Up and away

Complementing seismic exploration is crucial to keep costs down. Phill Houghton sat down with Oil&Gas to explain how cutting edge airborne gravity gradiometry techniques can help reveal hidden depths.

O&G. How applicable are airborne gravity gradiometry surveying technologies for oil and gas exploration?
PH. Predominantly the oil and gas sector is looking for detailed, subsurface information that can help drive their exploration. The industry's primary method for this is seismic; it's the technique that is used more than any other. However, it's not always easy to acquire in difficult terrain or remote locations where it can be cost prohibitive.

Gradiometry is a relatively new technique that can provide the industry with good geologic information and subsurface imaging all from the air. The resultant information, which is also complementary to seismic, can then used to better understand the subsurface and reduce overall exploration risk.

O&G. So in expensive or remote locations for seismic you might use gradiometry first to identify the most promising spots before you did a full seismic scan?
PH. That's certainly an option for areas where access is difficult – like the Arctic – where you have environmental issues and a limited weather window to acquire data. Flying a gradiometry survey enables you to rapidly screen areas and use the data to help focus your seismic acquisition.

Another area is where you have sparse seismic coverage and limited geologic information or gaps in your data. Here you fly the gradiometry survey and use the detailed information acquired to enhance the seismic interpretation, resulting in a more complete geologic picture.

O&G. Gradiometry is a step forward from traditional gravity systems – what are the limitations of these more conventional approaches?
PH. The big problem with conventional gravity systems is that they have a limited bandwidth and lower resolution when deployed in a high dynamic environment. If you could have a traditional system with infinite bandwidth and excellent signal to noise, gradiometry would not be as valuable. However this is not the case for conventional instrumentation and becomes a physics problem rather than a geology issue.

Gradiometry is not a new technique and has been around since the early 1900’s. During the cold war the technology was further developed by the military sector, but it only became commercially available in the 1990's. These latest systems are basically adaptations of military systems for use in the oil and gas industry.

Conventional gravity is still useful, particularly in basin scale exploration where you're looking at the bigger picture. However, while the explorationist wants the bigger picture; he also wants the detailed picture too. This is simply not possible with traditional methods; you have to go to the next generation of systems, the gravity gradiometer. It is not a blackbox; it is a proven technology with new methodologies employed to extract the benefits of the significantly improved measurement.

O&G So if this technology is relatively new in terms of commercial exploitation, how is it going to develop and facilitate better functionality in exploration?
PH. I think the industry will continue to push seismic technology further; however, people are beginning to realize you can augment or integrate other complementary data sets with the technique to help deliver a better result. I think we will see continued development in this area – it is no longer about one technique being applicable for exploration. This of course, opens up many new challenges; new algorithms have to be developed, new software coded and new workflow strategies defined. These are all things we are currently working on.

The aim is to collect data using a multi-disciplinary approach, which when fully integrated delivers an improved understanding of the sub surface geology. On the plane, we don't just acquire gravity gradient data. We also acquire magnetic gradient data and LIDAR data. All of the data is used to derive an integrated picture of the subsurface. If you're looking for a drillable prospect, the combined information gives you greater confidence, reduces risk, and increases your probability of success.

A future area of development will be in the core technology used. Although rooted in the military, the existing technology is basically 25 years old. The system we currently fly took an estimated $250 million to develop back in the 70’s – so at today's prices it requires a significant investment to replace it.

With the help of our investors we are now developing the next generation of instrumentation, largely using superconducting techniques. The next generation of gradiometers will be even more sensitive than the ones we're flying today and that equates to even better geologic resolution.

O&G. Can you quantify the return on investment from this kind of technology? What does that increased probability of drilling success equate to in exploration costs?
PH. Understanding return on investment, economic value analysis or value of information is crucial for any new technology. However, as a service provider you may not have all the information available to you on the true costs of exploration. In some cases we will be able to directly attribute gradiometry to exploration success; in others, it'll be very difficult to pinpoint the key success factor, especially if a multi-disciplinary approach is used. Different companies use different methods to measure a return on capital employed and more work is needed in this field.

The technique is still very young and our projects to date have not yet gone full cycle – we have been flying commercially since 2005, and newly discovered fields generally don’t come on stream for three to five years. So can we claim a direct return on investment at this stage? Probably not. Have we had technical successes? Absolutely.

We do have some generic economic value analysis tools that we use, but often the benefits are easy to calculate. For example, if you wanted to explore in the foothills of British Columbia, where seismic costs are circa $100,000 per square kilometer and your area of interest is 1000 square kilometers. Your exploration budget needs to be $100 million for seismic alone. Using gradiometry to acquire detailed geologic information so that the area can be
‘right sized’ to 300 square kilometers of detailed seismic saves you $70 million less the cost of the survey. A clear economic benefit.

For some companies it's all about timing. Going from initial exploration to first production is crucial, especially when commodity prices are high. So any technique that can accelerate your time to market is going to be valuable to you. This is another area where gradiometry can assist.

The key thing to understand is that gradiometry is a complementary technique to traditional methods. The crucial factor is how you use the data, and I think in the past, the software, the processing algorithms, and the interpretation workflows weren't available. The tools to fully exploit the data are now here and as the technology becomes more accepted it will become more valuable. The next force in exploration has finally arrived.

Phill Houghton is VP Sales and a co-founder of ARKeX. He has worldwide oil industry experience with more than 25 years in sales, technical development and gravity surveying gained with ARK Geophysics, MGAL, Oceonics, and the Royal Navy Hydrographic and Oceanographic Office. He is an electrical engineer by training.