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Finding more hydrocarbons with better seismic

Monday, August 8, 2022

With Russian gas being taken off the market, the world is looking for ways to find more hydrocarbons and get it into production. Neil Hodgson suggested ways that this can be done with modern seismic data

Russian gas imports to Europe had been gradually growing from 447 billion cubic metres (BCM) a year in 2010 to 639 BCM in 2020. They had been predicted to grow to 715 BCM in 2030.

But due to the Ukraine invasion, 'that will never happen,' said Neil Hodgson, VP geoscience with Searcher Seismic, and a former exploration manager with Matra Petroleum, Premier Oil and GB Group.

He was speaking at a webinar organised by Finding Petroleum on Mar 25.

'Europe's got a problem. Where is [its energy] going to come from?'

'Because Russia invaded Ukraine, we want to point out that attacking another sovereign country is not a good idea. One way you can apply pressure is through economics, and you can't do that if you get gas from Russia.'

Many of the pipelines carrying Russian oil and gas go through Ukraine, as he showed on a map. 'If anybody is wondering why this war in Ukraine is happening, perhaps this image has something to do with that.'

There are pipelines from North Africa into Europe, but can only increase throughput a 'a limited amount.' Gas can be sent by ship as LNG, which is expensive and has been increasing in price over the last year.

Meanwhile, over the last 2 years, the oil price has been steadily increasing, as the world's economy rebounds from Covid, from $60 up to $100. But there has not been much new exploration.

'For the last 5 or 6 years there's been a feeling that the oil and gas [industry] has been toxic as a place to invest. You couldn't get any money to drill an exploration well.'

After the Russian invasion of Ukraine, the oil price shot up further, and was $118 at the time of the webinar, due to concerns about restrictions of supply.

This means that the commerciality of oil and gas projects looks very favourable in terms of dollar returns per barrel.

'The reality that we find ourselves in today, we've handed our energy security to Russia without thinking about it. That was not a brilliant idea. We've also woken up to the fact that without that gas we would be pretty screwed for energy in Europe. We still have a carbon economy.
That's a different message to the one we've been getting that says, 'a lot of our energy comes from windmills.''

So today, there is an increasing realisation that investing in oil and gas is not immoral - but companies are looking for oil and gas opportunities which are advantaged in some way - such as by being 'easy to find, easy to develop, and easy to monetise,' he said.

'By easy, I mean quick. In the [recent] past if you had an oil project, you'd try to get that in production in 7 years. When I came into the industry, a gas project would come into production in 10 years. You'd want to halve that now.'



Mature basins

Mature or 'over mature' basins are a good place to start looking for advantaged resources. 'You know what's happening to the geology, you've got a good understanding of the subsurface, you can get hold of seismic data and improve it. Our ability to improve seismic data is amazing compared to 10 years ago.'

In a mature basin, any new discovery is likely to be next to infrastructure, which means you don't need to do so much building. You have a pipeline system you can connect into. 'You've usually got a sophisticated regulator, who understands what you've got to do and will help you do it.'

But on the other hand, a mature basin 'almost by definition' has already been thoroughly explored. For example, the UK's Southern North Sea has been explored since the 1960s.

But there may be new tricks you can use to find hydrocarbons which previous exploration efforts did not find - using new developments in seismic processing.

For example, it was impossible to gather good seismic data beneath salt domes until about 15 years ago.

Looking at a map of existing gas discoveries in the UK Southern North Sea, a very mature basin, and a map of where the salt diapirs (domes) are, there is no correlation between them. It shows there hasn't been any exploration beneath salt diapirs, he said.

The only gas fields beneath salt domes are fields which were discovered when exploring adjacent to the salt dome, and then it was found that the field extended to below the salt dome.

A geologist would expect a salt dome could be particularly good place to look for hydrocarbons, because they can trap gas generated from Permian or carboniferous organic material. Also, a salt dome could form over the crest of a fault block, he said.

Exploring below salt domes today doesn't necessarily require new seismic data, you can take the old seismic data and put it through modern data processing techniques, he said. Most Southern North Sea data was last processed 15 years ago, some of it over 20 years ago.

'I guarantee that when we reprocess the data it will 'light up' with hydrocarbons,' he said.

Another example of how seismic can help with exploration was given for fields offshore Nova Scotia (East Canada). This region can be classified as 'over mature'. Production finished around 2017 and fields have been decommissioned, although a lot of the equipment is still in situ, he said.

Using modern seismic data processing techniques, 'we found there's 1.5 TCF of gas never developed in that area, it is just sitting next to infrastructure but not being developed,' he said. 'Nobody is exploring Nova Scotia offshore anymore.'

Mr Hodgson showed an example of Nova Scotia seismic data from 1998 which had been used to find the reservoirs. By today's standards, 'it looks awful, you can just about see the top of the sedimentary sequence, you can't see much in it. In the past they determined where fault blocks are and tried to drill fault blocks.'

'They developed the fields on this standard of seismic. Just think how much more gas we could find in that area if we had better data.'

'You have to look at the latest quality seismic data before you can convince yourself that it is a truly depleted basin. You might think a basin is exhausted when you've produced all the hydrocarbons, but it is only the geologists that are exhausted. If you give them new seismic data, you revitalise their imaginations.'




Frontier basins

If you are looking in frontier basins, hydrocarbons will be most advantaged if you find a very big field, because the amount of overall production for each dollar of investment will be greater.

