Research on Effectiveness and Application of Fixed-Plane Perforation Fracturing Technology in Ultra-Low-Permeability Reservoir
Table 3
Classification standard of a single sand body oil reserves [8].
Classification
Displacement characteristics
Porosity (%)
Permeability (mD)
Microscopic pore throat radius (μm)
Natural gamma (API)
Class I
Good physical properties, easy to form (fingering) watered-out channels, early watered-out, good displacement effect, and high oil recovery
≥14
≥0.8
≥0.25
0.3-0.5
Class II
The water flooding front advancing is slow, physical properties are relatively poor, swept efficiency is low and widely distributed, and there is high shale content
≥10-14
≥0.2-0.8
≥0.1~0.25
1.5-0.3
Class III
Belonging to the unconventional tight formation, which cannot be swept and used temporarily; the reserves can be calculated, unless developed by gas flooding in the future