Abstract This paper represents the second part of an integrated study that is focussed on the development and distribution of reservoir bodies and properties in epeiric carbonate systems. It is based on outcrop analogue data from Triassic ‘layer-cake’ carbonates in the South German Basin, which were deposited along an epicontinental, very gently inclined carbonate ramp. The reservoir facies consists of skeletal and oolitic carbonate grainstones (Φ max 23%, K max 700 mD), which are organized in a pronounced hierarchy of stratigraphic cycles. Based on outcrops, cores, gamma ray (GR) logs and thin sections, a high-resolution, geocellular 3D facies model was generated, which covers the area of a Middle East giant gas field (25×36 km). The spatial distribution of reservoir properties was systematically investigated on different scales. The lateral distribution of reservoir properties remains in the same order of magnitude for hundreds of metres, within in the same stratigraphic position. However, on a kilometre scale, facies bodies, diagenetic trends and thus reservoir properties show gradual lateral changes. Vertically, in contrast, properties change commonly on a decimetre scale and are largely controlled by stratigraphic cycles. Petrophysical modelling enhanced the understanding of key factors and processes controlling both reservoir quality and quantity.

Abstract This study presents a workflow for 3D modelling of carbonate reservoirs using multiple-point statistics (MPS) in the framework of a pre-existing model. It consists of the following steps: (1) applying a hierarchical classification scheme for carbonate geobodies; (2) based on this classification, retrieval of relevant data from Carbdb, a novel software to manage a database of analogue studies; (3) construction of training images based on the retrieved data from Carbdb; and (4) using the training images when building a 3D reservoir model with MPS. MPS makes use of training images to capture depositional patterns, which will then be reproduced during the stochastic simulations. Carbdb provides a library of quantitative data such as dimensions, geometries and the distribution pattern of geobody analogues necessary for building training images. The MPS workflow was applied to carbonate shoal bodies from a reservoir analogue, the Muschelkalk in SW Germany. Present-day shoal bodies from the Arabian Gulf were retrieved from Carbdb as possible modern analogues to generate training images. The realizations of this MPS approach are compared with a previously established 3D geocellular model that was built deterministically by interactive facies modelling. The MPS simulations produced geologically more realistic facies distributions with higher facies heterogeneity, similar to the depositional patterns observed in modern analogues.

Abstract The sequence stratigraphic methodology can be readily applied to the cratonic basin-fill of the German Triassic System, which consists of shallow-marine to terrestrial mixed carbonate/siliciclastic rocks. The whole Triassic succession represents a second-order transgression/regression cycle, in which the continental redbeds of the Buntsandstein pass gradually upwards into Muschelkalk carbonates and evaporites and back into continental Keuper redbeds. Peak transgression occurred during the Late Muschelkalk (Ladinian). The Triassic cycle is built by at least 13 3rd-order depositional sequences, consisting of systems tracts and parasequences. Many bounding surfaces represent widely used marker beds, long used in classical lithostratigraphy. Using a synthesis of outcrop and well-log data on stratal geometry, facies, cycle stacking patterns and paleogeography, a regional coastal onlap chart was constructed. Within the limitations of the presently available biostratigraphic data, the observed cycles appear to correlate fairly well to those in other areas, but include a number of additional sequences not included in the Haq et al. (1987) chart. Comparative analysis of regional onlap curves from different, globally separate Triassic basins, together with an improved biostratigraphy, will be necessary to relate the accommodation changes to eustatic versus tectonic controls and to produce a refined eustatic chart. The German Basin could provide a favorable calibration point for such an analysis.