Tidal versus fluvial point bars: Key features from the integration of outcrop, core and wireline log information of Triassic examples

Abstract

The Triassic red beds of the Tabular Cover of the Iberian Meseta are an excellent reservoir outcrop analogue, a direct consequence of high-quality exposures, which offer exceptional three-dimensional outcrops, as well as a wide variability of depositional environments. Fluvial and transitional with tide-influenced and wave-influenced settings are recognised. Three point bar geobodies of similar scale, but influenced by different processes, were selected from this succession. Point bar geobody 1 was influenced by purely fluvial processes while geobodies 2 and 3 were tide-influenced. Both types of geobody were developed as point bar deposits in sinuous channels. A fully integrated study was carried out on these geobodies, utilising both outcrop and subsurface-based approaches, to characterise the key differences between fluvial and tidal point bars in the sedimentary record. The outcrop-based component involved traditional field data collection methods alongside digital techniques and data capture, including the use of digital outcrop models. Additionally, subsurface-based methods were employed, utilising core and wireline logs obtained from wells drilled in close proximity to the outcrop. The integration of these approaches aims to accurately differentiate the depositional settings of the three different geobodies, which while apparently very similar in many key respects also exhibit considerable differences when considered from the perspective of subsurface management of potentially similar geobodies. This study also emphasises the need to clearly distinguish high-sinuosity deposits based on their depositional sub-environment in order to properly evaluate their potential for subsurface management. Additionally, it highlights the presence and importance of internal baffles that may well influence fluid migration and indeed even compartmentalise geobodies. Three point bar geobodies of similar scale, but influenced by different processes, have been selected in this succession. A fully integrated study was carried out on these geobodies, utilising both outcrop-based and subsurface-based approaches, to characterise the key differences between fluvial and tidal point bars in the sedimentary record.