IEA (2020), "Methane Tracker", IEA, Paris https://www.iea.org/reports/methane-tracker
Our analysis examines emissions sources along the full oil and natural gas value chains, except for any emissions that occur within industrial or residential buildings (on the basis that the abatement technologies and options for these end-use emissions are materially different than those for the value chain up to the end-use consumer).
For simplicity, the oil and gas sectors are divided into upstream and downstream segments. Upstream includes all emissions from production and gathering and processing; downstream includes emissions from refining, transmission and distribution.
The production subsector includes all onshore and offshore oil and gas facilities from either conventional or unconventional reservoirs. Liquefaction of natural gas, transportation either by pipeline or as liquefied natural gas (LNG) and regasification are included in downstream processes.
- Fugitive methane emissions occur from leakages that are not intended, for example because of a faulty seal or leaking valve.
- Vented methane emissions are the result of intentional releases, often for safety reasons, due to the design of the facility or equipment (e.g. pneumatic controllers) or operational requirements (e.g. venting a pipeline for inspection and maintenance).
- Incomplete flaring methane emissions can occur when natural gas that cannot be used or recovered economically is burned instead of being sold or vented. The vast majority of the natural gas is converted into CO2 and water, but some portion may not be combusted and is released as methane into the atmosphere.
The monetary value attached to captured methane is viewed from a global, societal perspective. Estimates of well-head prices are used in each country, with a credit obtained for selling the gas applied regardless of what contractual arrangements between different companies may be required to lead to this result.
Prices also assume that there are no domestic consumption subsidies as the gas could be sold on the international market at a greater price. The well-head gas prices used could therefore be substantially different from subsidised domestic gas prices.
Emissions levels and abatement potentials are based on sparse and sometimes conflicting data, and there is a wide divergence in estimated emissions at the global, regional and country levels.
The estimates shown represent our best understanding of emissions from oil and gas operations based on currently available data. They are designed to help governments and other stakeholders understand the magnitude of the issue, but given the uncertainty that exists, they are clearly not the last word. We aim to update these estimates as new and improved data become available. (See the World Energy Model documentation [PDF] for further information on how these estimates are produced)
As part of our ongoing efforts, we aim to include in the methane tracker all estimates from other groups, institutions or data sources of oil and gas-related methane emissions that can be directly compared with the estimates shown here.
We are in the process of compiling a database of audited or peer-reviewed estimates that provide country-level data on methane emissions from all oil and gas operations, or country-level estimates of emissions from the listed parts of the value chain, e.g. oil/gas upstream or downstream. These will be included here once this database has been assembled.
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While still a source of CO2 and methane emissions, flaring is preferable to direct venting of methane gas. Flares can be installed at oil and gas production sites, and components expected to emit methane can be routed to these devices. The “install flares” grouping in the IEA methane abatement cost curve includes installing portable flares to destroy methane emitted during discrete activities and routing methane that would otherwise be vented from certain equipment to existing flares.
Vapour recovery units (VRUs) are small compressors designed to capture emissions that build up in pieces of equipment across the oil and natural gas supply chain. For instance, VRUs can pull off gases that accumulate in oil storage tanks and are otherwise periodically vented to the atmosphere to prevent explosion.
Gas-driven pneumatic devices continuously release small amounts of gas, even when specified as "low-bleed." These devices can be replaced with "zero-bleed" technologies that use electrical power to operate, instead of pressurized natural gas. An electric motor can also replace a diesel or gas engine used onsite during drilling and completion.
The “replace with electric motor” grouping in the IEA methane abatement cost curve covers replacement of gas-powered devices with servo motors. “Replacing chemical injection pumps” is a separate category.
Leak detection and repair (LDAR) refers to the process of locating and repairing fugitive leaks. LDAR encompasses several techniques and equipment types. One common approach is the use of infrared cameras, which make methane leaks visible. LDAR can be applied across the supply chain. LDAR may be applied to upstream activities (including well development, gathering, processing) or downstream activities (such as transmission or distribution lines). LDAR is often required at particular intervals.
