Geostatistical Earth modeling of cyclic depositional facies and diagenesis

Abstract

In siliciclastic and carbonate reservoirs, depositional facies are often described as being organized in cyclic successions that are overprinted by diagenesis. Most reservoir modeling workflows are not able to reproduce stochastically such patterns. Herein, a novel geostatistical method is developed to model depositional facies architectures that are rhythmic and cyclic, together with superimposed diagenetic facies. The method uses truncated Pluri-Gaussian random functions constrained by transiograms. Cyclicity is defined as an asymmetric ordering between facies, and its direction is given by a three-dimensional vector, called shift. This method is illustrated on two case studies. Outcrop data of the Triassic Latemar carbonate platform, northern Italy, are used to model shallowing-upward facies cycles in the vertical direction. A satellite image of the modern Bermuda platform interior is used to model facies cycles in the windward-to-leeward lateral direction. As depositional facies architectures are modeled using two Gaussian random functions, a third Gaussian random function is added to model diagenesis. Thereby, depositional and diagenetic facies can exhibit spatial asymmetric relationships. The method is applied in the Latemar carbonate platform that experiences syn-depositional dolomite formation. The method can also incorporate proportion curves to model non-stationary facies proportions. This is illustrated in Cretaceous shallow-marine sandstones and mudstones, Book Cliffs, Utah, for which cyclic facies and diagenetic patterns are constrained by embedded transition probabilities.

Importance of accounting macro heterogeneity of productive strata to improve efficiency of water alternating gas injection process

“…In the framework of the analysis of macro heterogeneities in petrophysics of pay series, the dynamic analysis of wavefield was carried out during interpretation of seismic survey data. One of the results is the forecast mapping of petrophysical parameters based on interpolation of relevant interwell space data with regard to wavefield properties [18,19]. The outcome is the increased reliability of geological models, appraisals of oil and gas reserves and, consequently, quality of reservoir simulation [20].…”

A geocellular modelling workflow for partially dolomitized remobilized carbonates: An example from the Hammam Faraun Fault block, Gulf of Suez, Egypt

“…Reservoir modelling packages have largely been formulated to model siliciclastic reservoirs, and therefore many of the default algorithms are not directly applicable to carbonate systems. Although advances are now being made in carbonate reservoir modelling, these often rely on bespoke geostatistical modelling (e.g., Beucher and Renard, 2016), prior outcrop data in order to constrain models, for example using multipoint statistics (e.g., Janson and Madriz, 2012), specifically consider only one element of the reservoir, such as fractures (e.g., Geiger and Matthai, 2014) or focus on cyclicity rather than discontinuous sedimentary or diagenetic geobodies (e.g., Le Blevec et al, 2020). In particular, there are few published examples of geocellular models that aim to reproduce the spatial distribution and morphology of diagenetic geobodies using commercial software (Pöppelreiter et al, 2008;Gomes et al, 2018).…”