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Welcome the Hydrators
Use of Hydrates for Natural Gas Storage
Objective
Major gas storage methods: Aquifers Depleted Gas Reservoirs Salt Caverns
Proposed method: Hydrates
The three major methods of storing natural gas are compared with the use of hydrates.
OutlineUse of Depleted Reservoirs
Use of Aquifers
Natural Gas Storage - A brief history
“After WW II, natural gas consuming countries noticed that the seasonal demands for natural gas could not possibly be met by then present pipeline delivery methods alone. The sizes and deliverability of pipelines would have to be increased dramatically to meet this challenge. The technology to construct such pipelines to transport the gas to major consumers was unattainable. Thus began the natural gas storage movement”.
Why Hydrates as Storage Method?
Cost factor Hydrates could be relatively cheaper than
other forms of storage method. Hydrates can be used for economic storage of
natural gas in cold countries and the associated cost can be relatively minimized.
Accessibility Tanks can be easily accessed when needed
especially during peak periods.Safety
Incase of an explosion, hydrates burn slowly due to the presence of ice.
Natural Gas Hydrates
Gas hydrates are naturally occurring solids composed of water molecules forming a rigid lattice cage containing molecule(s) of natural gas.
Natural Gas Hydrate Structure
Options for Storage
Pressurized Tank
Refrigerated Tank
Natural Gas Hydrates
• Pressure = 6MPA and Temperature = 293K
Natural Gas Hydrates
Hydrates production
Storage for water and gas mixture
Slurry mixture
Gas
Heat
V-14
Gas and water slurry after depressurizing
Recycled water flowing back to the system
Water removed
Hydrates gas recovery diagram
Pressurized tank in order to reduce cost.Volume of tank needed was found by
Where Q is the inlet flow rate of gas, and R is the rate of formation of hydrates.
Important Factors: Temperature and Pressure
Storage Method for Hydrates
Where R is the rate of hydrate formation, μ2
is the second moment of distribution around particle size for hydrate; f is the fugacity of gas, feq is the fugacity of gas at equilibrium, and K* is the kinetic parameter
Volume of reactor used for Hydration/Storage
Pressurized Tank
Gas Supply
Pump
Storage for water/gas mixture
Gas and water slurry supply after storage
Gas and water mixture
Flare gas
water
Fresh water supply
Recycle water
Fresh water supply
Compressor 129KW
Gas supply
V-2 V-3
V-4
Fresh water supply
V-5
V-6
Pressurized vessel heated
Heat
V-13
Process flow diagram for Hydrates
Depleted Gas Reservoirs
These are naturally occurring gas reservoirs that have been tapped of all recoverable natural gas.
Began in Ontario, Canada 1915.
Important Selection factors
PorosityPermeability
Cushion Gas
Injection Well
Withdrawal well
Pump
Valve
Compressor
‘the Hydrators’ Natural Gas Delivery
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Call: 1-800-Methane
Gas gathering pipeline
Wellheads
Working Gas
Depleted Gas Reservoir
Depleted Gas Reservoirs
Well-understood geological make-
up.
Existing gas processing facilities.
Primarily used for base-load gas
storage.
Depleted Reservoirs – Unique characteristics
Advantages
Large storage volume
Short development period
Disadvantages
Demands ready market
Requires low permeability
Poor regional spread
Aquifers
An aquifer storage field is a sub-surface facility for storing natural gas.Aquifers are water bearing sands topped by an impermeable cap rock
Aquifers
Summary of parameters used
Avg. Bottom Hole pressure 7.3 MPaTop pressure 101325 Pavolumetric flow rate 100 m3/smass flow rate 4302 kg/sDensity 0.717 kg/m3k 1.31Length of Pipe 100 m
Aquifers
Aquifers require cushion gas of up to 80% of total volume which make its utilization very high. Aquifers are mostly built when the price of natural gas is low.
