Reducing Uncertainties in Frontier or Underexplored Carbonate Plays by Integrating Palaeogeographic Mapping, Palaeo-Earth System Models and Numerical Stratigraphic Forward Modelling

Abstract

In frontier or underexplored plays and fields, where available data is limited, quantified geological parameters such as sediment thickness and facies distribution are often poorly constrained. In order to facilitate prediction of sedimentary patterns we have developed a new workflow integrating palaeogeographic mapping, palaeo-Earth system models (PESM) outputs and numerical stratigraphic forward models (SFM). The focus of this talk will be on the application of this workflow to the Aptian Shuaiba formation in the Rub al Khali basin, Middle East. Whilst the Shuaiba formation is not a frontier play, it was selected for this research because the formation has been extensively studied and has a large volume of data available in the public domain, we can therefore better asses the modelled results and the suitability of the workflow. For this workflow, we utilised global data-constrained palaeogeographic maps, constructed on base maps using CGG Plate Kinematics deformable plate model, to underpin global palaeo-digital elevation models (DEM) and define palaeo-drainage. DEM were coupled with PESM (UK Met Office HadCM3 GCM) and palaeotidal models (Imperial College, UK, ICOM) to provide quantitative global, palaeoclimatic and palaeooceanographic data. Key outputs from the palaeogeographic mapping and PESM include sea surface temperature, sea surface salinity, oceanic currents, tidal range, tidal bedstress and wave energy, which were considered as the most important controls on the distribution of carbonate facies on the shelf. In order to accurately model the sedimentary thickness and stratal geometries, numerical SFM were utilised to produce deterministic models that replicate and predict the spatial distribution of stratal geometries, sedimentary thickness and lithologies according to pre-defined input parameters and boundary conditions. By integrating SFM with the parameters defined by PESM, it is possible to convert 2D palaeogeographic maps into 3D palaeodepositional models. We aimed to use these models to better understand the presence and character of reservoir facies. By using SFM, we are able to analyse the behaviour of sedimentary systems extracted from palaeogeographic maps and evaluate their behaviour and distribution in the context of palaeoclimatic and palaeoceanographic data. We applied the new methodology in the Rub Al Khali basin in the Middle East to assess the accuracy and the predictability of facies distribution in the Shuaiba formation. The results showed a good match between 2D-palaeogeography maps produced via different modelling techniques, the maps exhibited similarities in the distribution of deposits. The data from the SFM has an added advantage in that it contains information that can be used to improve our facies maps and understanding in the 3D-domain. SFM techniques also allowed us to test some of the key controls on facies distribution (e.g. subsidence rate). The workflow marks an important step in characterisation of carbonates in the region, we hope to use it in the future to better-characterise reservoirs at exploration stage, where limited well data is available.

AAPG Datapages/Search and Discovery Article #90370 ©2020 AAPG Middle East Region Geoscience Technology Workshop, 3rd Edition Carbonate Reservoirs of the Middle East, Abu Dhabi, UAE, January 28-29, 2020