Well-log Analysis of Shale Gas Reservoirs

Reza Rezaee, M.Atif Iqbal

Well-logs provide continuous information about rocks and
their pore fluid properties. Typical well-logs such as
gamma-ray, density, neutron, sonic, and resistivity logs have
been traditionally used to estimate shale volume, porosity,
lithology, and fluid saturation in conventional oil and gas
exploration, where shale formations are treated as hydrocarbon
source rock and sandstone and carbonate formations are
reservoir rocks for the migrated oil and gas. However, welllogs
interpretation for unconventional shale plays do not
follow the same methodologies used for conventional sandstone
and carbonate reservoirs. This is due to the complex
nature and additional parameters that are required to be estimated
for shale reservoirs. Moreover, well-log methodologies
for reservoir-fluid characterization have been traditionally
advanced and calibrated for sandstone and carbonate rocks.
Nevertheless, certain novel concepts and emerging procedures
attempt to utilize well-logs for the evaluation of shale
reservoirs, including their organic richness, porosities, water
saturation, gas volumes, and geomechanical properties.