A sequence stratigraphic study of the Cenomanian-early Turonian Mishrif Formation has been carried out in the SW of the United Arabian Emirates (UAE) in order to understand the evolution of the reservoir distribution and occurrence of potential stratigraphic and diagenetic traps in the UAE.

The study has used an integrated reservoir approach that includes regional geology, seismic stratigraphy together with well data. The use of the core data and logs has allowed identification of facies changes, key stratigraphic surfaces and a number of a few feet thick dense intervals that show a relatively high lateral correlatibility, which appear to be below the seismic resolution. The use of seismic attributes together with the well calibration has been crucial to define seismic facies and their lateral and vertical distribution.

Results from this study allowed recognition of several smaller scale 3rd order cycles, which are comprised in a larger 2nd order genetic sequence. Each small-scale cycle is bounded by a sequence boundary overlain by a flooding event made up of a thin dense interval which shows an increase in argillaceous content and locally chert. These sequences are characterised by an eastward progradation from muddy inner ramp facies passing upwards to rudist-rich patch reef/mixed skeletal shoal complexes developed in an inner to mid-ramp depositional setting. This latter setting appears to be best developed in the uppermost large-scale sequence, below the regional unconformity that separates the Mishrif from Ruwaydha and Tuwayil formations. Highly porous facies appear to decrease seismic velocity.

The integrated approach presented here captures the variety in depositional environments, architecture, geometry and reservoir heterogeneity, which results in higher likehood to identify stratigraphic and diagenetic traps.

Furthermore, the recognition of seismic characteristics of the Mishrif reservoir may be used as a tool to predict the distribution and evolution of units that create velocity variations in the Mishrif Formation and which affect the structural definition of deeper reservoirs as the Shuaiba Formation.

Keywords:
Upstream Oil & Gas, platform margin, Reservoir Characterization, facies, reservoir quality, lithofacies association, geometry, evolution, interpretation, depositional environment
Subjects:
Reservoir Characterization, Exploration, development, structural geology, Seismic processing and interpretation
Copyright 2017, Society of Petroleum Engineers
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