Presentation on theme: "Welcome the Hydrators Busola Odunuga & Ben Aseme Use of Hydrates for Natural Gas Storage."— Presentation transcript:
Welcome the Hydrators Busola Odunuga & Ben Aseme 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.
Outline Gas Hydrates Storage Use of Depleted Reservoirs Use of Salt CavernsUse 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 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, μ 2 is the second moment of distribution around particle size for hydrate; f is the fugacity of gas, f eq is the fugacity of gas at equilibrium, and K * is the kinetic parameter
Volume of reactor used for Hydration/Storage V=Q/R, where V is the volume of the reactor, Q is the gas flow rate in the reactor, R is the rate of hydrate formation. 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 Important Selection factors Porosity Permeability
Cushion Gas Injection Well Withdrawal well Pump Valve Compressor ‘the Hydrators’ Natural Gas Delivery How’s my driving?..... Call: 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 volumeShort 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 pressure7.3MPa Top pressure101325Pa volumetric flow rate100m3/s mass flow rate4302kg/s Density0.717kg/m3 k1.31 Length of Pipe100m
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. Process flow diagram for Aquifers
Aquifers Land for Aquifers Must be well spaced at least 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’ H 2 O Delivery How’s my driving?.... Call: 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: Methane Gas gathering pipeline Wellheads Working Gas Salt Cavern Salt Caverns
Salt Caverns – Unique characteristics Storage development technology. Smaller storage capacity. Primarily used for peak shaving gas storage. Advantages Cavern volume controlLow 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 Wells 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 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 k=ratio of natural gas specific heats Z1=compressibility factor T1=Suction-side temperature in degrees Kelvin P2=Discharge-side pressure in psia P1=Suction-side pressure in psia Q=flow rate in Million Standard ft 3 per day HP = Theoretical Horsepower
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. Piping: 35% Valves: 28% Pumps: 30% Flow meters: 30% Dehydrators: 22.5% Compressors: 20% Separators: 25% Gas storage cost breakdown
Property Taxes/Insurance Property taxes are in the range of 2 to 4 percent for highly populated areas and in the range of 1 to 2 percent for less populated areas. Property insurance is about 1 percent the total fixed capital investment per year. “Nothing is certain but death and taxes” – Benjamin Franklin( , American founding father and polymath).
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,
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, Electricity Estimated from the horsepower requirements of the compressor and pump. Total estimates equal $6,370,
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 Compressors Total estimated cost = $2,363, Valves Estimated cost = $48, Wells Estimated total cost =$26,525,000.00
Salt Caverns Pumps Total cost = $209,000 Electricity Total cost estimate = $63,400 per BCF Cushion gas Total cost estimate = $1,500,000 per BCF
Salt Caverns Total cost estimate=$14 million per BCF Installation costs Total estimate =$5,000,000 Piping Estimated at $300,000 per BCF Land Total lease estimate = $257,000 per yr.
Cost Summary Summary Results for Aquifers and Hydrates HydratesAquifers Compressor$291, Pumps$83, Cushion Gas-$32,000, Extra Fees$1,800, Land$45,000.00$25,000, Utilities$42, Pressurised Tank$24,625, Valves$182, Pipes$181, TCI/mmbtu$15.18$35.65 ROI Total Cost$25,591,314.31$60,113,205.31
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.