Implication of Depositional Architecture and its Control on Vertical and Lateral Variation of Reservoir Facies — A Case Study from North Kuwait Field

Mishra, Prasanta K.; Al-Kanderi, Jassim M.

An attempt has been made to illustrate the depositional architecture of the Neogene sequence and layer characteristics of the reservoir and non-reservoir rocks from a North Kuwait field.

The Neogene sequence in the study area can be rationalised into 6 largely fluvio-deltaic depositional facies, essentially ranging from proximal fluvial channel-fill sandbodies and floodplain mudrocks to distal, marine-influenced deltaic deposits including distributary channelfills, mouthbars, interdistributary bays/lagoons as well as shallow marine lower shoreface and offshore facies associations. The latter are associated with distinct transgressive events that episodically have transformed the fluvio-deltaic complex into a shoreface-type depositional environment. It is postulated that, at least, parts of the delta system were influenced by estuarine conditions, although the full extent of this cannot be assessed by the available dataset.

Field-wide correlatable flooding, transgressive and erosion surfaces (sequence boundaries) are present in this formation and provide the sequence stratigraphic framework for the interpretation of the succession's depositional evolution and zonation. The gross vertical organisation of the sediments , together with field-wide correlations, suggest that the depositional heterogeneity increases from the base to the top of the succession; this is highlighted by a higher proportion of interbedded mud-prone fluvial/deltaic and marine influenced deposits up-hole.

The main reservoir sandbodies are fluvial and rarer distributary channel-fills, which commonly have multistorey/multilateral depositional architectures. While the majority of the clean fluvial/distributary sandbodies have up to excellent reservoir qualities, poorer qualities are generally associated with more argillaceous channel-fill sandstones.

Although they occur in various proportions within individual layers, mapping of the argillaceous channel-fills shows that they tend to be more commonly distributed in the upper parts/towards the top of the sandstone-dominated part and towards the marginal areas of the Field, notably to the South/Southeast and North. The vertical and lateral facies distribution, together with biofacies trends, are detailed for each layer in this study and are also illustrated on layer-specific facies maps.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013