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Sandy, England, UK
There is no shortage of earlier articles like this in GEOPHYSICS, TLE, and the journals of other relevant societies and, of course, they tend to appear at major milestones such as 25-year anniversaries and their multiples, century changes, etc. Some have made accurate predictions and some have been way off the mark—and I've enjoyed reading all of them. Take for example some of the opening words from Paul Lyons' presidential address exactly 50 years ago:
This year marks the 25th anniversary of the Society of Exploration Geophysicists and the 25th year, approximately, of geophysics as an important industry.... There are now 4450 members of the society, an all-time high. In spite of this, these are trying times for many geophysicists. This has been brought about by a decline in the use of geophysical parties, especially in the United States.
It sounds familiar, and we could chuckle about it and try to recall how many times these words have been applicable since 1955, but look also at his closing remarks:
In conclusion, it can be said that in the future there will be available advanced instruments, new techniques of exploration and interpretation, electronic machines for computation, and new ideas to be applied to geophysics. The most important of these are ideas.
We could be critical and say it's a bit unspecific, but remember this was written about 10 years before the digital revolution, so he was certainly correct and possibly even daring in his predictions.
To see what happens when we try to be specific and objective in our technology forecasting, we could briefly review the Delphi exercise, which was conducted by SEG in 1982. In an iterative procedure, correspondents over a broad spectrum of the industry were asked to identify important technologies, the likelihood of eventual successful implementation, and to give their predictions for its year of implementation. The results were condensed down to 56 technologies, and to pick just four examples:
The first of these was achieved. The second two illustrate a common problem in the survey, which was to grossly underestimate the time which it would take the industry to develop and implement important technologies. The last one was probably unrealistic. I reviewed the list again recently and taking the 40 or so technologies which had been given a 75% or greater likelihood of being implemented, I considered that around half had still failed to materialize even in 2005. For all these, Delphi had predicted dates prior to 2000, typically 1995.
But enough of the past, except to point out somewhat sardonically the bad news that technology advances in our industry generally take much longer than we predict, and the good news that the unfinished Delphi list indicates that there is certainly still some work to be done!
Moving now into the forthcoming quarter century, and hopefully having learned some lessons from the previous one, I shall predict developments both in "conventional" 3D seismic (as in exploration/appraisal/development), and in reservoir surveillance.
Conventional 3D seismic will undergo both incremental improvements and a quantum leap. Because it sounds a bit bland and unexciting to say there will be incremental improvements, I will specify what these will be, and we should remember that although we may not always notice the increments, they become quite significant over periods of typically five years, and thus seismic surveys continue (and will continue) to be reshot and reprocessed to advantage. The reprocessing cycle tends to be faster than the acquisition one, probably because algorithmic ideas remain prolific and are faster to implement than new field equipment (especially in a conservative industry, and it costs a lot more to implement field changes).
These incremental improvements will be made mainly in our understanding of what we currently call noise, which unfortunately masks reservoir signal on most of our field recordings and on some of our processed data. I'm talking about "geologic" noise, not ambient noise, with several justifications. Firstly, on a well-designed survey, the amplitudes don't usually decay to the ambient level until well after the end of the "record." Secondly, whenever we repeat a record with the same shot and receiver geometry, the "noise" replicates very accurately. Thirdly, using some simple modeling and calculation, we can often predict that our reservoir signal should be above the level of ambient noise, at least over some predictable bandwidth. As an example, we might calculate a total reflection signal attenuation of 90 dB at 10 Hz, 114 dB at 50 Hz, 144 dB at 100 Hz, and 204 dB at 200 Hz. On a marine survey with an air-gun output of say 80 bars (referenced to 1 m) and an ambient noise (streamer tow noise) around 8 microbars peak-to-peak, this ambient noise should allow reflection signal detection even after an attenuation of 10 million to 1 or 140 dB, and maybe more due to the data redundancy, so let's say 156 dB or thereabouts. So in examples like this one we should see our reservoir over quite a wide bandwidth, but usually we do not. (I should of course show the modeled wavelets and air-gun signature spectra, etc., since there are strong frequency dependencies, but these simple calculations will suffice.)
This "geologic" noise comprises statics, trapped energy, multiples, refractions, scatter, anisotropy, and interface issues such as mode conversions.
We will continue to learn how best to sample the geologic noise and thus how to attenuate it or, better, invert it, because one person's noise is often someone else's signal. This learning will be driven by those who work at the leading edge of the data-processing activity, but they will only be enabled by close cooperation with the acquisition, equipment, and funding communities.
I am encouraged to make the above prediction because I see developments which are clearly heading in this direction. One such development is the recent opportunity to record surveys using single sensors instead of arrays of detectors, and this is especially encouraging because some of these early case histories have been on land data on which the geologic noise is generally much worse. See for example the field data comparison in Figure 1 and the relevant processed sections in Figure 2 (Anderson et al., 2005).
