--> --> Integration of the Effects of Bioturbation on Reservoir Quality Into Reservoir Modeling of CREEK Field, Niger Delta Petroleum Province

2018 AAPG International Conference and Exhibition

Datapages, Inc.Print this page

Integration of the Effects of Bioturbation on Reservoir Quality Into Reservoir Modeling of CREEK Field, Niger Delta Petroleum Province

Abstract

A comparative study of five wells from five fields in both the Central Swamp and Coastal Swamp depobelts of the Niger Delta was carried out to investigate the variation in the abundance and diversity of ichnofossils, with the aim of assessing the intensity of bioturbation and their corresponding impact on reservoir quality and hydrocarbon volume. The work focused on the integration of ichnology, sedimentology and sequence stratigraphy. The workflow included detailed sedimentological description of cores and collation into lithofacies, lithofacies association and depositional environments as well as ichnological studies. The ichnological studies concentrated on grouping of trace fossils identified into ichnofacies viz: Skolithos, Cruziana and Zoophycos; interpretation of depositional environments and reservoir characterization. The intensity of bioturbation expressed as a ‘Coefficient of bioturbation (Cb)’ was also quantified. Core gamma alongside core plug porosity and permeability displayed using the WellCAD software was integrated with wireline logs, biostratigraphic and seismic data using the PETREL software. Sequence stratigraphic and reservoir correlation were done while the facies, porosity and permeability obtained were upscaled into a 3D static model. Results showed that clean sandstones of the upper shoreface and tidal channels have very good to excellent porosity and permeability when not bioturbated. However, in these environments, the effect of intense bioturbation (by Ophiomorpha and Asterosoma) tended to reduce the reservoir quality appreciably. In the heterolithic lithofacies of the distal middle and lower shoreface deposits and upper sections of tidal channels, intensely bioturbated horizons (muddy sandstone facies with clean sand-filled burrows, e.g. Thalassinoides and Planolites) were found to possess higher poroperm than sparsely burrowed intervals. This work revealed that bioturbation can either reduce or increase permeability and porosity. Petrophysical characteristics of the reservoir lithofacies are highly dependent on trace fossil morphology, presence or absence of burrow linings, burrow size, nature of burrow fills and bioturbation intensity in different environments of deposition. Hence, the integration of the effects of bioturbation on poroperm into static model (i.e. the concept of bioturbation modelling) as an improvement in reservoir modelling with the view to close uncertainty gaps in reserve estimation is imperative.