Fluid handling – Processes
Reexamination Certificate
2001-05-25
2003-06-24
Lee, Kevin (Department: 3753)
Fluid handling
Processes
C137S236100, C062S260000
Reexamination Certificate
active
06581618
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to shallow depth and low pressure gas facilities and related methods of use to balance pipeline systems, supply customers, maximize gas storage and the like during periods of operations of fluctuating demand and supply of gas and normal operations.
BACKGROUND ART
Natural Gas, also known as methane, is a colorless, odorless, fuel that burns cleaner than many other traditional fossil fuels. As used herein, the term “gas” means and includes any gas, including natural gas. The term “diverted,” pump,” “pumped,” “pumping,” “compress,” “compressing,” “compressed,” and the like shall mean channeling, compressing, and diverting. As used herein, the term “line” or “lines” shall mean and include pipes, lines, channels, and the like. It is one of the most popular forms of energy today. It is used for heating, cooling, production of electricity and it finds many uses in industry. Increasingly, natural gas is being used in combination with other fuels to improve their environmental performance and decrease pollution.
Natural gas is most commonly produced by drilling into the Earth's crust. A well or bore-hole is drilled into pockets of natural gas that have been trapped below the surface of the Earth. The natural gas is then compressed or piped to the Earth's surface. Once the gas is brought to the surface, it is refined to remove impurities, like water, other gasses, and sand.
Then it is transmitted through large pipelines that span the continent and the world. In fact, natural gas has become a very important commodity.
To begin with, natural gas must be purchased by some entity. Factories and electric power plants may get gas directly from the pipeline using arrangements made through a marketer, supplier or producer. Residential and smaller businesses generally buy gas from a local distribution company or utility. Further, as discussed above, just like any other commodity, natural gas must be produced, sold and shipped to its end users. However, unlike other commodities, natural gas cannot be stored by the customer in a warehouse until it is utilized. Because of its gaseous nature and volatility, one of the most economically viable manners of storing natural gas is in specialized underground warehouses called natural gas storage fields. These storage fields consist of underground caverns, hollowed out salt domes, depleted natural gas and oil fields, or in some cases water-filled domes.
Underground storage, in common usage, is gas transferred from the reservoir of discovery to other reservoirs, usually closer to market areas, where it is stored until needed to meet market demand. Natural gas is stored in underground reservoirs primarily to ensure the capability of the gas industry to meet seasonal fluctuations in demand. Underground storage supplements the industry's production and delivery systems, allowing supply reliability during periods of heavy gas demand by residential and commercial consumers for space heating. Prior art storage facilities have utilized high pressure storage of natural gas to meet these demands.
These storage facilities/fields act as a buffer between the pipeline and the distribution system of the natural gas. Storage allows distribution companies to serve their customers more reliably by withdrawing more gas from storage to meet customer demands during peak use periods. It also allows the sale of fixed quantities of natural gas on the spot market during off-peak periods. Having local storage of gas also reduces the time necessary for a delivery system to respond to increased gas demand. Storage also allows continuous service, even when production or pipeline transportation services are interrupted. However, the time required to withdraw gas and the time required to re-fill these storage facilities is a source of great time, expense and danger to suppliers, consumers and the like.
For example, there are well more than 400 underground storage sites in 27 states across the United States and Canada. Together, these sites can hold upwards of 3, quads of natural gas, ready to be withdrawn at any time. (A quad is an abbreviation for a quadrillion (1,000,000,000,000,000) Btu. For natural gas, roughly equivalent to one trillion (1,000,000,000,000) cubic feet, or 1 Tcf.) Despite these high numbers, storage capacity is always increasing in order to accommodate increased gas usage and improve reliability. However, the underground storage of today is drastically limited in its operational uses and abilities.
The three principal types of underground storage sites used in the United States today are: (1) depleted reservoirs in oil and/or gas fields, (2) aquifers, and (3) salt formations. Each type has its own physical characteristics (porosity, permeability, retention capability) and economics (site preparation costs, deliverability rates, cycling capability), which govern its suitability to particular applications. As used herein, the term gas storage facility means and refers to any of the three principal types of underground storage sites, i.e. depleted reservoirs, aquifers, and salt formations.
Most existing gas storage in the United States is held in depleted natural gas or oil fields located close to consumption centers. Conversion of a field from production to storage duty takes advantage of existing wells, gathering systems, and pipeline connections. The geology and producing characteristics of a depleted field are also well known. However, choices of storage field location and performance are limited by the inventory of depleted fields in any region.
The reservoir rock of an underground storage cavern in which natural gas is normally stored consists of porous sandstone and limestone. It is quite common that these formations can contain 30% or more pore space by volume. In common cases, the gas is pressurized and injected into the storage reservoir as desired. Further, as desired, the injected natural gas may be produced from the storage reservoir when needed. Accordingly, the art field is in search of a method of utilizing depleted field storage facilities to obtain an utmost benefit.
In some areas natural aquifers have been converted to gas storage reservoirs. An aquifer is suitable for gas storage if the water-bearing sedimentary rock formation is overlaid with an impermeable cap rock. While the geology of aquifers is similar to depleted production fields, their use in gas storage usually requires base (cushion) gas and greater monitoring of withdrawal and injection performance. Deliverability rates of aquifers have been enhanced by the presence of an active water drive. However, the use of aquifers as natural gas storage is, like depleted fields, limited by the presence of an aquifer. Accordingly, the art field is in search of a method of utilizing aquifer storage facilities to obtain an utmost benefit.
Salt formation storage facilities provide very high withdrawal and injection rates compared with their working gas capacity. Base gas requirements are relatively low. To date, the large majority of salt cavern storage facilities have been developed in salt dome formations located in the Gulf Coast States. Salt caverns leached from bedded salt formations in Northeastern, Midwestern, and Western States are also being developed to take advantage of the high volume and flexible operations possible with a cavern facility. The ability to perform several withdrawal and injection cycles each year has made salt formation facilities very popular in recent years. Accordingly, the art field is in search of a method of utilizing salt formation storage facilities to obtain an utmost benefit.
Additionally, storage facilities are classified as seasonal supply reservoirs (depleted gas/oil fields and aquifers for the most part) and high-deliverability sites (mostly salt cavern reservoirs). Seasonal supply sites are designed to be filled during the 214-day nonheating season (April through October) and drawn down during the 151-day heating season (November through March). High-deliverability sites are situated to pro
Grimes Paul J.
Hill Ross K.
Canatxx Energy, L.L.C.
Lee Kevin
The Matthews Firm
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