Across the globe, vast quantities of natural gas sit trapped in the ground – discovered, but never developed. These are known as stranded gas wells, and until recently, most of this gas was simply flared or vented. Thanks to advances in cryogenic processing and modular small-scale liquefaction technology, this once-wasted resource is now becoming a commercially viable source of energy.
This article explores what stranded gas is, why it has historically gone unused, and how cryogenic gas recovery is changing the economics of remote and marginal gas reserves.
What Is a Stranded Gas Well?
A stranded gas well is one where natural gas has been discovered but cannot be economically or physically brought to market. Gas found alongside oil – known as “associated gas” – has traditionally been flared for exactly this reason.
There are generally two causes of economic stranding:
- Remoteness – the well is too far from any gas market to justify building a pipeline.
- Market saturation – the reserve sits in a region where local gas demand is already met, and exporting beyond that region is too costly.
These wells are often the first candidates for development once existing, more accessible gas fields begin to deplete.
With rising LNG demand and diversifying energy security needs, small-to-medium-scale LNG plants are increasingly being used to unlock gas from associated and remote reserves for distribution and vehicle fuel.
Why Flaring Is No Longer the Default Option
Flaring erodes the economic value of a well and is under growing regulatory and environmental pressure. For many new fields – particularly those in increasingly remote locations – flaring is simply no longer an acceptable option. This has driven a global push to find commercially and environmentally sound alternatives.
The Nature of Stranded Gas
Stranded gas is a combustible mixture of hydrocarbon gases, predominantly methane, but often including ethane, propane, butane, and pentane. Composition varies significantly from site to site, which is why detailed gas analysis is essential before any clean-up or liquefaction process can be designed.
Typical Composition of Stranded Gas
| Component | Typical Range |
|---|---|
| Methane | 70-90% |
| Ethane, Propane, Butane (combined) | 0-20% |
| Carbon dioxide | 0-13% |
| Oxygen | 0-0.2% |
| Nitrogen | 0-16% |
| Hydrogen sulphide | 0-5% |
| Rare gases | Trace |
Carbon dioxide, nitrogen, and oxygen must all be removed prior to liquefaction. With the exception of CO2, these gases are typically released rather than processed further. Meanwhile, the heavier hydrocarbon fractions – ethane, propane, and butane – can often be separated out and sold separately, adding an additional revenue stream to a project.
Choosing the Right Technology: CNG, LNG, or Power Generation?
There is no single “correct” way to exploit stranded gas. The right technology choice depends heavily on distance to market and the feasibility of transport:
- Nearby grid connection – if a grid connection is close by, on-site power generation is often the most sensible route, provided the economics stack up. Methane is relatively straightforward to use for power generation.
- Distances under roughly 100 km – compressing the gas to Compressed Natural Gas (CNG) for road transport may be viable.
- Longer distances – conversion to a liquid becomes necessary to increase storage density and reduce transport costs. This is where cryogenic Gas-to-Liquid (GTL) processing comes in.
A typical installation producing just 20 to 40 tonnes per day of methane can still be commercially viable – and 20 tonnes per day alone can generate approximately 4.5 MW of electricity.
How Cryogenic Gas Recovery Works
Cryogenic separation cools stranded gas to extremely low temperatures, cleaning it up and splitting it into its various fractions before finally producing liquid methane. The by-products – various hydrocarbon fractions – can then be transported separately for commercial sale.
Core Process Components
A typical cryogenic liquefaction system, built around either a single-mixed refrigerant process or a propane pre-cooled single-mixed refrigerant process, includes:
- Cold Box(es) – containing brazed aluminium heat exchangers, separator vessels, cryogenic piping, instrumentation, and valves (propane pre-cooled systems may also use core-in-kettle heat exchangers)
- Mixed Refrigerant Compressor – either electric motor or gas turbine driven, depending on site requirements
- Refrigerant System Vessels – fitted on compressor suction and discharge
- Aerial Inter-Coolers and Condensers – to remove waste heat from the process
- Cryogenic Liquid Collection and Vaporiser System – to convert stranded gas into liquid form for off-site transport
- Heavies Removal Column – included where feed gas composition requires it
The choice between process options is driven by a detailed analysis of capital versus operating costs for the specific site.
