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Text 6. Natural Gas Storage
Natural gas, like most other commodities, can be stored for an indefinite period of time. The exploration, production, and transportation of natural gas takes time, and the natural gas that reaches its destination is not always needed right away, so it is injected into underground storage facilities. These storage facilities can be located near market centres that do not have a ready supply of local natural gas.
Traditionally, natural gas has been a seasonal fuel. That is, demand for natural gas is usually higher during the winter, partly because it is used for heat in residential and commercial settings. Stored natural gas plays a vital role in ensuring that any excess supply delivered during the summer months is available to meet the increased demand of the winter months. Natural gas in storage also serves as insurance against any unforeseen accidents, natural disasters, or other occurrences that may affect the production or delivery of natural gas.
There are basically two uses for natural gas in storage facilities: meeting base load requirements, and meeting peak load requirements. Base load storage capacity is used to meet seasonal demand increases. Base load facilities are capable of holding enough natural gas to satisfy long-term seasonal demand requirements. Typically, the turn-over rate for natural gas in these facilities is a year; natural gas is generally injected during the summer (non-heating season), which usually runs from April through October, and withdrawn during the winter (heating season), usually from November to March. These reservoirs are larger, but their delivery rates are relatively low, meaning the natural gas that can be extracted each day is limited. Instead, these facilities provide a prolonged, steady supply of natural gas. Depleted gas reservoirs are the most common type of base load storage facility.
Peak load storage facilities, on the other hand, are designed to have high-deliverability for short periods of time, meaning natural gas can be withdrawn from storage quickly, should the need arise. Peak load facilities are intended to meet sudden, short-term demand increases. These facilities cannot hold as much natural gas as base load facilities; however, they can deliver smaller amounts of gas more quickly, and can also be replenished in a shorter amount of time than base load facilities. Salt caverns are the most common type of peak load storage facility, although aquifers may be used to meet these demands as well.
Natural gas is usually stored underground, in large storage reservoirs. There are three main types of underground storage: depleted gas reservoirs, aquifers, and salt caverns. In addition to underground storage, however, natural gas can be stored as liquefied natural gas (LNG). LNG allows natural gas to be shipped and stored in liquid form, meaning it takes up much less space than gaseous natural gas.
Essentially, any underground storage facility is reconditioned before injection, to create a sort of storage vessel underground. Natural gas is injected into the formation, building up pressure as more natural gas is added. In this sense, the underground formation becomes a sort of pressurized natural gas container. In any underground storage facility, there is a certain amount of gas that may never be extracted.
In addition to this physically unrecoverable gas, underground storage facilities contain what is known as ‘base gas’ or ‘cushion gas’. This is the volume of gas that must be remain in the storage facility to provide the required pressure to extract the remaining gas.
‘Working gas’ is the volume of natural gas in the storage reservoir that can be extracted during the normal operation of the storage facility.
The most prominent and common form of underground storage consists of depleted gas reservoirs. Depleted reservoirs are those formations that have already been tapped of all their recoverable natural gas. This leaves an underground formation, geologically capable of holding natural gas. In addition, using an already developed reservoir for storage purposes allows the use of the extraction and distribution equipment left over from when the field was productive. Having this extraction network in place reduces the cost of converting a depleted reservoir into a facility. Depleted reservoirs are also attractive because their geological characteristics are already well known. Of the three types of underground storage, depleted reservoirs, on average, are the cheapest and easiest to develop, operate, and maintain.
Aquifers are underground porous, permeable rock formations that act as natural water reservoirs. However, in certain situations, these water containing formations may be reconditioned and used as natural gas storage facilities. As they are more expensive to develop than depleted reservoirs, these types of storage facilities are usually used only in areas, where there are no nearby depleted reservoirs. Traditionally, these facilities are operated with a single winter withdrawal period, although they may be used to meet peak load requirements as well.