P-19
E-9
compressor
Gas supply
V-2 V-3
V-1
Aquifer Underground Storage
Withdrawal pipe
Injection of gas
Withdrawal pipe
V-12
Process flow diagram for Aquifers
Aquifers
Land for Aquifers Must be well spaced at least 320-640 Acres apart Must be located no less than
100 feet from private homes 150 feet from public streams 50 feet from any streams
Land cost= $/acre × amount of acre used for storage (including restrictions)
Salt Caverns
These are large underground cavities created inside salt domes/deposits using leaching (solution mining) techniques.
Relatively new gas storage method (Began by SMGC in 1961).
Increasingly popular method of natural gas storage. Primarily located along the Gulf Coast (Texas, Louisiana, Mississippi and Alabama).
Solution mining technology
Valve
‘the Hydrators’ H2O Delivery
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Call: 1-800-Solvent
Salt Dome
Salt Caverns
I/W well
Salt cavern formation
Cushion Gas
Injection Well
Withdrawal well
Pump
Valve
Compressor
‘the Hydrators’ Natural Gas Delivery
How’s my driving?....
Call: 1-800-Methane
Gas gathering pipeline
Wellheads
Working Gas
Salt Cavern
Salt Caverns
Salt Caverns
Salt Caverns – Unique characteristics
Storage development technology.
Smaller storage capacity.
Primarily used for peak shaving
gas storage.
Advantages
Cavern volume control
Low permeability
Minimal cushion gas requirement
Disadvantages
Smaller storage volume
Expensive development technology
Environmental concerns
Wells Valves Compressors Cushion gas Utilities
(Electricity) Pumps Land / Labor Installation costs Pressurized tanks
Gathering system Gas flow meters Dehydrators Separators Property
Taxes/Insurance Drilling Leaching
Development cost factors
Gas storage cost breakdown
As conduits for the transport of gas into and from the earth, they are an important part of any gas storage facility.Primary Gas well components:• Well casing• Well tubing Average number of gas wells is between 2 and 4 per storage facility.
Compressors are one of the most expensive components of any gas storage facility.Compressor-incurred costs come from power requirements, equipment material, etc.
Compressor power calculation
Gas storage cost breakdown
Cushion Gas
Provides the minimum
deliverability pressure
required by law.
Influences storage cost based on its ratio to the
working gas.
Current market price for natural
gas is approximately
$4.00 per mmbtu.
Costs also include
injection, withdrawal and storage costs.
Gas storage cost breakdown
Utilities (Electricity)Gas compressors and pumps are powered by electricity and this adds to the storage facilities total cost. •Storage capacities influence electrical power requirements which in turn influence total cost.•Electricity costs were calculated from compressor and pump power requirements.
Pumps• Pumps are required to aid gas delivery when the reservoir pressure is not high enough.• Pump incurred costs come from pump material and deliverability rates.• Deliverability = Withdrawn gas volume(mmscf)/withdrawal period(days).• They can be omitted if reservoir pressure is high enough.
Gas storage cost breakdown
Land• Leasing or outright purchase of storage
facility land is an important cost item.• Land is leased on a yearly basis. • Can be estimated as a fraction of the total
capital investment.
Labor• Labor is also an integral part of total cost
calculations.• Labor cost calculations came from total
development and withdrawal time periods. • Estimated using semi-skilled labor pay
rates(~$30.00/hr basis).
Installation costs Cost Factors
Include miscellaneous costs
associated with installing purchased
equipment and sometimes
associated labor.
Installation costs were
derived as a percentage of
equipment cost.
Gas storage cost breakdown
Gas storage cost breakdown
Depleted Gas Reservoirs
Wells• Average depth of 5500ft.• Well casing and tubing made from
medium grade steel.• Combined weight of well material is ~
6 lbs/ft• Current cost estimates of medium
grade steel = $1000/ton• Total costs = $35,000,000.00
Depleted Gas Reservoir
Compressors• The basic compressor equation was used
to estimate the compressor power requirements.
• Horse power estimates came up to 41,795 theoretically.
• Resulting total compressor cost estimate was approximately $7,877,987.14 .
Depleted Gas Reservoir
Cushion gas
Occupied half of the total gas
reservoir volume.
