AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin

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Empirical Evaluation of stratigraphic control on production in clastic reservoirs of the Norwegian continental shelf

Abstract

Inherent reservoirs properties are dependent on reservoir genesis or depositional processes, these properties are modified overtime, hence limited understanding of the geology of a hydrocarbon reservoir is a great deficit in recovery efficiency, adequate knowledge of reservoir architecture is key in placement of injector wells, pressure maintenance and secondary recovery and in turn contribute to reserve growths. The main objection of this study is to determine the impact of depositional environment and the primary facies architecture on reservoir performance. All of the major reservoir intervals in the key fields on the Norwegian continental shelf have been classified within the SAFARI data standard. SAFARI uses a systematic hierarchical schema to describe depositional environments, basin types, paleoclimate architectural elements. Parameters such as recovery factor, maximum oil well rate, depletion rate and other 40 variables were recorded and a unique database was built of all the reservoirs classified into nine depositional sub-environment. All these parameters were analysed using multivariate statistics in order to find out the relative importance of these parameters Stratigraphically dependent variables porosity, permeability, depth were found to control performance of the reservoir, parameters such as reservoir volume, well density, net to gross, temperature and trap type/geometry contribute less to reservoir recovery. Reservoir performance varies for the three gross depositional environments, deep marine have better performance followed by paralic/shallow marine then continental. Similarly performance varies across the nine (9) depositional sub-environments, detailed evaluation of architectural elements of the reservoirs showed intra reservoir sedimentological heterogeneities exists in reservoirs with low recovery. Maximum well rate however is better continental reservoirs compared to deep marine and paralic/shallow marine which is inconsistent with recovery making it very difficult for huge discovered oil to be extracted.