In order to develop a natural aquifer into an effective natural gas storage facility, all of the associated infrastructure must also be developed. This includes installation of wells, extraction equipment, pipelines, dehydration facilities and possibly compression equipment. Since aquifers are naturally full of water in some instances powerful injection equipment must be used to allow sufficient injection pressure to push down the resident water and replace it with natural gas.
Underground salt formations offer another option for natural gas storage. These formations are well suited to natural gas storage in that salt caverns, once formed, allow little injected natural gas to escape from the formation unless specifically extracted. The walls of a salt cavern also have the structural strength of steel, which makes it very resilient against reservoir degradation over the life of the storage facility, it is necessary to develop a ‘salt cavern’ with the formation.
Essentially, this consists of using water to dissolve and extract a certain amount of salt from the deposit, leaving a large empty space in the formation. Salt caverns may be replenished more quickly than other types of underground storage facilities.
Exercise 84. Translate the following words and word combinations.
Natural gas storage, indefinite period of time, right away, underground storage facilities, residential and commercial settings, stored natural gas, vital role, meet the increased demand, unforeseen accidents and natural disasters, maintain the reliability of supply, base load storage capacity, turn-over rate, relatively low, pressurized natural gas container.
Exercise 85. Write the verbs related to the following nouns. Use them in your own sentences.
Recovery, storage, extraction, compression, withdrawal, development, demand, generation, requirement, injection, recognition.
Exercise 86. Write the nouns derived from the following verbs. Define the suffixes used to form the nouns. Translate them.
Explore, produce, transport, locate, apply, deliver, occur, maintain, mean, pressurize, contain.
Exercise 87. Use the prefixes: in-, un-, ir-, mis-, dis- to form the opposites of the following words.
Definite, usual, available, foreseen, reliable, capable, limited, essential, regular, understand, lead, expensive, significant, solve.
Exercise 88. Give words which mean the opposite of those given below.
Shallow, comparable, available, expected, increase, foreseen, safe, strengthen, regulation, closely, store, porous, long-term, recoverable, predictable.
Exercise 89. Work in pairs. Make questions for each answer below with reference to the text.
1. The initial function of underground gas storage is to balance gas consumption and resources at all times.
2. Natural gas is stored in underground facilities.
3. The relative peak demand is on the coldest day of the year.
4. The cavern is initially developed by using conventional solution mining.
5. This improved process has numerous advantages.
6. Savings made by technical innovation in reservoir and aquifer storage can be estimated.
7. In 2015 world-wide natural gas demand could reach 3,300 – 3,400 10 9m3.
8. Gas storage in depleted fields is the most widespread method in the world and often the least expensive.
9. The profits to be made due to price fluctuations can be considerable.
10. Development of gas storage in the United States during recent years has resulted in an increase in yearly production capacity.
Exercise 90. Put the verb in brackets into the correct voice and tense form (Present Perfect or Past Simple). Translate the sentences.
1.Underground gas storage (develop) rapidly in recent years.
2.The growth of international trade (profit) increasingly due to the development of storage facilities.
3.In 1996 – 1997 there (be) 580 underground storage sites world wide.
4.Storage in porous rocks (become) the most convenient way of storing gas in order to meet winter demand.
5.The volume of working gas world-wide (triple) since 1970.
6.Horizontal drilling (appear) in the 1980’s in some areas of oil production.
7.Storage (use) to serve only as a buffer between transportation and distribution.
8.Underground natural gas storage facilities (grow) in popularity shortly after World War II.
9.Prior to 1950, virtually all natural gas storage facilities (be) in depleted reservoirs.
10. The Environmental Protection Agency (set) certain rules and restrictions on the use of aquifers as natural gas storage facilities.
Exercise 91. Put the verbs in brackets into the correct Active or Passive tense forms. Translate the sentences.
