Abstract:

This paper reports data from observation of 55 wells and identification of more than 200 casting thin sections, mercury
injection data analysis and logging interpretation of 92 wells and analyzed physical properties differences between the Silurian-
Carboniferous clasolite reservoirs and the Ordovician carbonate reservoirs in the Tazhong area. Key controlling factors for the physical
properties differences were discussed based on geological setting. The results showed that the clasolite reservoirs have medium-low
porosity and medium-low permeability, and the carbonate reservoirs have lowto ultra-low porosity and lowto ultra-low permeability. The
correlations among porosity, permeability and pore-throat radius are totally different for the two different types of reservoirs. The
physical properties differences were controlled by sedimentation, which embodies sedimentary facies difference from macroscopic view

and minerals composition difference and grain size from microscopic perspective. Besides sedimentation, physical properties
differences are mainly controlled by compaction, dissolution, cementation and fracture rebuilding effect. Compared with the variation of
physical properties of clasolite reservoirs, the carbonate reservoirs are more likely affected by dissolution, cementation and fracture
rebuilding effect, and are more difficultly affected by compaction. Comparative studies of key controlling factors of the physical
properties show that clasolite reservoirs should focus on primary pore for petroleum exploration, while carbonate reservoir should on
secondary pore.

Key words: reservoir physical properties, key factor analysis, clasolite reservoirs, carbonate reservoir, Tazhong area