Thin Bed Analysis with NMR Logs
J.C. Glorioso, V.H. Goitia, R. Arnez and H. Serrano
Event name: 77th EAGE Conference and Exhibition 2015
Session: Petrophysics II
Publication date: 01 June 2015
Info: Extended abstract, PDF ( 1.74Mb )
Price: € 20
Laminated reservoir involving thin beds of shale and sandstone are elusive for petrophysical formation evaluation and the parameters necessary to estimate hydrocarbons in-place in such reservoirs are difficult to obtain using standard well logs. Alternative methods based in NMR logging stand-alone measurements can bring a different approach and may complement or even replace other frequently used methods. NMR analysis is going to be based in terms of bulk rock volume provided that NMR logs do not have resolution enough to solve thin sand and shale lamina properties. Outcomes from NMR logs like free-fluid, capillary-bound fluid, and clay-bound fluid are related to (bulk rock) total, effective, and free fluid porosity when expressed in terms of porosity partitioning. A relationship can be established in terms of pore size to derive clay, silt and sand indexes using the same porosity partitioning.In terms of water saturation, NMR logs theory indicate that a relationship of free fluid porosity exists with total and effective porosity in that the ratio of free-fluid porosity with those last two may well represent total and effective irreducible water saturation of the rock. Therefore, this method can be applied in the hydrocarbon leg to assess the water saturation of the reservoir.