1. The combination of the two types of storage (use) to guarantee basic demand to meet seasonal variations.
2. Storage needs (vary) enormously from country to country, depending on the energy situation.
3. Underground gas storage facilities (build) in hydrocarbon reservoirs, aquifers and salt caverns.
4. The technique of gas storage in salt caverns (gain) recognition.
5. Today, detailed seismic monitoring (allow) small structures (to spot).
6. The specialists know how gas (distribute) in the facility at any moment and at any place.
7. These operations (take place) under very different practical conditions and each of them (design) so that the withdrawn gas can (send) out without any constraints over several decades.
8. Due to recent technology development costs (halve) since 1990’s.
9. Gas (store) when prices on it are low and (sell) when prices are high.
10. The most prominent and common form of underground storage (develop) after the World War II.
Exercise 92. Ask:
a) if natural gas storage plays a vital role in maintaining the reliability of supply;
if natural gas has been a seasonal fuel;
if storage facilities are located near market centres;
if demand for natural gas during the summer months is now increasing.
b) how natural gas is stored;
what the term “working gas” means;
when the pressure inside the storage facility is the highest;
what advantages underground gas storage has;
where the first instance of natural gas being stored underground occurred.
Exercise 93. Match the term and its definition.
| Terms | Definitions |
| 1. Total gas storage capacity | a) the volume of gas that is intended as permanent inventory in a storage reservoir. |
| 2. Base gas / cushion gas | b) a measure of the amount of gas that can be delivered from a storage on a daily basis. |
| 3. Working gas | c) the maximum volume of natural gas that can be stored at the storage facility. |
| 4. Deliverability | d) the amount of gas that becomes permanently embedded in the storage facility. |
| 5. Physically unrecoverable gas | e) the average number of times a working gas volume can be turned over during a specific period of time. |
| 6. Cycling rate | f) total gas in storage, available to the market place at a particular time. |
Exercise 94. Translate into English.
1. Підземні сховища природного газу розташовані, як правило, неподалік від ринків збуту. 2. Потреба у природному газі зростає протягом холодних місяців, тому що великий об’єм газу використовується для опалення помешкань. 3. Існує три основних типи підземних сховищ природного газу: резервуари у вичерпаних родовищах газу або нафти, водоносних шарах та соляних відкладеннях. 4. У будь-якому підземному сховищі природного газу існує певна його кількість, яка ніколи не відкачується. 5. Продуктивність будь-якого підземного сховища визначається пропускною спроможністю та об’ємом газу, який буде відкачений у разі необхідності. 6. Створення сховища природного газу у соляній шахті – доволі складний і дорогий процес. 7. Існує ряд обмежень у використанні водоносних шарів для формування підземних сховищ природного газу. 8. Підземні сховища природного газу гарантують безперервне постачання протягом року.
Exercise 95. Select the key words and expressions from text 6 and be ready for the discussion on the following topics:
1) Commercial benefits of using underground gas storages;
2) Advantages and disadvantages of each type of underground natural gas storage
Exercise 96. Memorize the following words and word combinations to text 7.
Transport – транспортувати, переміщати
oil transport system – система нафтопроводів
total – загальний
length – довжина
oil pumping station – нафтоперекачувальна станція
deliver – постачати
tank – резервуар
farm – господарство, парк (технічний)
trunk – магістраль
oil pipeline – нафтопровід
Open Joint-Stock Company – Відкрите Акціонерне Товариство
subsidiary company – «дочірня» компанія
enterprise – підприємство
marine – морський
terminal – термінал
associate – пов’язувати, співвідносити
function – функціонувати, працювати, діяти
commission – вводити в експлуатацію
design – проект; проектувати; призначати
enter – входити; вводити
stage – стадія
oil production – видобуток нафти
growth – зростання, нарощування (видобутку)
satisfy – задовольняти
take advantage of – скористатися чимось
accept – приймати
reverse – реверсний, зворотній
fill – наповнювати
Exercise 97. Read and translate text 7.