Why Small-Scale Liquefaction Makes Sense
Small-scale LNG plants offer a distinct advantage: their compact footprint allows LNG to be produced close to where it will actually be used, cutting transportation and product costs for consumers. This also enables:
- Localised peak-shaving – balancing gas supply during periods of high and low demand
- Off-grid distribution – allowing communities without pipeline access to receive gas via stored LNG
Interestingly, industry cost trends haven’t followed a simple downward curve. Construction costs for green-field LNG projects actually began climbing from 2004 onward, driven by limited availability of EPC contractors (amid a global surge in petroleum projects), rising raw material costs such as steel, and a shortage of skilled technical operators. Since then, the broader spread of cryogenic know-how into developing regions has helped moderate prices again, making small-scale applications commercially attractive once more.
Safety, Environment, and Transportation
Safety
Natural gas is combustible, but in its liquid state, LNG is neither explosive nor able to burn. For ignition to occur, LNG must first vaporise and mix with air within its flammable range of 5% to 15%. International safety standards govern every stage of design, construction, and operation of LNG facilities, and adherence to ISO-recognised quality systems is essential throughout.
LNG tankers have sailed over 100 million miles without a shipboard death or major accident – a strong safety record for the industry as a whole.
Environmental Benefits
As the cleanest of the fossil fuels, natural gas helps reduce harmful atmospheric emissions when used in place of dirtier alternatives. The growing use of Compressed Natural Gas (CNG) as a vehicle fuel is already helping cut urban traffic pollution in cities worldwide, and unlocking stranded gas reserves supports this broader shift toward cleaner fuels.
Transportation
Liquid methane is typically transported by trailer-mounted road vessels, or via ISO frame containers where the route spans road, rail, and sea. It is stored at approximately -160°C, at pressures up to 20 atmospheres. Because LNG has an energy density 2.4 times that of CNG (and around 60% that of diesel), it remains cost-effective to transport over long distances where pipelines don’t exist. Well-insulated vessels typically limit heat-ingress losses to as little as 0.5% per day.
The Project Route: From Discovery to Operation
Developing a stranded gas resource follows a structured path:
- Identification of a possible stranded gas resource
- Desk study to evaluate available geological data
- Estimation of methane quantities
- Field study to determine factors affecting viability
- Final system specification and design
- Procurement of component parts
- Construction and commissioning
- Ongoing operation and maintenance
A specialist partner is typically involved from the earliest identification of an opportunity – analysing borehole logs and local geology to estimate reservoir size, then building a financial model covering installation costs, operating costs, and expected project revenue. Only with this data can long-term project viability be properly tested before moving into technical design, procurement, build, and commissioning.
Key Takeaways
- Stranded gas wells hold significant untapped energy value, previously lost to flaring due to remoteness or market saturation.
- Even modest volumes – as little as 20-40 tonnes per day of methane – can be commercially viable, with 20 tonnes/day capable of generating roughly 4.5 MW of electricity.
- Technology choice (power generation, CNG, or LNG) depends primarily on distance to market.
- Cryogenic separation and liquefaction allows clean-up, fractionation, and conversion of stranded gas into transportable LNG, with valuable hydrocarbon by-products.
- Robust safety standards and proven transport methods make LNG a well-established, low-risk way to move stranded gas to market.
Get In Touch
If you’re evaluating a stranded gas resource and want to understand whether cryogenic recovery could make it commercially viable, our team can guide you through everything from initial geological assessment to full turnkey design, construction, and operation. Contact us today to discuss your project and take the first step toward turning a stranded asset into a valuable energy resource.