Crude Oil

&

Natural Gas

it is colorless, shapeless, and odorless in its pure form. natural gas consists of mainly Methane & it is clean burning and emits lower levels of potentially harmful byproducts into the air. it can also include ethane, propane, butane and pentane.

Typical Composition of Natural Gas

Methane CH4 70-90%

Ethane C2H6

0-20% Propane C3H8

Butane C4H10

Carbon Dioxide CO2 0-8%

Oxygen O2 0-0.2%

Nitrogen N2 0-5%

Hydrogen

sulphide H2S 0-5%

Rare gases A, He, Ne, Xe trace

The distinctive “rotten egg” smell that we often associate with natural gas is actually an odorant called mercaptan that is added to the gas before it is delivered to the end-user. Mercaptan aids in detecting any leaks. Natural gas is considered 'dry' when it is almost pure methane, having had most of the other commonly associated hydrocarbons removed. When other hydrocarbons are present, the natural gas is 'wet'.

Natural gas can be measured in a number of different ways. As a gas, it can be measured by the volume it takes up at normal or standard temperatures and pressures, commonly expressed in cubic feet. Production and distribution companies commonly measure natural gas in thousands of cubic feet (Mcf), millions of cubic feet (MMcf), or trillions of cubic feet (Tcf). STP: 1 atm. & 15 C. NTP: 1 atm. & 0 C.

natural gas is commonly measured and expressed in British thermal units (Btu). One Btu is equivalent to the amount of natural gas that will produce enough energy to heat one pound of water by one degree at normal pressure. To give an idea, one cubic foot of natural gas contains about 1,027 Btu.

Problem: what is the quantity of liquids in the following gas sample, p=900 psig, T=30 C?

The Formation of Natural Gas The most widely accepted theory says that fossil fuels are formed when organic matter (such as the remains of a plant or animal) is compressed under the earth, at very high pressure for a very long time.

At low temperatures (shallower deposits), more oil is produced relative to natural gas. At higher temperatures, however, more natural gas is created, as opposed to oil. a great deal of this methane will rise up into geological formations that 'trap' the gas under the ground. These formations are made up of layers of porous, sedimentary rock (kind of like a sponge that soaks up and contains the gas), with a denser, impermeable layer of rock on top.

Oil & Natural

Gas

From

Wellhead

to Burner Tip

1- The Exploration it must be remembered that the process of exploring for natural gas and petroleum deposits is rife with uncertainty and trial-and-error, simply due to the complexity of searching for something that is often thousands of feet below ground.

Seismic Exploration Arguably the biggest breakthrough in petroleum and natural gas exploration came through the use of basic seismology. Seismology refers to the study of how energy, in the form of seismic waves, moves through the Earth's crust and interacts differently with various types of underground formations.

Onshore Seismology In practice, using seismology for exploring onshore areas involves artificially creating seismic waves, the reflection of which are then picked up by sensitive pieces of equipment called 'geophones' that are embedded in the ground.

Recently, due to environmental concerns and improved technology, it is often no longer necessary to use explosive charges to generate the needed seismic waves. Instead, most seismic crews use non-explosive seismic technology to generate the required data. This non-explosive technology usually consists of a large heavy-wheeled or tracked-vehicle carrying special equipment designed to create a large impact or series of vibrations.

A Seismic Vibrator Truck

Offshore Seismology The same sort of process is used in offshore seismic exploration. When exploring for natural gas that may exist thousands of feet below the seabed floor, which may itself be thousands of feet below sea level, a slightly different method of seismic exploration is used. Instead of trucks and geophones, a ship is used to pick up the seismic data and hydrophones are used to pick up seismic waves underwater.

Exploratory Wells The best way to gain a full understanding of subsurface geology and the potential for natural gas deposits to exist in a given area is to drill an exploratory well. This consists of digging into the Earth's crust to allow geologists to study the composition of the underground rock layers in detail. In addition to looking for natural gas and petroleum deposits by drilling an exploratory well, geologists also examine the drill cuttings and fluids to gain a better understanding of the geologic features of the area.

