Quantitative multi-species hydrocarbon metrology in gas pipelines -- enhancing commercialization potential by extension to new laser wavelengths

SUMMARY OF THE ORIGINAL PROJECT:
Accurately monitoring the composition and flow-rate of natural gas from a petroleum reservoir is critical for extraction companies to quantify the productivity of their oil and gas fields. Our new project "Quantitative multi-species hydrocarbon metrology in gas pipelines" (ST/T000635/1) identified an opportunity for a first-to-market system integrating broadband, high-resolution mid-infrared spectroscopy into a conventional gas-flow meter. The project is supported by >£400K direct and in-kind contributions from industrial partners GM Flow Ltd. (a leader in dry-gas metering) and Chromacity Ltd. (a tunable laser manufacturer), and seeks to use fibre-delivered light from a pre-existing 3 - 4um laser to quantify the abundance of gaseous alkanes carried in pipelines from the production reservoir.

The project methodology exploits high-resolution Fourier-transform laser spectroscopy and an innovative baseline-extraction algorithm, both emerging from an earlier STFC project (ST/P00699X/1), which resulted in a recent patent application and journal paper. Broadband mid-IR light is modulated by a scanning Michelson interferometer functioning as a high-resolution Fourier-transform spectrometer. This light is then fibre-coupled and used to interrogate gas sampled into a metrology cell at a flow meter. Our unique algorithm is used to extract the concentrations of the multiple gas species present.

Heriot-Watt will manage the project and take responsibility for the hardware and software development associated with the multi-species gas spectrometer, and will collaborate with three partners as follows:
* GM Flow manufacture flow meters for the "dry gas" market, and will engineer an integrated module that uniquely allows in-situ gas composition sampling and spectroscopy at the flow meter.
* Chromacity, a HWU spin-out manufacturing near- to mid-IR femtosecond lasers, will lead the system integration of the laser, spectrometer, delivery-fibre, gas flow meter and software.
* Southampton University will provide new "airguided" mid-IR fibres, complementing commercially available solid-core fibres and potentially offering superior long-range transmission characteristics.

SUMMARY OF THE PROPOSED CAPITAL EQUIPMENT AND THE ADDED VALUE IT WILL PROVIDE:
Our request to STFC is for 65% funding of a variant of a Chromacity Spark-OPO, providing broadband coverage across the 2.4-3.1-um region. Co-funding of 25% from Heriot-Watt and 10% from Chromacity has been secured. A formal quotation is provided.

Our original project proposal anticipated re-purposing a 3-4-um broadband laser purchased for an earlier STFC project in atmospheric spectroscopy, where the weak ambient concentrations (e.g. 1.8 ppm CH4) require wavelengths aligned to the strongest molecular cross-sections. While the IPS project could proceed with this laser, there are considerable benefits from replacing the previously earmarked laser with the proposed shorter-wavelength source, namely:

a. Avoiding line saturation, due to the 100x lower cross-sections, thus improving measurement accuracy.

b. Improving species distinguishability, due to lower spectral interference, again improving accuracy.

c. Extending sensitivity to other important species, due to the presence of absorptions for H2S and CO2.

d. The added commercial value introduced by these new features, including higher confidence in the concentration data,
monitoring of safety critical and highly toxic H2S, and monitoring of reservoir quality through the CO2 information.

e. The acceleration of lab research enabled by having a dedicated laser source for the project, rather than one shared with another grant.

In summary, moving to this wavelength band would now allow ALL of the main components of natural gas to be analysed, with the exception of N2 (a non-infrared active gas presnt at <5% concentration).