Fluvial architecture of the Burro Canyon Formation using unmanned aerial vehicle-based photogrammetry and outcrop-based modeling: Implications for reservoir performance, Escalante Canyon, southwestern Piceance Basin, Colorado

The Cretaceous Burro Canyon Formation in the southern Piceance Basin, Colorado, represents low sinuosity to sinuous braided fluvial deposits that consist of amalgamated channel complexes, amalgamated and isolated fluvial-bar channel fills, and floodplain deposits. Lithofacies primarily include granule-cobble conglomerates, conglomeratic sandstones, cross-stratified sandstones, upward-fining sandstones, and gray-green mudstones. To assess the effects of variable sandstone-body geometry and internal lithofacies and petrophysical heterogeneity on reservoir performance, conventional field methods are combined with unmanned aerial vehicle-based photogrammetry to create representative outcrop-based reservoir models. Outcrop reservoir models and fluid-flow simulations compare three reservoir scenarios of the Burro Canyon Formation based on stratigraphic variability, sandstone-body geometry, and lithofacies heterogeneity. Simulation results indicate that lithofacies variability can account for an almost 50% variation in breakthrough time (BTT). Internal channel-bounding surfaces reduce the BTT by 2%, volumetric sweep efficiency by 8%, and recovery efficiency by 10%. Three lateral grid resolutions and two permeability-upscaling methods for each reservoir scenario are explored in fluid-flow simulations to investigate how upscaling impacts reservoir performance. Our results indicate that coarsely resolved grids experience delayed breakthrough by as much as 40% and greater volumetric sweep efficiency by an average of 10%. Permeability models that are upscaled using a geometric mean preserve slightly higher values than those using a harmonic mean. For upscaling based on a geometric mean, BTTs are delayed by an average of 17% and the volumetric sweep efficiency is reduced by as much as 10%. Results of the study highlight the importance of properly incorporating stratigraphic details into 3D reservoir models and preserving those details through proper upscaling methods.

GEOMETRI PERLAPISAN BATUPASIR KONGLOMERATAN SEBAGAI SISIPAN PADA FORMASI NANGGULAN DI KALI WATUPURU DAN KALI SONGGO, PEGUNUNGAN KULON PROGO, YOGYAKARTA

Nanggulan Conglomeratic Sandstone is one of important part of Nanggulan Formation which is deposited during Middle Eocene to early Late Eocene (Saputra & Akmaluddin, 2015) or Late Oligocene (Rahardjo, 1995). The grain composition of Nanggulan conglomeratic sandstone is characterized by various rock fragments (metamorphic, igneous, sedimentary rocks) which mixture up to fine to coarse sand-sized matrix. Other materials present within the Nanggulan conglomerathic sandstone are shell fragments, coal remains, siderithic concretions which is deposited within high energy condition. Geometry of conglomeratic sandstone stratification is still being a question among the researchers due to discontinuous sand body character. To study external form of sandstone body needs to combine with internal characters such are grain texture, grain or fragment composition, sedimentary structures to predict a depositional facies. This research is dedicated to study the character of the Nanggulan conglomeratic sand body. Field geological observation was conduct to two rivers i.e Kali Watupuru and Kali Songgo where transecting the Nanggulan beds. The grain or fragments concentration of Nanggulan conglomeratic sandstone displays in various condition for example lying above an erosional surface to the bottom position, or concentrate to the upper layer. It also appears to be engaged in coarser size matrix, or displays a dense grain composition to elsewhere. Geometry of the Nanggulan conglomeratic sandstone represents a lens geometry which pinching-out to the edge of body. However, to the top of lens geometry were found steep joints cross cutting the sand layers. Initial geometry of Nanggulan conglomeratic sandstone indicates a channel fill shape due to filling sediments into the erosional feature of underlying beds. When lithification and compaction process occurred along the burial and uplifting tectonic phase, a channel fill geometry becomes lens geometry. Bulging to the centre part and thinning to the edge of sandstone body, is caused by differential compaction process. Lens geometry is believed as one example of structural trap model for sandstone reservoir. The occurrences of vertical joints to the Nanggulan conglomeratic sandstone need to be considered as seal potential within clossure trap or even more causing hydrocarbon leakings. If development of vertical joint occurs along migration process, it may be potentially leak. However, if joints already sealed parts of hydrocarbon pool may create a compartmentalization reservoir body. By doing this investigation could predict an advance reservoir modelling study using outcropp analogues. Keyword: Nanggulan conglomeratic sandstone, lens geometry, sandstone body.

Sedimentation of deep-water turbidites in the SW part of the Pannonian Basin

Sedimentation of deep-water turbidites in the SW part of the Pannonian BasinThe Sava Depression and the Bjelovar Subdepression belong to the SW margin of the Pannonian Basin System, which was part of the Central Paratethys during the Pannonian period. Upper Pannonian deposits of the Ivanic-Grad Formation in the Sava Depression include several lithostratigraphic members such as Iva and Okoli Sandstone Member or their lateral equivalents, the Zagreb Member and Lipovac Marlstone Member. Their total thickness in the deepest part of the Sava Depression reaches up to 800 meters, while it is 100-200 meters in the margins of the depression. Deposits in the depression are composed of 4 facies. In the period of turbiditic activities these facies are primarily sedimented as different sandstone bodies. In the Bjelovar Subdepression, two lithostratigraphic members (lateral equivalent) were analysed, the Zagreb Member and Okoli Sandstone Member. The thickness of the Bjelovar Subdepression ranges from 50 meters along the S and SE margins to more than 350 meters along the E margin. Generally, detritus in the north-west part of the analysed area originated from a single source, the Eastern Alps, as demonstrated by sedimentological and physical properties, the geometry of the sandstone body and the fossil content. This clastic material was found to be dispersed throughout the elongated and relatively narrow Sava Depression and in the smaller Bjelovar Subdepression. Sedimentation primarily occurred in up to 200 meters water depth and was strongly influenced by the sub-aqueous paleorelief, which determined the direction of the flow of turbidity currents and sandstone body geometries. The main stream with medium- and fine-grained material was separated by two independent turbiditic flows from N-NW to the SE-E. Variability in the thickness of sandstone bodies is the result of differences in subsidence and cycles of progradation and retrogradation of turbidite fans.