The production, processing, transmission, and
distribution of oil and natural gas is the second largest anthropogenic (human-influenced)
methane source worldwide, releasing as much as 88 billion cubic meters (BCM) or
343 million metric tons of carbon equivalent (MMTCE) of methane to the atmosphere
annually. Although natural gas is a clean source of energy, methane losses from
natural gas systems account for 18% of total worldwide methane emissions. In India,
of the total methane emissions, 5% result from the oil and natural gas sector.
Emissions
primarily result from operations, routine maintenance, and system disruptions.
Emissions vary greatly from facility to facility and are largely a function of
operation and maintenance procedures and equipment conditions. The following table
represents methane emissions from the oil and gas sector in selected countries:
International
Methane Emissions from Natural Gas and Oil Infrastructure
Methane Emissions (MMTCE)
Country
1990
2000
2010
(projected)
Russia
91.6
69.1
74.7
United States
40.3
37.8
39.6
Ukraine
19.6
16.4
10.6
Venezuela
11.0
14.3
18.6
Uzbekistan
7.4
9.2
11.7
India
3.5
6.7
15.0
Canada
4.7
6.4
6.5
Mexico
3.0
4.2
6.0
Argentina
2.2
3.7
8.3
Thailand
0.8
2.3
4.3
China
0.2
0.4
1.3
(Source: Methane
to Markets Fact sheet, August 2006)
Characteristics
of Natural Gas
Typical composition of natural gas
includes 92.69% methane, 3.43% ethane, 2.18% nitrogen, 0.71% propane, 0.52% carbon
dioxide, 0.15% n-butane, 0.12% iso-butane, 0.11% hexane, and 0.09% pentane. Natural
gas has zero SOx emission and is low on NOx and CO2 emissions, making it an environmentally
benign fossil fuel than coal. In India , natural gas is found both alone and alongwith
crude oil. The following table represents the characteristics of Indian natural
gas.
Characteristics
Natural gas
Colour
Clear
bright appearance
Colour,
saybolt
+10
Pressure
(psi)
10
Octane
number
127
Specific
CO2 emission factor for electricity generation (kg CO2/kwh gas)
0.065
Sulphur (ppm)
100
(Source:
Shiv Pratap Raghuvanshi, Renu Singh, A. K. Raghav, and A. Chandra Indian Institute
of Technology )
Natural
Gas Reserve in India
Indian reserve of natural
gas is about 0.04% of the world proven reserves of hydrocarbons. Geological resources
of hydrocarbons in the country are estimated at 21.31 billion tonnes of which
61% are offshore and 39% on land. Half of the resources represent natural gas
of which only 12% has been established. Gas based power generation is over 12000
MW (11% of the total installed base in the country). The ratio of demand of natural
gas from power sector to that from fertilizer plants will change from 0.32 to
1.89% indicating a major increase in demand from the power sector as against a
stagnant demand from the fertilizer sector (www.gdib.org). India accounts for
only 1 % of the world's natural gas consumption. Main reasons for the low share,
in spite of high efficiency of natural gas are, firstly, coal is an abundant and
cheap resource, and secondly, the supply of indigenous natural gas is minimal.
( Source: Shiv Pratap Raghuvanshi, Renu Singh, A. K.
Raghav , and A. Chandra Indian Institute of Technology )
Recovery
and Use Opportunities
In oil and natural
gas systems, methane emissions can be reduced by upgrading technologies or equipment
and by improving management practices and operational procedures. Opportunities
to reduce methane emissions generally fall into one of three categories:
Technologies or equipment upgrades, such as low-emission
regulator valves, that reduce or eliminate equipment venting or fugitive emissions.
Improvements in management practices and operational procedures
to reduce venting.
Enhanced management practices, such
as leak detection and measurement programs, that take advantage of improved measurement
or emission reduction technology.
Cost-effective opportunities
for reducing methane emissions in the oil and gas sector vary greatly from country
to country based on the levels of physical and institutional infrastructure. Many
of the available cost-effective abatement options and technologies, however, can
be applied universally throughout the oil and gas industry.
