Onshore gas plant - Management of energy performance

Energetics assisted the operator of an onshore gas plant to identify a range of energy saving and Greenhouse gas (GHG) abatement opportunities. Despite the large demand for gas by the compressor and generator turbines, the study showed that the largest point source of GHG emissions was the methane remaining in nitrogen vented from a nitrogen rejection unit. Technologies borrowed from coal mining may offer a means of reducing emissions from this source.

Key Facts

Client: Onshore gas plant
Location: Western Australia
Industry: Oil and gas
Project: Management of energy performance
Lead consultant:

 

Outcomes

Understanding the energy and GHG footprint

Through the use of its robust analytical tools, Energetics was able to quantify the major energy users and sources of GHG emissions. We showed that the largest contributor to the GHG footprint was vented methane. Our custom Energy-Mass Balance (EMB) tool provided the site with its first view of energy demand across all its operations.

Establishing the priority GHG abatement opportunities

Using the EMB tool to build the analysis of energy use and GHG emissions, a range of abatement opportunities were found. Excluding the gas turbines, cost effective energy savings amounted to 5% of total energy use. The single largest source of energy waste was poor gas turbine operation primarily due to under-loading of turbines. Larger savings could be obtained by altering the operation of the gas turbines but this required a comprehensive risk analysis to explore the likely impact of reductions in spinning reserve.

GHG reductions amounted to 20% of emissions and relied on technologies to oxidise methane in Nitrogen Rejection Unit vent gas.

Strengthening GHG reporting

The site had a range of obligations to report energy use and GHG emissions. Utilising our deep knowledge of the regulation and processes associated with GHG inventory reporting, Energetics provided practical advice on the necessary improvements to metering and monitoring needed to achieve the target accuracy for GHG inventories.

Background

The operator of an onshore gas plant sought to assess the energy performance of its assets in line with its corporate requirements. This included the development of an Energy & GHG Management Plan to identify emissions sources and options to reduce emissions.

Energetics undertook this assessment to identify initiatives and implement processes that would ensure energy efficiency and energy source substitution opportunities were integrated into the business. The focus of the assessment was the compilation of an energy baseline, and the analysis of likely areas for improvement.

Comprehensive analysis of energy use

Energetics has a range of custom tools developed for upstream oil and gas production, which allows us to quickly develop energy baselines, identify improvement opportunities and quantify savings.

The analysis of the site began with the development of an EMB. As occurs at many gas plants, the metering of fuel gas beyond the main fuel gas meter was very limited. Energetics has a range of tools that were applied to validate the indicated flow of fuel gas to the turbines and to the other gas users (thermal oxidiser, glycol strippers, MDEA regenerator). The goal was to obtain closure of the fuel gas balance to ±5%. Our analysis highlighted performance issues with the gas turbines. The major issue was under-loading of its large compressors. In addition, the site was advised to assess its cleaning regime.

Robust identification of opportunities

Energetics reviewed the site’s energy baseline, which highlighted areas where energy was used inefficiently. Energetics used a process not unlike a hazard and operability study (HAZOP). We systematically reviewed the process flow diagram to identify opportunities for better heat integration or the utilisation of waste heat. For instance, the study highlighted an opportunity to use surplus heat in the heating medium circuit to preheat air to the thermal oxidiser.

We also assessed the site’s approach to energy management using our One2Five® tool which evaluates key management processes and systems on a 1-5 scale of maturity. This highlighted a number of areas for improvement relating to measurement, KPIs and targets.

Challenges - the myth of free energy

In common with many similar facilities, there was a view at the site that gas was effectively free. This view failed to account for the opportunity cost of additional product sales, the royalty charges payable to the Government and in the future, costs due to GHG emissions.

Calculating the opportunity cost of fuel gas can be complex. Energetics helps to simplify this for clients by using a variety of approaches and tools that we have successfully applied to a range of different clients and facilities.