and the carbonate content increases. This cyclic driver of sea level oscillations can get overruled by regional climatic changes and localized tectonic uplift. A pure carbonate depositional environment developed in the Late Tithonian probably due to a shift to more arid climate with less weathering and erosion in the provenance areas leading to lower siliciclastic input. At the same time, tectonic uplift in the outcrop areas shifted the sedimentary system from a shelfal mixed system to a siliciclastic dominated nearshore environment in the Late Berriasian. Based on direct link to the seismic dataset, the two outcrop exposures prove to be time-equivalent successions to the lower prograding system in the main producing field area and developed in one large depocenter between the Tithonian to Late Berriasian, before a tectonic shift along a regional inversion feature created differential sedimentary systems in the western and eastern portion of the Neuquén Basin. This time–equivalence together with the strong similarities of seismic architecture make the documented outcrop lithofacies distributions key analogs for unconventional and conventional exploration in the eastern subsurface area of the Neuquén Basin.

Keywords

Mixed Systems; Facies Geometries; Sequence Stratigraphy; Seismic Modeling; Depositional Model

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