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Unconventional Gas Sources
Tight Gas
CBM
Gas Shales
US Has 211 tcf proved reserves
1,750 tcf technically recoverable
60% on shore reserves are unconvetional
Consumes 23 tcf/day
Produces 20 tcf/day
Gas Production
Gas Usage
• Shale Gas
• Wells produce from low perm shale
formations that are also the source for the
natural gas. Gas stored in the porosity and
macro porosity and can be adsorbed onto the
minerals or organic matter in the shale
• Tight Gas
• Wells produce from low porosity low
permeability sandstones or carbonites.
– Unconvental Gas
– Tight gas – Low Perm
– CBM – 10% of present production
– Gas Shales – 10% of present production
Background of Shale Gas
The first well drilled in 1821, Fredonia, NY
Some work in Ohio area pre WWII
First real big play Barnett in North Texas
Big Frac jobs 1987
Horizontal well 1992
Combined with stages frac jobs 1998
Gas Shales vs Tight Gas
The main difference is that the oil and gas shales are the source
rock for the hydrocarbons. In tight reservoirs the gas migrates
from the shale to the production formation, in the gas shales the
shale formationis so tight that the gas or oil cannot or is limited
in migrating out. The gas is stored in the porosity of both types
of reservoirs.
Factors in making a good gas shale field
Total Organic Content TOC
Thermal Maturity
Fracture network
Quartz and clay %
Formation Brittleness
Pressure gradient
Thickness
Porosity
Thermal Maturity
The breakdown of the organic material
Kerogen (pre oil gas)
The more mature the better
Vitrinite Reflectance
Carbon isotopes 13C to 12C
Many reservoirs will have different areas of maturity
shown by wet and dry areas
Eagle Ford
Characteristics of a reservoir
Barnett
7500 ft
Pressure 4000 psi
Temperature 200 F
Porosity 6%
Perm 250 nD
Adsorbed gas 35%
Pressure gradient .526 psi/ft
What works in Oil and Gas Shales
Some fields have been developed with Vertical wells
with large frac jobs
Most today are developed with Horizontal wells
with multi staged frac jobs
Some of the frac jobs can exceed 4,000,000 gallons
To quiet drilling operations