Flow Units from Integrated WFT and NMR Data
Reliable and continuous permeability profiles are vital as both hard and soft data required for delineating reservoir architecture. These profiles can improve the vertical resolution of seismic data, well-to-well stratigraphic correlations, and kriging between the well locations. In conditional simulations, permeability profiles are imposed as the conditioning data. Variograms, covariance functions, and other geostatistical indicators are more reliable when based on good-quality permeability data.
Nuclear magnetic resonance (NMR) logging and wireline formation tests (WFTs) separately generate a wealth of information, and their synthesis extends the value of this information further by providing continuous and accurate permeability profiles without increasing the cost. NMR and WFT data present a unique combination because WFTs provide discrete, in situ permeability based on fluid flow, and NMR responds to the fluids in the pore space and yields effective porosity, pore-size distribution, bound and moveable fluid saturations, and permeability. The NMR permeability is derived from the T2 distribution data. Several equations have been proposed to transform T2 data to permeability. Regardless of the transform model used, the NMR-derived permeabilities depend on interpretation parameters that may be rock specific.
The objective of this study is to integrate WFT permeabilities with NMR- derived, T2 distribution-based permeabilities and thereby arrive at core-quality, continuously measured permeability profiles. We outlined the procedures to integrate NMR and WFT data and applied the procedure to a field case. Finally, this study advocates the use of hydraulic unit concepts to extend the WFT- NMR-derived, core-quality permeabilities to uncored intervals or uncored wells.