The purpose of the study was to quantify and evaluate the impact of geological heterogeneities on connectivity in channelized turbidite reservoirs. The main technical objectives of the project were: the identification of the architectural elements of the deep-water system under analysis, the development of different geological models, the quantification of reservoir heterogeneity and the evaluation of reservoir connectivity and the outline of an early appraisal strategy.
An integrated approach was applied, using different frameworks, to two eni's deep-water assets: the first, an exploration asset in the Mediterranean, and the second, a West African field in development. This methodology was based on an earth models construction phase (reservoir characterization and reservoir modeling) and on a dynamic simulations phase (streamline simulations and well test simulations).
Reservoir characterization was performed by interpreting 3D seismic data using a high precision 3D seismic interpretation software. Key surfaces were interpreted in the reservoir interval. Furthermore, deep-water elements and architectures, mainly stacked channels and distal lobes, were duly identified through the interpretation of seismic sections and amplitude maps.
Reservoir modeling consisted of Object-Based and Multi-Point Facies Simulation (MPFS) approaches. A sensitivity analysis was carried out to define critical parameters and their ranges in order to fully capture geological uncertainties and realize different static models. The selected parameters were: seismic conditioning in the MPFS (amalgamation), facies volume fraction, channels shape and shale drapes content.
To quantify heterogeneity and analyze connectivity, streamline simulations were carried out using a Streamline Simulator. For each geological model, a Dynamic Lorenz plot (storage capacity vs. flow capacity) and its related coefficient (standard measure of heterogeneity) were determined using an in house code. It resulted that all the selected parameters, except channels shape, impacted considerably on connectivity.
To outline an early appraisal strategy, well test simulations were performed using an hypothetical exploration well and a standard Dynamic Simulator. Well test simulation was found to be an interesting qualitative tool to identify heterogeneities, especially shale drapes content, and condition further appraisal decisions.
Considering the promising results, this approach will be further developed to effectively reduce the range of uncertainties, mitigate the associated risks and guide appraisal strategies in future deep-water prospects.