Petrophysical Analysis of Vuggy Porosity in the Shuaiba Formation of the United Arab Emirates

Surassawadee Tanprasat
MS Graduate Student
Dept. of Geology and Geological Engineering, Colorado School of Mines
Golden, CO
[email protected]

The main objective of this study is to determine the relationship between well logs and porosity and permeability in the highly heterogeneous carbonate reservoir of the Shuaiba Formation in a giant oil field in the United Arab Emirates. Pore-size distribution, log-derived porosity from conventional logs, and permeability data from a cored well, will be used to map flow units and to optimize field production.

The Shuaiba Formation is the most important onshore oil reservoir in the United Arab Emirates, with an estimated 22 billion bbl OOIP and an estimated recovery factor of about 40%. However, it is also the most complicated carbonate reservoir and is characterized by small-scale geological heterogeneity. The depositional environment varies from shallow-shelf to deep-water slope sediments, with four main reservoir facies and 17 Reservoir Rock Types (RRT) that range from non-productive rocks to those with up to 30% porosity and 20-Darcy permeability.

This study will quantify pore-size distribution in a vuggy core (556 ft/169.5 m) using image analysis of core slabs and thin sections. We will compare the observed pore-size distribution with the NMR log - T₂ distribution. Neural network modeling will be used to predict vuggy porosity from conventional open-hole logs in other wells. A flow-unit model, based upon graphical analysis of cumulative Φ-h and k-h plots, will be compared with production log data.

AAPG Search and Discovery Article #90033©2004 AAPG Foundation Grants-in-Aid