A Comparison of Two Early Miocene Carbonate Margins: The Zhujiang Carbonate Platform (Subsurface, South China Sea) and the Pirinç Platform (Outcrop, Southern Turkey)
P. Bassant, F. Van Buchem, A. Strasser, A. Lomando, 2004. "A Comparison of Two Early Miocene Carbonate Margins: The Zhujiang Carbonate Platform (Subsurface, South China Sea) and the Pirinç Platform (Outcrop, Southern Turkey)", Integration of Outcrop and Modern Analogs in Reservoir Modeling, G. Michael Grammer, Paul M. “Mitch” Harris, Gregor P. Eberli
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Early Miocene carbonate platform complexes have been the subject of extensive exploration efforts in Southeast Asia (for example, the Gunung Putih carbonate complex, East Java Sea, and the Zhujiang and Liuhua platforms, Pearl River Mouth Basin). However, few outcrop equivalents of these early Miocene platforms have been published to date. In this study, we present an outcrop that is an excellent analog for this petroleum province.
The Pirinç outcrop is an early Miocene carbonate platform-to-basin transition exposed on the northern flank of the Mut Basin in southern Turkey. The carbonates were deposited during a time of relative tectonic quiescence in the early Miocene (Burdigalian) over a relict paleotopography inherited from Oligocene tectonic activity. The interval described here is interpreted to be influenced by three large, relative sea level cycles with 100–150-m amplitude. These generated a steep-edged platform with prograding slope and margin geometries during the highstands, whereas during the lowstands, thin carbonate platforms developed with onlapping geometries against the older underlying slump deposits. Stratigraphic relationships indicate that collapse of the platform margin occurred during late highstand to early lowstand times and was coincident with major sea level falls. During transgression, an isolated platform complex developed. Carbonate production on these platforms shut down around the maximum flooding, leading to terminal drowning. This may have been the result of eutrophication caused by the arrival of nutrients from an encroaching deltaiç system, combined with a period of rapid relative sea level rise.
The subsurface Zhujiang Platform (Pearl River Mouth Basin, China) is an early Miocene carbonate platform that developed along the flank of a basement high in the basin. A steep, prograding, carbonate-shelf margin developed with large-scale slumping and collapse features in places. Pinnacles and small isolated platforms grow across a zone seaward of the margin. A strikingly similar stratigraphic organization (steep shelf margin, slumps, and isolated platforms) is observed in the Pirinç outcrop. These similarities are attributed to a common tectonostratigraphic setting (the rapid marine flooding of a complex relict topography during a time of relative tectonic inactivity) and a Burdigalian eustatic sea level curve with cycles of sufficiently large amplitude to have a significant impact on the platform morphology.
At the exploration scale, the outcrop allows us to test three play concepts. From outcrop observations, the slump packets (play concept 1) do not seem to be sufficiently interconnected to make a viable prospect. The development of an enhanced porosity wedge (play concept 2) at the shelf margin will be testable with future outcrop studies. In addition, with future outcrop work, a predictive model for the development of porosity in the isolated platforms can be developed (play concept 3) to more successfully predict porosity prior to drilling. At the reservoir scale, observations of subseismic bedding patterns from the outcrop will help us construct more accurate reservoir models. Additionally, outcrop observations of the dimensions of facies belts and their lateral and vertical variability will improve the way in which we populate a reservoir model with facies and reproduce variability on a scale finer than the interwell spacing.
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Building robust 3-D reservoir models is a major challenge that requires incorporation of geologically defined input parameters. This publication provides an overview of current approaches used in the development of geologically constrained and integrated reservoir models. Each of the 18 papers addresses various stages in the process of creating a reservoir model through the development and incorporation of an analog, extracting the quantitative input parameters on lateral and vertical variability, and the development and modification of a 3-D reservoir model based upon geologically constrained data. This applied volume is divided into two sections. The first is a set of papers illustrating the value and methodology of acquiring geometrical data on the lateral and vertical distribution of reservoir facies, within a sequence stratigraphic framework, using both outcrop analogs and detailed study of modern depositional systems. The second section includes both case studies where outcrop and modern analog data have been incorporated into subsurface reservoir models, as well as papers that illustrate recent advances in simulation and geostatistical methodologies. Together, the two sections provide a comprehensive look at integrated reservoir modeling.