Purchase cost of gas is
approximately $4.00 per mmbtu.
We used estimates of
$4.00 per mmbtu.
Total cushion gas cost
estimates = $22 million for a
max. capacity of 10 BCF.
Depleted Gas Reservoir
Pumps•Pump costs were calculated using the gas delivery flow rates.•Pump cost estimates were approximately $418,619.79.
Electricity•Estimated from the horsepower requirements of the compressor and pump. •Total estimates equal $6,370,695.01 .
Depleted Reservoirs
Land:•Leasing cost estimates came up to about$250,000 per year.
Labor:•Estimated at $192,000 over the activation/injection and withdrawal period.
Installation costs:•Combined total of percent equipment costs, approximately 40 million dollars.
Total cost estimate=$30 million per BCF.
Salt Caverns
Salt Caverns
Salt Caverns
0 2000000 4000000 6000000 8000000 10000000 12000000$0.00
$20.00
$40.00
$60.00
$80.00
$100.00
$120.00
Comparing the effects of natural gas prices in Aquifer cost calculations
$ 4 cushion gas$2 cushion gas$6 cushion gas$8 cushion gas
capacity in mmbtu
$/m
mbtu
0
1000
000
2000
000
3000
000
4000
000
5000
000
6000
000
7000
000
8000
000
9000
000
1000
0000
$0.00
$20.00
$40.00
$60.00
$80.00
$100.00
$120.00
$140.00
$160.00
$180.00
$200.00TCI of Acquifer compared to Hydrates
HydratesAquifer at $4/mmbtuaquifer at $6/mmbtuAquifer at $8/mmbtu
Capacity in mmbtu
TC
I/m
mbtu
0 2000000 4000000 6000000 8000000 10000000 120000000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
ROI of Hydrates vs. Aquifer at different Natural gas prices
HydratesAquifer at $4 cushion gasAquifer at $6 cushion gasAquifer at $8 cushion gas
Capacity in mmbtu
RO
I
Cost Summary
Summary Results for Aquifers and Hydrates
Hydrates Aquifers
Compressor $291,466.80
Pumps $83,333.34
Cushion Gas - $32,000,000.00
Extra Fees $1,800,000.00
Land $45,000.00 $25,000,000.00
Utilities $42,000.00
Pressurised Tank $24,625,109.00 -
Valves $182,625.97
Pipes $181,779.20
TCI/mmbtu $15.18 $35.65
ROI 0.66 0.28
Total Cost $25,591,314.31 $60,113,205.31
0.00E+00 2.00E+06 4.00E+06 6.00E+06 8.00E+06 1.00E+07 1.20E+07$0.00
$20.00
$40.00
$60.00
$80.00
$100.00
$120.00
$140.00
$160.00
$180.00
$200.00
$220.00
Cost Comparison for typical Salt cavern and Depleted reservoir
D.R. at $2.42/mmbtuD.R at $4.42/mmbtuD.R. at $6.42/mmbtuD.R at $8.42/mmbtuS.C at $2.42/mmbtuS.C at $4.42/mmbtuS.C at $6.42/mmbtuS.C at $8.42/mmbtu
mmbtu
$/m
mbt
u
0.00E+00 1.00E+06 2.00E+06 3.00E+06 4.00E+06 5.00E+06 6.00E+06 7.00E+06 8.00E+06 9.00E+06 1.00E+070.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
Return on Investment
D.G.ReserviorSalt cavern
MMBTU
ROI
Conclusions
Equipment Cost for Hydrates is not as expensive as other existing forms of storage.
Return on Investment is Higher than other compared methods.
Accessibility/mobility factors favor hydrates.
Conclusions/Recommendations
● Hydrates can be used for economic storage of natural gas in countries with colder climates. ● Associated costs of natural gas storage using hydrates can be relatively minimized.● The use of natural gas hydrates for storage is an alternative that maintains a high degree of safety. An ignited gas hydrate mass burns slowly and doesn’t explode due to the presence of frozen water molecules.
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