4D Book of Knowledge Chapter 2 – The role of 4D in the coming decade? DIGITAL 4D as Standard (by Prof. Colin MacBeth)
Predicting the future of 4D from its past
4D or time-lapse seismic is now one of the up and coming technologies in the industry today .. proven, mature and accepted. This technology was famously resisted by several major oil companies in the late 1980’s as not being economically viable, flipped overnight to become the gold standard in production monitoring for many major companies across many of the world’s basins. It has opened up the door to informed surveillance of reservoirs during production, IOR and EOR, and impacts positively on NPV. So what does the future have in store for this technology that has already achieved significant success and has such a strong track-record?
The future, of course, is never easy to predict – indeed who could have predicted our current oil price! But the safest approach is to understand the past and make reasonable extrapolations of technology advances based on their cyclical lifetime, whilst at the same time, taking note of the game-changing ideas in the pipeline. With this in mind, let us quickly remind ourselves of how much has changed in just over a few decades: from legacy 4D, dedicated 4D, reduced cost towed streamers, multi-azimuth shooting, permanent seabed sensors, increased frequency and reduced periods of shooting (1 or 2 years or even as low as 3 to 6 months), efficient and high fidelity emplaced node systems in deep-water, and the introduction of permanent systems for monitoring onshore. We can guess that future developments will include broader bandwidth, wider azimuth, and the installation of more ocean bottom node permanent reservoir monitoring systems benefiting from fibre-optic technology leading to great improvements in sensors and communication links.
As acquisition technology has advanced, processing technologies have not stood still, bringing NRMS values to impressive levels of sub 20%.
Future field challenges will be harder to deal with
So what will be the drivers of tomorrow’s technologies, what will be the backdrop within which our technologies compete and flourish? Over time, field challenges will become much harder as we diversify the application of 4D, making extra demands on our geophysics: deeper fields, strong geomechanical effects, fields with complex geometries such as sub-salt environments, hard rock or fractured carbonates and gas fields. As some fields near the end of their natural lives, we also have the intriguing challenge of using 4D effectively to monitor production decline and evaluate the timing of cessation of production to ensure safe and cost-effective field management. To rise to these challenges, as a community we must take on board knowledge and skills at a faster rate than ever before. We must respect the current buzz word in the industry ‘more for less’ – this will most certainly be here to stay, regardless of the oil price.
DIGITAL 4D will help in the future
In the next decade, the technical backdrop of other industries will become very important. For example, in terms of computer power and storage, we may be guided predominantly by Moore’s law. Some say that it will continue to be applicable as other physical devices such as quantum or optical computing take over – for the latter, however, their maturation trajectory is somewhat unknown. What is clear is that over the coming decades there will be a massive explosion in connectivity, communication and the amount of data we can process. This could well impact positively on our own industry – given a favourable economic environment for the transfer to flourish. There is a multitude of items that can be considered as incremental improvements for the future over the coming years. These include developments in sensor technology, some of which have been recently cited in the July 2016 edition of TLE, and also the amazing changes in source and acquisition technologies in general. Leading the way is fibre-optics and downhole DAS followed by automated lightweight downhole sources. Although sparse acquisition is an acceptable paradigm to reduce survey repeat time and gain valuable reservoir insights, the future technologies should be able to support large-scale channel count. To add to the mix, there are now many other emerging non-seismic tools that will come to fruition in the near future. For example, sensors detecting tilt and inclination on the seabed provide accurate monitoring of subsurface strains.
Figure. Future DIGITAL 4D system. More sensors, more data, more accuracy and more automation.
DIGITAL 4D means more accuracy
However, our advances still have a long way to go – an extreme example of this is the instruments recently used to detect gravitational waves with displacements the size of an atom. This was based on high-quality time-shift measurements between laser light propagating across two orthogonal cross-arms experiencing different strains due to the arrival of these waves. This is very sensitive indeed, but an example of what may become possible in the future. Strain/surface motion sensors can help constrain the geomechanical model and can be readily combined with 4D seismic data. Gravity surveys have been used with some degree of success, however, EM approaches have yet to develop to their full potential.
Figure. Can we detect gravitational-grade 4D Geomechanics?
DIGITAL 4D means more deployed physics
So one prediction we can safely make is that the field of the future will be well instrumented, the channel count will be high, and the data volume will be enormous. Engineers will have faster and finer simulations to interface with frequent automatic acquisitions. However as human beings will remain roughly the same, we will be unable to cope with this unless the smart/intelligent software is developed to handle the integration – to make sense of the information so that asset teams can utilise it effectively. We will need tools to handle the inevitable increase in data from a range of sensors, to automatically visualise the integrated dataset, and then to make clear and effective decisions. This will ultimately impact on training needs. The demand for new solutions grows exponentially and is highly marketable. I would anticipate existing physics will be more completely integrated into our algorithms and we will rely less on approximations we currently have built into our software – our current < 80% solutions still have plenty of room for improvement.
DIGITAL 4D means more automation and lower costs
So finally, how will the technology playing field of the next decade look like? I believe optimistically on the one hand that we can continue to improve our acquisition technology incrementally given a favourable economic climate. In the marine environment, we will need the power of areal coverage from multiple towed streamers but blended with the more focused quantitative interrogative power of node solutions (mixed with other sensor information from the seabed or downhole). Acquisitions will be very frequent, and the integrated datasets interpreted semi-automatically by advanced co-visualisation software. Migrations will work harder and smarter to provide high fidelity quantitative, amplitude preserving images. These, in turn, will help us to deliver 4D seismic in a cost-effective way to a broad range of currently inaccessible fields, as a tool for whole-lifetime monitoring from development, production to eventual abandonment.
About the author
Professor Colin MacBeth is an experienced 4D expert leading one of the 4D technology cradles – Edinburgh Time-Lapse Project. He has been involved in 4D technology innovation for approximately 20 years.
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