Stochastic Reservoir Model for the First Eocene Reservoir, Wafra Field, Partitioned Neutral Zone (PNZ)

Abstract

The Wafra field is located in the Partitioned Neutral Zone (PNZ) between Saudi Arabia and Kuwait. The field produces from five intervals of which the Tertiary First Eocene dolostone reservoir is the youngest. The reservoir consists of extensively dolomitized peloidal packstones and grainstones that were deposited on a very gently dipping, restricted ramp environment with interbedded evaporites. Discovered in 1954, the First Eocene reservoir has produced more than 280 MMbbls of 17-19° API, high sulfur oil. The stochastic reservoir model utilizes a new sequence stratigraphic framework and is based on data from over 285 wells. The geostatistical model covers a 17.3 x 21.5 km area (372 km 2). Porosity was distributed using sequential Gaussian simulation (SGS) constrained by stratigraphic layer. Porosity semivariogram range parameters average 1500 m (compared to an average well spacing of about 500 m) and show a moderate N120E trend. Permeability was distributed using a cloud transform algorithm that was constrained by core data for specific stratigraphic layers. Water saturation (Sw) was distributed by collocated cokriging with SGS using Sw well log