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Again on land, three-component technology has seen occasional use over the last quarter century, mostly in "research" mode and mostly unsuccessfully at least in a commercial sense. However, the technology now exists to retest this technique with much improved sampling, and it seems intuitive that if the sensors on a "single sensor" survey were three-component sensors, then there would be many cases (not all!) where the noise would respond to (for example) polarization filtering, thus providing an additional quality increment. This seems especially obvious on 3D surveys where the shooting geometries result in much trapped energy impinging on existing geophone arrays at oblique angles or even at right angles. I hesitate to predict that shear-wave signal data will be used on land in the next 25 years, as I suspect that near-surface complexity will defeat it, but it would be nice to be wrong on this one, and techniques such as drilling shallow horizontal instrumented boreholes beneath the complexity (Bakulin and Calvert, 2004), might enable it.
Just occasionally in our industry we do have "quantum leaps" in technology, and in previous quarter-centuries these have been redundancy of coverage, the digital revolution, and the move from 2D to 3D surveys. I predict one for the next quarter century, and it will take place with ocean-bottom recording and processing. OB data have the potential to be both well-sampled and symmetrically sampled, and to allow us to record all source-receiver offsets and all azimuths for each common reflection (or conversion) point, and to utilize both particle motion and pressure data. The seismic volumes acquired in this way will teach us much about noise sampling, identification, and its removal or its eventual inversion. The bandwidth will be wider both at the low and the high end of the spectrum. These seismic data cubes will take the seismic process up to a new level of performance at a price we can afford. It will be exciting to work with them in the areas of processing algorithm research and visualization technology, two areas which have served us so well in the last 25 years (or in any subset we can think of). Additionally, these data volumes will allow us eventually to quantify the earth's velocity anisotropy and to use shear-wave energy for more than just "gas chimney" problems, despite the fact that the processing and interpretation difficulties are at least an order of magnitude greater than for P-wave data. Also, we will integrate the surface seismic with the data which increasingly are becoming available from downhole engineering. We can expect routinely to have pressure, temperature, and saturation data from the region of the well completion, and possibly also inwell and crosswell seismic data.
These azimuthally well-sampled surveys are also the probable answer to the illumination problems or image shadow zones which occur in areas of severely complex tectonics such as the salt bodies of the Gulf of Mexico.
Once satisfactory subsurface image cubes have been obtained for interpretation (and they will be several, for example the lithological cube and the fluids cube), the requirements change, because the next step is reservoir surveillance. Here we will see continued improvements in the repeatability of time-lapse recording and thus incremental improvements in the sensitivity of the "4D" method. So far, it does seem that the best repeatability is achieved with emplaced receiver systems, so we will see these become commonplace.
It has been wonderful to observe the early pictures from the world's first major emplaced seismic system at Valhall showing the saturation changes in the reservoir over just a few months (Figure 3), from Barkved et al., 2005. The reservoir engineers can anticipate movies of the fluid and pressure changes over time in their reservoirs.
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Lots of untapped possibilities exist for time-lapse surveys. As discussed above most of the "noise" in our seismic data is generated by the seismic source and is geological in origin. Given the same source and the same near-surface conditions, most of this "noise" should cancel during the subtractive nature of 4D data processing. Equally, it seems intuitive that to see changes in the reservoir, we will not need the finer sampling required for a high-resolution 3D cube. Thus, these emplaced receiver systems once proven, can be much sparser, and thus more commercially attractive for smaller reservoirs.
Possibly the ultimate in repeatability can be obtained using both emplaced sources and emplaced detectors. It was a revelation for me to see repeatability measured in microseconds demonstrated by CGG and Gaz de France (Meunier et al., 2001) in which even the diurnal temperature variations in the near-surface could be observed. Further, such systems can use very low-power sources (running continuously to build up the energy). These will be environmentally acceptable.
Regarding data management—based on past performance—the technology which is used to store and manage data will fail to keep up with the gargantuan requirements of seismic acquisition and processing.
There will be socioeconomic imperatives during the next 25 years. It seems very likely that the continuously increasing demand for oil will outstrip the planet's supply capability at some time during this period. This is likely to increase the oil price considerably and will be highly disruptive in many ways. There will be incentives to explore in areas where exploration and/or extraction are currently uneconomic, and it will highlight the fact that the average recovery factor from oil reservoirs sits at around 40%. Time-lapse seismic, and any other technique which can impact this low figure, will be hugely popular.
Finally, what will our society look like at the end of 25 years? The shift in emphasis from exploration geophysics to reservoir geophysics (which has been incremental but continuous for at least 20 years) will continue. There will be an increase in interest in mining geophysics, as shortages of several raw materials will become acute. Water supplies will also be seriously problematic in several regions of the world, so there will be an increased focus on hydrogeology which will involve near-surface geophysics. It would be surprising if the mergers and consolidations which have affected the oil and gas industry are not visited upon the professional societies to some extent. However, communities of specialists always need a forum for exchange of ideas and best practice and for exhibitions of commercial products, so the society which exists in 2030 needs to provide that in an efficient manner, and it must do so equitably in a global context (Figure 4).
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