Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Carbonate Rock Typing – Modelling Heterogeneity. A Case Study Comparison of Whole Core and Core Plug Permeability Data
(1) Shell International, Rijswijk, Netherlands.
Reservoir characterization and modeling studies are faced with the challenge of populating reservoir models with representative values of permeability and distributing the values in 3D space such that accurate flow simulation is achieved. The challenge is particularly great in carbonate reservoirs where the spatial distribution of permeability is complicated by different pore types and rock fabric heterogeneities that span a range of scales. A companion paper addresses how to better characterize pore to plug-scale (micron to cm scale) heterogeneity leading to improved prediction of porosity-permeability correlations. This paper addresses permeability heterogeneity at the cm to dm scale as illustrated by a case study comparing core plug and whole core permeability data. Insights into this upscaling step provide insights into permeability upscaling and averaging in general.
Two cored intervals, each tens of meters in length, within the same reservoir have significantly different heterogeneity characteristics as illustrated by the variability in permeability through the (vertical) cored sections and by corresponding differences between plug and whole-core measured permeability. One cored section has relatively homogeneous plug permeability values and the whole core data indicates a factor 2 to 3 increase in permeability compared to plug data. The second cored section, with much greater heterogeneity, has whole core permeability data that is a factor 8 higher on average than the plug data. The heterogeneity differences can be related to different depositional and diagenetic fabrics that affect pore connectivity at scales larger than plug scale. This highlights the necessity to recognize those depositional and diagenetic processes that control pore connectivity across a range of scales in order to accurately model effective permeability for flow simulation. The identified heterogeneities are a likely reason why well-test based permeability values are higher in the heterogeneous section than would be inferred from routine plug data.