Environmental Engineering Reference
In-Depth Information
Figure 5 Bakken Shale Formation stratigraphic column, illustrating the 'hybrid'
shale oil reservoir concept.
achieved by drilling and completing lateral wells in sections where the
interbedded units are best developed.
3 What Makes a Shale Reservoir?
Several key geological criteria have been developed from the experience
gained from exploration for shale plays and their subsequent exploitation:
Organic-richness: a minimum present day total organic carbon (TOC) of
2-3 weight % (wt%) for shale-gas and 4-5 wt% for shale-oil, comprising
oil-prone kerogen;
Thermal maturity: an obvious criterion, ''gas window'' for shale-gas (VR
41.3% Ro) and ''oil window'' for shale-oil (VR of 0.7-1.3% Ro); and
Reservoir: in shale reservoirs, the key parameters controlling hydrocarbon
storage and flow, porosity, permeability and adsorption, are strongly re-
lated to the lithology and mineralogy of the rock, to the degree of natural
fracturing of the rock and the ability to artificially fracture the rock, which
is also affected by the present day tectonic stress regime.
