The Impact of Static Modeling Parameters from Flow Response: Large Scale Steamflood Pilot (Lsp) Area, Wafra First Eocene Reservoir, Partitioned Neutral Zone (PNZ)
The First Eocene reservoir is a Paleocene/Eocene age dolomite reservoir. It is the shallowest reservoir at Wafra Field. The porosity of the reservoir averages about 35% and permeability averages 100-500 mD (core plugs with greater than 1000 mD are common). The 40-acre LSP project is located in the southern portion of the field and contains 56 new producers, injectors, and temperature observation wells. Routine and special core analyses from four wells cored through the entire productive portion of the reservoir are supplemented by an extensive suite of well logs, image logs, and high resolution 3D seismic data.
The LSP area static models were built using well log and core data with well log derived semivariogram models. The semivariogram models obtained from the pre-LSP project wells have horizontal correlation lengths on the order of 1500-2000 m. These older, primary development wells have a typical spacing of 500 m. Semivariogram models obtained from the new LSP project wells have correlation lengths on the order of 300 m. The average well spacing of the LSP project wells is less than 40 m (well pair separation ranges from 12 m to 100 m).
Reservoir models were built to test the impact of semivariogram parameters on reservoir fluid flow response. Fine scale static models (5 m areal grid size, 4.5 million total cells) were simulated without up-scaling using 3D streamline simulation. Dynamic scenarios selected were designed to reduce the noise of well distance, sweep direction and material balance error on the results. Analysis of the results demonstrate that models built using the shorter semivariogram ranges have higher recovery than models built using large semivariogram range. The results also showed that permeability heterogeneity reduced recovery given the same reservoir connectivity. The conditioning well density does not significantly change recovery given the same reservoir connectivity. The results of this study will be used to guide workflow decisions and data acquisition for the full field modeling of the reservoir.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009