Potential energy

The reason we drill for oil and gas in the way that we do is, largely, because that’s how we’ve always done it. But as the more easily obtainable reserves begin to dwindle, the established techniques are becoming less useful.

When it becomes harder both to find and to extract fossil fuel reserves, how can current advances in engineering help to meet the demand for hydrocarbons and their products?

This is the question facing Geoff Maitland, professor of energy engineering at Imperial College London’s recently launched Energy Futures Laboratory (EFL). While the laboratory is looking at the whole spectrum of energyrelated research, Maitland is focused on the parts of the jigsaw concerned with fossil fuels, their exploitation and their transformation into useful products.

Imperial College is the sort of place that people find hard to leave behind and, like many of his colleagues, Maitland is on his second stint there. Starting out as a physical chemist, with a degree and doctorate from Oxford, he initially followed an academic path, working as an ICI-sponsored postdoc at Bristol University and transferring to Imperial as a chemical engineering lecturer until 1986.

His research centred around the links between the interactions of molecules and colloidal particles in fluids and the bulk properties of materials, and during his first stint at Imperial he specialised in polymer dynamics, rheology and design of chemical reactors.

He then decided to switch to the industrial track, working for oilfield technology company Schlumberger for 20 years. It was at Schlumberger that he began to specialise in fossil fuels, initiating research on characterising how drilling fluids, crude oils and multiphase mixtures flow.

This September Maitland brought his expertise — in the behaviour of the thermal and physical properties of fluids under extreme conditions, the activity of complex mixtures as they flow through the geology of oilfields and the various parts of the oil well, and the environmental impact of oil production — back to South Kensington to link up with the other scientists and engineers involved in the EFL.

‘Several universities, such as Stanford in the US and Heriot Watt in Edinburgh, have extremely strong energy research programmes,’ he said, ‘but what’s unique about what we have here is that we have world-class science and engineering across the board. The EFL is designed to link up all the strands of the research so that we can carry out multidisciplinary projects much more easily.’

Maitland thinks of his work as shedding the technological baggage of oil production. ‘The approach we have to take is to say, if we discovered fossil fuels now, what would we do? Given today’s environment, where, as well as producing power and fuels and the feedstocks for petrochemicals and plastics, we have to be mindful of the environmental viewpoint, can we be innovative using today’s technologies?’

Some of Maitland’s work has carried straight over from his time at Schlumberger, and this centres around the advanced control and instrumentation technologies used in the most up-to-date petrochemical plants within an oil well to improve its productivity.

Oil companies are increasingly using sensors to log the performance of their wells, but Maitland’s researchers are trying to take this concept one stage further.

‘One crucial factor is the advances in sensor technology, particularly in the scale of the sensors,’ he said. ‘We’re seeing the micronisation — and even, in future, the “nanoisation” — of sensors, and that enables you both to put them in difficult locations and to build in redundancy, so you can have plenty of sensors in place to cope with the harsh conditions.’

These sensors will monitor the flows of the oil, water or other fluids that are pumped into the rock reservoir to displace the hydrocarbon deposits. ‘The reservoir models are also becoming more sophisticated, linking the geology to the characterisation of the pore space, the fracture pathways and the fluid mechanics that support that,’ Maitland said.

Linking the sensor readings with the reservoir model will allow oil firms to understand which parts of the reservoir are currently producing oil, and which are becoming saturated with the injection fluids. A series of valves within the well would then allow sections without oil to be isolated, and the injection strategy changed to recover a larger volume of oil. 

This sort of capability is not far off, Maitland said, as most of the technology already exists. ‘The major challenge is in using a systems approach to integrate the information.’

Looking further into the future, however, Maitland believes that the way oil wells will operate will change dramatically. One problem with oil and gas exploration is that it’s wasteful, he explained.

‘Currently we take highpressure, high-temperature fluids from the reservoir and, with a lot of care, transport them several kilometres up to the surface, cooling them down and reducing the pressure. Only then do we start doing most of the separation and virtually all the processing of the fluids — which involves repressurisation and heating them up again.’

‘Then we use those kilometres of conduits just as transportation pathways, when what we have in principle is a high-temperature, high-pressure reactor system that’s currently empty. For example, we can do some of the catalytic processes we now do in refineries on the way to the surface.’

Developments in process intensification, where several of the functions of traditional large-scale chemical plants are combined in a single, much more compact piece of equipment, will help change oil wells into chemical plants where what emerges at the surface is a hierarchy of products tailored to the needs of society, Maitland said.

‘What you really want for the power sector is electricity, so ideally you’d have some down-hole generation. Then you’d want to produce a clean fuel, of which hydrogen would probably be preferred, but you could also make low-carbon fuels like methane or clean diesel. And you’d also make simple chemical feedstocks, such as olefines or methanol. Once the concept is established, you could play lots of tunes in terms of how you’d break the hydrocarbons down.’

This, said Maitland, will severely test the multidisciplinary capacity of the EFL. Key parts of the research will involve the design of new catalysts that can operate several kilometres below the sea bed, as well as chemical and systems engineering to integrate all the functions of this complex installation.

‘For the integrated production of fuel, power and chemicals, the way you’d control the plant to respond to the needs of the market — whether you’d have the same systems producing all three products, or some wells producing mainly fuels and so on — still has to be worked through.’

The applications needn’t stop with oil, Maitland said; in fact, they are likely to be more suited to nonconventional hydrocarbon reserves. Under-sea coal, for example, is difficult to mine; in situ gasification and processing installations could be a more practical alternative. And difficult hydrocarbons, such as oil shales and heavy oils, are prime candidates.

Currently these are barely exploited, because the oil is so hard to extract. ‘But if we had the alternative of saying we won’t produce the oil, but selectively process it and leave the low-value stuff in the ground, you overcome some of the process problems.’

It’s a long-term vision, Maitland admitted. ‘Some of this technology could find itself out there in 20–30 years time, but to realise the grand vision will take many decades. Hopefully it will be there at a point where utilisation of the fossil fuels that are left is absolutely crucial.’