Pumps are used at well sites and across the oil and natural gas supply chain for a variety of purposes. Commonly, they are pneumatic pumps that use pressurized natural gas as a power source. These pumps vent natural gas in the ordinary course of business. Emissions can be eliminated by replacing the pumps to those that are powered by instrument air systems or electricity (powered by solar or other generators, or tied to the grid).
The “replace pumps” grouping in the IEA methane abatement cost curve include replacing Kimray/pneumatic or chemical injection pumps with electric pumps or solar electric pumps. Pneumatic pumps can also be replaced by instrument air systems; this technology is covered in a separate category.
Pumps and controllers are used at well sites and across the oil and natural gas supply chain for a variety of purposes. Commonly, they are pneumatic and use pressurized natural gas as a power source. These pumps vent natural gas in the ordinary course of business. They can be replaced by instrument air systems, which pressurize ambient air to perform the same functions without emitting methane.
Two kinds of compressors are used across the oil and natural gas supply chain to move product through the system: reciprocating and centrifugal.
The “replace compressor seal or rod” grouping in the IEA methane abatement cost curve include several activities related to both types of compressors:
Reciprocating compressors use piston rods to compress gas. Rod packing prevents gas from leaking around the rod. Compressor pressure, as well as wear and tear on packing parts and the rod can increase emissions. The older seals are, the more likely they are to emit. One technology, then, involves replacing rod packing systems to reduce emissions.
Centrifugal compressors use a spinning turbine to pressurize gas. Centrifugal compressors require seals on either end to prevent gases from escaping. Wet seals absorb oil and natural gas under pressure and can be a source of methane emissions. They must either be degassed, with the captured stream recycled into the compressor or used as fuel gas, or replaced with dry seals.
Gas blowdowns are conducted at wellheads or elsewhere along the supply chain when equipment (e.g. vessels, compressors) must be depressurized. Blowdowns can be triggered by emergency signals or routine start up or shut down procedures. When this happens, operators open up the well to remove the liquids and gas. Emissions are mitigated when excess gas is recovered and used on site or sent to the sales line, instead of being vented or flared.
Periodically over the life of a producing well, downhole liquids need to be removed to facilitate continued flow of product. Traditionally, a well operator opens the well and vents methane, relieving pressure and drawing liquids up through the wellbore. Plunger lifts may be installed to extract liquids more efficiently, while limiting the escape of methane. As pressure from accumulating fluids builds up, it pushes on the plunger. The plunger draws up gas and liquids in its wake. If a certain threshold of reservoir pressure is achieved through withdrawal of the plunger, gas can go directly to the sales line with no venting.
This catch-all category addresses other methane-reducing technologies or techniques that are not found on the IEA’s cost curve.
The “other” grouping currently includes:
Install new methane-reducing catalysts: Exhaust from gas-burning engines and turbines contains a methane from incomplete fuel combustion. Oxidation catalysts are used to reduce unburned emissions for other hydrocarbons; new catalysts are being developed to do the same for methane.
Deploy microturbines, mini-CNG, mini-GTL (gas to liquids), or mini-LNG facilities: Micro- technologies can offer capacity for compression or liquefaction of associated gas in remote locations. These technologies avoid venting and flaring by capturing gas for use at the facility, in the surrounding community, or for transport by truck or rail.
Conduct a pipeline pump-down before maintenance: A pipeline pump-down involves using compressors to lower pressure in gas lines before performing maintenance or repair. This technique avoids emissions that would otherwise occur as venting.
Conduct Reduced Emission or “Green” Completions: Reduced emission completions (RECs) are alternative practices that capture gas that would otherwise be released while completing or re-working existing wells. When the captured gas is delivered into the sales pipeline this reduces the need for flaring.