--> Application of NMR Technology to Carbonate Reservoirs: Relating Best Flow Characteristics of Depositional, Diagenetic, and Hybrid Pore Types to Their Host Rock, Adams, Aaron J.; Ahr, Wayne M., #90100 (2009)

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Application of NMR Technology to Carbonate Reservoirs: Relating Best Flow Characteristics of Depositional, Diagenetic, and Hybrid Pore Types to Their Host Rock


Adams, Aaron J.1
 Ahr, Wayne M.2


1
Anadarko Petroleum Corp, The Woodlands, TX.
2
Geology & Geophysics, Texas A&M University, College Station, TX.


Carbonate reservoirs are a network of pores and connecting pore-throats that contain at least half of the world’s oil. Genetic classification of carbonate pores enables one to map the pore types that have greatest influence on reservoir performance. Though NMR logging has been used to estimate pore sizes, it has not been used to identify genetic pore types or to aid in determinations of reservoir quality for different pore assemblages.

Five genetic pore types were identified in 40 carbonate and 7 sandstone samples from the Alabama Gulf Coast, Texas panhandle, and Australian shelf. Sample lithologies include a variety of pore types found in ooid and skeletal grainstones, dolomitized microbialite reefs, and quartz arenites. Results demonstrate close correspondence between NMR-derived pore volumes and 2-D pore size and shape gleaned from petrographic image analysis. Comparisons of real and synthetic pore shapes showed that shapes of all pore types in the medium size range of 0.02-0.5mm can be reliably compared with synthetic varieties, but such comparisons were unreliable for vuggy pores smaller than 0.5mm. T2 relaxation curves revealed distinct amplitude and wavelength patterns between the various genetic pore types. NMR-derived pore volumes on pores with ferroan dolomite interiors underestimated pore diameter by up to 3 orders of magnitude. Calculated pore-throat sizes from MICP data correlate strongly with measured permeability.

Samples with high, intermediate, or low poroperm values exhibited characteristic T2 curves confirming that reservoir quality can be estimated from NMR measurements, even in carbonates. This new approach will improve flow unit mapping, advance the understanding of compartmentalized targets, and accordingly lower the risk in overall field development.

 

AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil