The fuel gas challenge

With gas prices at historical highs, and increased attention being paid to greenhouse gas emissions, operators need to understand the magnitude of fuel gas consumption within their own facilities. Action needs to be taken to optimise processes, conserve energy and reduce emissions.

Extent of the opportunity

Annually an estimated US $10 billion in fuel gas is used in upstream oil and gas processing plants in the Middle East.

Integrated energy audits of 18 plants in Canada and the US found that with improved energy efficiencies, 15 to 20% of the fuel gas could be saved and sold. In some regions this could very well be higher, due to the differing levels of maturity of facilities and reserves. On this basis, a potential saving of more than US $1.5 billion a year could be made in Middle East facilities through improved operating practices and better technology.

It has been noted that fuel gas consumption increases with time, due to maturing gas fields needing additional compression to deal with declining reservoir pressures. Further, the changing composition of the gas, and declining throughput, brings about inherent inefficiencies and the use of relatively more fuel gas.

Driving force

Energy efficiency in the production of natural gas not only makes good financial sense, but is part of the conservation equation for managing a limited resource. It has the potential to be a large part of any plan to reduce greenhouse gas emissions and meet emissions control demands, stemming from initiatives such as the Kyoto Protocol.

How much fuel gas should it take to produce one unit of sales gas? For many processors of natural gas, this question has never been considered and there is no consensus as to what constitutes a practical and reasonable fuel intensity. Establishing such a target will result in steps being taken to ensure responsible stewardship and more accountability for the fuel gas used.

The fuel gas challenge in the Middle East is significant and corporations will take an aggressive response because of the extremely attractive financial pay back. Managers at the highest corporate levels need to take responsibility for this fuel gas challenge, encouraging more responsible fuel gas usage in their facilities.

Methodology

There are four parts to the effective application of this optimisation procedure: an integrated energy audit, process modelling and optimisation, performance bench marking and application of innovative technologies.

All gas-processing facilities comprise a series of inter-dependent process units – it is this inter-dependence that often leads to real fuel saving opportunities.
A multi-disciplinary team consisting of as many as eight experts, each with expertise in a relevant unit process within the plant is assembled. The team is set the task of optimising each of the individual unit operations and determining how they should be operated to maximise the efficiency of the entire operation. It was this integrated approach that resulted in the very positive results at each plant.

Not only were the ‘low-hanging fruit’ opportunities in each individual unit identified, but more importantly, opportunities reaching much further across the plant, allowed the energy flows between units to be identified and optimised.

During the course of this programme it became evident that many of the same type of opportunities existed in all of the plants. This led to the generation of a number of process optimisation models, covering each of the units in question. These models could then be applied to other plants, to identify units that were operating outside the recommended optimised conditions.

Plotting the energy flows for all of these optimised units together highlighted additional opportunities. These were centered on the possibility of integrating energy generation and consumption, thereby offering the opportunity for balancing and optimisation.

In many facilities considerable effort has already been expended, both by in-house study and by outside consultants, in optimising the plant. For many the belief is that there is little or no room left to squeeze additional energy savings. This audit approach has demonstrated the opposite. New energy efficient and environmentally-friendly technologies were also identified that could fit in the optimisation process. The application of these is an ongoing programme.

In order to validate technology claims and to convince industry of the value of such technologies, field demonstrations of these new technologies, designed to achieve higher efficiencies and better environmental performance, were undertaken to promote their uptake and show new ways to achieve fuel gas savings. The demonstration projects also provided useful and necessary information on the capital cost and likely pay out times.

Results and conclusions

Energy consumption associated with the processing of raw natural gas and refining of crude oil has real value and must be measured and properly accounted for. The measurement of this fuel gas can result in identification of opportunities to conserve energy, at the same time realising significant reductions in greenhouse gas emissions from these facilities.

The results of the energy audit programme are significant, both in energy-savings and environmentally. Measurement leads to responsible use and optimum savings result from integration. Fuel gas savings are in the order of 15 to 20% and come with associated greenhouse gas reductions of approximately 20%.