APPRAISAL WELLS Yet to prove through Exploratory well and the presence of oil in the area of what is needed to determine the area of the contained reservoir for this oil, therefore, is drilling additional wells at distances of up to 2000 meters from the exploration well is these wells and tests are performed by more than the cost of the wells prior to that they are digging.

DEVELOPMENT WELLS

If it is proven from the results of wells evaluation and a tank of petroleum in the region contains large balances can output them economically would not mind drilling additional testing more cost-called well development can be obtained more accurate data and detailed and these wells are designed to serve productivity wells later. The results of each test wells in addition to the results of geological maps can be made a rough estimate of the quantity of oil or gas or both in the reservoir

2- The Extraction Once a potential natural gas deposit has been located by a team of exploration geologists and geophysicists, it is up to a team of drilling experts to actually dig down to where the natural gas is thought to exist. the process of drilling for natural gas is applied onshore and offshore

DRILLSHIP RIG

3- The Production is actually lifting the natural gas or oil out of the ground and processing it for transportation. the process of taking raw natural gas from underground formations and processing it into pipeline quality gas, ready for transportation

Well completion: Once a natural gas or oil well is drilled, and it has been verified that commercially viable quantities of natural gas are present for extraction, the well must be 'completed' to allow for the flow of petroleum or natural gas out of the formation and up to the surface.

This process includes strengthening the well hole with casing, evaluating the pressure and temperature of the formation, and then installing the proper equipment to ensure an efficient flow of natural gas out of the well.

Completing a well consists of a number of steps; installing the well casing, completing the well, installing the wellhead, and installing lifting equipment or treating the formation should that be required.

4- Natural gas processing natural gas found at the wellhead, although still composed primarily of methane, is by no means as pure. Raw natural gas comes from three types of wells: oil wells, gas wells, and condensate wells. Natural gas that comes from oil wells is typically termed 'associated gas'. This gas can exist separate from oil in the formation (free gas), or dissolved in the crude oil (dissolved gas). Natural gas from gas and condensate wells, in which there is little or no crude oil, is termed 'nonassociated gas'.

Methane commonly exists in mixtures with other hydrocarbons; principally ethane, propane, butane, and pentanes. In addition, raw natural gas contains water vapor, hydrogen sulfide (H2S), carbon dioxide, helium, nitrogen, mercury and other compounds. Natural gas processing consists of separating all of the various hydrocarbons and fluids from the pure natural gas, to produce what is known as 'pipeline quality' dry natural gas.

NGLs recovery

Estimate the recoverable liquids percentage in the following gas sample at 100 C, & 10 psig?

NGL recovery

NGL recovery

NGL recovery

5- The Transport Pipelines can be characterized as interstate or intrastate. Interstate pipelines carry natural gas across state boundaries, in some cases clear across the country. Intrastate pipelines, on the other hand, transport natural gas within a particular state.

6- The Storage

There are basically two uses for natural gas in storage facilities: meeting base load requirements, and meeting peak load requirements. As mentioned, natural gas storage is required for two reasons: meeting seasonal demand requirements, and as insurance against unforeseen supply disruptions. 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.

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

Natural gas is usually stored underground, in large storage reservoirs. There are three main types of underground storage: depleted gas reservoirs, 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.

7- The Distribution

is the final step in delivering natural gas to customers. While some large industrial, commercial, and electric generation customers receive natural gas directly from high capacity interstate and intrastate pipelines (usually contracted through natural gas marketing companies), most other users receive natural gas from their local gas utility, also called a local distribution company (LDC).

8- The Marketing

Natural gas marketing may be defined as the selling of natural gas. Marketing natural gas can include all of the intermediate steps that a particular purchase requires; including arranging transportation, storage, accounting, and basically any other step required to facilitate the sale of natural gas.

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