Issues
for Project Development
Although there are
many effective ways to reduce methane emissions in the oil and gas sector, several
issues are important to successful project development. Some of the key issues
include:
Recognizing leak prevention and mitigation as
a core business opportunity and directing available capital toward leak reduction
projects.
Making project investments economically viable
in areas where there are artificially low natural gas prices.
Providing
robust information on and access to the many available emission reduction technologies
and management practices.
Identifying and addressing specific
regulatory barriers that might inhibit project development.
Improving
and expanding existing markets and creating new markets for methane gas.
Methane
leaks and other fugitive emissions along the natural gas industry's supply chain
represent product losses that can be avoided using readily available, cost-effective
practices and technologies.
Possible
Technologies for Reduction of Methane
As with most
emerging natural gas economies, India currently has limited natural gas infrastructure,
specifically within the transmission and distribution sub-sectors. For example,
in the late 1990s India built its first natural gas pipeline, spanning 1,700 km.
Consequently, while many of the cost effective options within these sub-sectors
currently offer limited emission reduction potentials, this may change as infrastructure
expands to meet rising natural gas consumption demand.
New
technologies have also been developed such as the Infrared camera, which can be
effectively used to detect leakages from oil and natural gas supporting infrastructure.
These infrared cameras allow for detection of hydrocarbon emissions. With the
help of this technology, emissions that were once invisible have become now visible
and easily traceable.
The following table represents natural
gas infrastructure emission mitigation options:
No
Abatement
Option
Description
Reduction
Efficiency
Applicable
sub sector
1
Install vapour recovery units
During
crude oil storage, light hydrocarbons vapourise out of solution and vent to the
atmosphere. Vapor recovery units capture these vapours for fuel or sales.
95%
Crude oil storage tanks
2
Install
flare systems
Flaring
devices burn vented gas, thus converting methane to carbon dioxide. Applicable
to onshore and offshore gas wells.
95%
Natural gas production
3
Install
plunger lift system
Instead of venting gas wells
to the atmosphere to expel accumulated well bore fluids, a plunger lift uses the
wells energy to efficiently push the fluids out of the well.
4%
Natural gas production
4
Green
completions
After
drilling new wells, instead of venting the well to remove debris from around the
well bore, green completions use additional separator traps and dehydrators t
route gas to sales.
70%
Natural gas production
5
Install
flash tank separators in production
Flash tank separators are
used to recover methane from tri-ethylene glycol for fuel or sales, minimizing
venting with water vapour.
54%
Natural gas production
6
Install
flash tank separators in processing and transmission
Flash tank separators are
used to recover methane from tri-ethylene glycol for fuel or sales, minimizing
venting with water vapour.
54%
Natural gas processing and
transmission
7
Replace high bleed pneumatics
with low bleed devices
Natural gas powered pneumatic
devices are designed to emit natural gas as part of their normal operations. Such
systems can be replaced with low bleed pneumatics
86%
Natural gas processing and
transmission
8
Replace with high bleed pneumatics
with instrument air systems
Natural gas powered pneumatic
devices can be replaced with compressed. Dried air systems, eliminating methane
emissions
100%
Natural
gas processing and transmission
9
Composite wrap repairs
For non leaking damaged pipelines,
composite wrap repairs can be implemented with the pipeline in service preventing
the need to shutdown and vent gas from the pipeline
100%
Natural gas transmission
10
Portable
evacuation compressor for pipeline venting
This practice uses an in-line
portable compressor to remove gas and lower pipeline pressure before venting
72%
Natural gas transmission
11
Fuel
gas retrofit for blow down valve
Installing a connection to
fuel gas, the methane that is typically vented during a compressor blow down is
recovered to supplement fuel
33%
Natural gas transmission
12
Directed
inspection & maintenance at compressor stations
Conduct leak detection surveys
of facilities to identify and repair leak sources that are cost effective
13%
Natural gas processing and
transmission
13
Directed inspection &
maintenance at gate stations and surface facilities
Conduct leak detection surveys
of facilities and equipment to identify and repair leak sources
