--> Abstract: Digital Rock Physics Study of Organic-Rich Facies in Mississippian Gas Shale, by Florez, Juan-Mauricio; Walls, Joel; and DeVito, Juliana; #90166 (2013)
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Digital Rock Physics Study of Organic-Rich Facies in Mississippian Gas Shale

Florez, Juan-Mauricio1; Walls, Joel; and DeVito, Juliana
1[email protected]

This study of organic-rich shale, based on three wells with significant contrast in performance, shows that well productivity in gas shale resources can be related to mineralogical composition and elastic properties. This digital rock physics analysis was carried out on shale samples selected using log and core data from wells with different thermal maturity, burial depth, petrophysical properties and gas productivity. The results show that the more productive well has more silica-rich organic facies with a higher proportion of porous organic matter (POM), while the less productive well has more clay-rich organic facies with a lower proportion of POM.

The proportion of POM can be related to silica content, compaction, and/or thermal maturity. Micro-scale digital images show important differences in the fabric of silica-rich and clay-rich organic shales. Digital images of silica-rich organic facies locally show a delicate fabric of randomly oriented clay platelets associated with abundant POM. In contrast, clay-rich organic facies have a more laminated fabric with aligned clay platelets and a lower proportion of POM. Our data also suggest that compaction and thermal maturity play a role on preservation of POM. The well with deeper maximum burial depth shows slightly higher values of vitrinite reflectance indicating higher thermal maturity. This deeper well has similar proportions of organic matter (TOC) with lower porosity (less POM) and a strongly oriented fabric indicative of a higher degree of compaction. All together, our observations indicate that POM is more abundant in silica-rich organic facies, and that preservation of POM can be affected by maximum burial depth and kerogen thermal maturity.

Porosity, TOC and permeability have been determined from computational rock physics and compared to laboratory measurements. They show good agreement with TOC laboratory data, although lower porosities. A porosity-permeability relationship has been obtained and compared to laboratory measurements, showing good agreement for porosities above 4% and lower permeabilities for porosities below 4%. However, the digital porosity-permeability trend agrees with published trends from laboratory measurements on other data sets. Finally, log data analysis of the elastic properties of different shale types illustrates that brittleness and Previous HitincompressibilityTop can be combined to identify the most productive facies in this Mississippian Gas Shale resource.

 

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013