ABSTRACT 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.

Abstract The Cusiana field, a giant oil field in the Llanos foothills of Colombia, comprises three sandstone reservoirs: Eocene Mirador, Paleocene Barco, and Cretaceous Guadalupe. Al l contain light, compositionally variable oil with associated gas. Discovered in 1992, the Cusiana field was sanctioned for fast-track development in 1993 and, despite the security problems of the country, was successfully brought onto production in 1995, when the 1.2-bcfd gas reinjection facility started up. Peak production of 310 million BOPD was achieved in 1998. Later, 400 million bbl of production, 72 wells, and a 3-D seismic survey have yielded surprises, experience, and learning relevant to complex development projects elsewhere. Initially, poor reservoir communication and early water and gas breakthrough into producers were considered serious risks. Detailed sedimentologic descriptions were made, and a long-term test, coupled with aggressive static and dynamic pressure monitoring, was initiated. Since described by Cazier et al. (1995) , production experience has shown that a simpler reservoir description resulting from the integration of high-resolution biostratigraphy, sedimentology, geochemistry, and fracture studies with pressure and tracer data has been more successful in describing fluid movement than the earlier sedimentologic-based descriptions and has greatly simplified the task of modeling the dynamic reservoir behavior. The structural complexity revealed by well and 3-D seismic data is greater than original interpretations, resulting in a better quality, original oil-in-place estimate associated with a complex frontal imbricate and multiple oil-water contacts. Among the lessons learned to date is that long-term testing is very useful for demonstrating fieldwide connectivity, but it can lead to difficulty in unequivocal identification of original oil-water contacts. The greatest development challenges are not necessarily those originally predicted during the appraisal phase, so a balanced technical program is likely to be more successful than one focused at perceived, but not necessarily critical, issues.