For example, Guyana in South America. This is also an example of a rapid development, with first production coming online just 4 years after the Liza discovery. The field is expected to provide 'a couple of billion barrels of oil.'

'Even the downside cases of the modelling are pretty big,' he said. This means, 'you can make an investment decision to develop the field pretty confidently.'

Crossing the Atlantic to offshore Namibia, the Venus discovery, recently made by Total, is also very big, about 3bn barrels of light oil. Its 'next door neighbour' Graff is also a large discovery. Although it is in 3000m water depths, the benefits of the hydrocarbons outweigh concerns about the complexity.

'A lot of revenue from that will go to the government of Namibia. They will be able to do really great things for the people of Namibia.'

On the modern seismic, you can pick out the source rock, which is feeding oil up to the two reservoirs which make up the Graf discovery.

'I was still being told there wasn't a source rock south of Walvis Ridge until half way through last year,' he said. (The Walvis Ridge is an ocean ridge which hits land near the North Coast of Namibia / border with Angola).

'Now it's proven and it's generating enough oil to charge this 3bn barrel prospect Venus.'

If South Africa wishes to develop oil production, it has 'the possibility of this play extending to South Africa.'

'There will be plenty of other discoveries in Namibia on the back of this.'

To drill in 3000m water depth was unimaginable about 15 years ago; in 2012, the world's deepest well was 3100m offshore India, he said. By 2016, the record was the 3400m Raya well (Uruguay) drilled by Total. By the end of 2021, Total made a new record, the 3628m Ondjaba Well offshore Angola. So, the trend is clear.

The largest prospects may be under over 4000m of water - which we may be comfortable drilling by 2026, he said.

The geological knowledge from West Africa can also be used to explore on the East Coast of South America, around Uruguay, southern Brazil and Northern Argentina. Seismic lines from both sides can be fitted together.
'We see exactly the same geology, the same Aptian source rock, the same basin floor fans stacked on top of them,' he said.

So, the Venus discovery has also 'opened up the South American play'.



India, Eastern Med, Canada

In India, 'a lot of seismic data has been acquired (but) not particularly good quality,' he said.

There have been limited discoveries. Some areas have been explored only in 'relatively shallow' water, but never explored in deepwater. But the plays do look similar to what has been seen offshore Uruguay and Brazil where big discoveries have been made.

'When you re-process the seismic, as we've done over the past year, the geology just leaps out. All these margins in East India have become incredibly prospective. Explorers have never had this quality of data to explore with.'

The Eastern Med is interesting because, although it is a frontier basin, it is possible to connect new fields with existing infrastructure. For example, The Tamar gas discovery in the Eastern Mediterranean (offshore Israel), discovered in 2009 and in 1500m water, was brought onstream in 3 years, despite there being only a very small gas market in Israel.

The Zohr discovery in Egypt was developed in about 2.5 years. The initial plan was to tie it back to infrastructure on the Israeli shelf, but ultimately it was tied back to Port Said on the Egyptian coast, 190km.

In Nova Scotia, there may be many gas fields to discover. The Aspy-1 well, a 'brilliantly brave' well drilled by BP in 2018 beneath a salt canopy, did prove a hydrocarbon system, although it wasn't a big discovery.

It is 'quite possible' if not 'probable' that any discoveries will be gas rather than oil, because the source rock is deep enough to be in the gas window.

But this may make it easier because there is an existing gas field and infrastructure nearby, close to Sable Island, he said.



Seismic

The secret to success in all these cases is seismic - either getting good, new seismic data, or getting your existing seismic in good condition, with recent advances in processing.

When it comes to acquiring data, consider that 20 years ago, 3D seismic streamers were normally 4km long, with 8 attached to a vessel. now they are normally 8km long, with up to 24 streamers behind one vessel. 'That gives you a much better result when you process it,' he said.

Seismic vessels often survey today in multiple azimuths (directions), such as going East to West as well as North to South.

The costs of acquisition and processing can be 10x higher than before. But if it identifies targets which are worth drilling, then this cost is worth paying.

The modern data can be used to supplement the existing data, not just replace it.

Modern processing techniques can do more with more complex structures, such as steep dip.

Land seismic surveying techniques are also improving, and there is more room for further improvement, he said.

'The amount of onshore 3D seismic [ever acquired] is relatively small compared to the amount of 3D seismic we have offshore now,' he said. But this can mean, 'the room for making huge leaps forward with your understanding onshore is much greater than it is offshore, by acquiring new, relatively cheap, 3D surveys.'



People

Mr Hodgson was asked whether we still have enough people capable of understanding seismic data and geology to do exploration.

He replied that if the industry has a low attractiveness to graduates, it could be blamed on society's toxic view of the industry.

But on the other hand, oil and gas exploration does not need as many people as it used to. Individual exploration staff can monitor a much larger area today than they used to be, and calculations can be done much more quickly.

And the industry still has 'absolutely brilliant geoscientists,' he said.
'I've got a lot of confidence we do have the people to do this exploration. It's a case of letting them follow their ideas.'

Geoscientists around the world increasingly come from the country which owns the reserves, he said. 'When I worked in Egypt for British Gas in the 1990s, all the papers written about the Nile Delta were written by expats [Westerners]. Now they are all written by Egyptians. I think that's exactly how it should be.'

You can watch the webinar here









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» Premier Oil Plc


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