Offshore liquids stripping facility - Greenhouse emissions modelling

Energetics assisted the developer of an offshore liquids stripping facility to develop a greenhouse gas (GHG) emissions model based on design data. This allowed the developer to appreciate its potential exposure to emissions trading or a carbon tax. The work also identified opportunities to reduce GHG emissions from the facility prior to the design being finalised for construction.

Key Facts

Client: Offshore liquids stripping facility
Location: Western Australia
Industry: Oil and gas
Project: Greenhouse emissions modelling
Lead consultant:

 

Outcomes

Predicted Greenhouse gas footprint

Based on the design of the liquids facility, the GHG emissions were estimated to exceed 500,000 t CO2-e per year under normal operating conditions. The largest individual sources of emissions contributing to this footprint of the facility included the two main gas compressors (52% combined) and the three gas turbine generators (26% combined). Importantly, fugitive emissions contributed 13% to the total emissions.

Establishing the priority GHG abatement opportunities

The results of this GHG assessment facilitated the focussed analysis of opportunities to reduce the GHG emissions footprint of the liquids facility, thereby reducing liability under a potential emissions trading scheme to be introduced in Australia. Several opportunities to reduce the GHG footprint were noted through the course of the work and it laid the foundation for improvements at the design stage.

Preparing for NGER

The company was exposed to the processes required to comply with NGER. Energetics recommended a structured NGER Gap Analysis. A thorough NGER Gap Analysis would also identify the required metering and monitoring requirements to meet compliance and ensure that this information was available for inclusion in the design.

Background

The developer of an offshore liquids stripping facility was keen to assess the total GHG emissions from the proposed facility. An earlier assessment of the potential emissions had been performed but the company was seeking a more rigorous approach in line with internationally-accepted guidelines.

In addition, the company wished to understand and assess options that may lead to the reduction of this emissions footprint. The final design of the liquids FPSO facility was soon to be completed and the company wanted the GHG mitigation options to be assessed before the design was determined.

Project objectives

This project was commissioned by the company to assist in assessing the total GHG emissions from a proposed liquids stripping FPSO facility. The scope of the GHG assessment included an understanding of emissions associated with:

  • the installation of the facility (sea transport and ship movement associated with construction)
  • the first year of operation, as the production output ramped up to the expected annual capacity
  • steady–state operation, where the production output reached the expected annual capacity

The GHG assessment included emissions from all sources including venting, flaring, fugitive and combustion emissions. Current design data was used as the basis of the estimate.

Internationally recognised approach

This GHG assessment was conducted in accordance with the guidelines provided in the API Compendium, utilising the publically-available SANGEATM software platform for data entry, calculation and storage. Data for the assessment was derived from the design models of the facility plus established industry factors. Any assumptions were derived from workshops with company representatives, internal documentation describing the design and specifications of the facility and publically available documentation and specifications of similar equipment.

Challenges

Fugitive emissions were calculated using a facility-level approach. This is a coarse method for estimating the fugitive emissions and a more refined approach, based on individual fugitive emissions sources, was recommended.