Challenges in Oil and Gas discoveryHeadwave’s Visualization technology has a big impact on the challenges in Oil and Gas Industry. It improves the quality and speed of business decisions. It brings the seismic prestack domain to the interpreters and allows the processors full visualization of pre- and poststack. The Headwave tools work both on a regional scale as well as on reservoir studies. They provide the security to know that the data has been thoroughly vetted and that decisions made on this data are well founded. It drives increased ROI and ROE.
IntroductionChallenges in Oil and Gas discovery are not new. The pressures and temperatures experienced by drillers and producers have caused many headaches. With the increasing difficulty to find new reserves, the Oil & Gas Industry is facing the equivalent pressures in finding seismic tools which work at depth. Now Seismic Imaging is struggling with locating and viewing potential resource plays at seven to ten mile depths in the earth, while generating those images from seismic sources which are up to two miles from the sea floor. All of this combines to make the signals sought fainter than ever before. This, in turn, requires massive increases in processing power. Where will it be acquired? What kind of a budget is that going to take? This is all addressed by Headwave in an innovative fashion.
Deep Views with Prestack SoftwareHeadwave has developed the first highly accelerated, prestack visualization and computation software package. While prestack has been long used for AvO and RMO analysis, the interpretation process has been used has been arduous. With multi-fold gathers, interpreters have struggled to get a clear overview of what was going on. Thirty fold gathers were barely manageable on a 24” display, but 50-200 fold gathers were really out of the question. Headwave has changed that with the ability to volumetrically view the prestack data. No matter how large the prestack dataset – we’re talking > 1 terabyte datasets – the user can access it from the desktop. Headwave’s user-selectable compression delivers multi-terabyte datasets to the desktop and makes using the data feasible. Interactively work with a terabyte dataset on a standard PC workstation. See vast swaths of data in a manner never before presented.
Figure 1. Two views of the same inline and associated prestack data. On the left a gather is displayed and a prestack probe is also shown for the inline data. On the right, the probe has had the shader modified to make all but the trough peaks transparent (blue = trough) in the probe. The nature of the far offset booming is clear, and from the gather data, a revisiting of the muting of the prestack data might be in order.
Volumetric Visualization Volumetric visualization means the data is seen as a volume in space. Moreover, the data is seen in context. Each gather is associated with the poststack trace generated from the gather. This makes it easy to relate individual prestack traces to the poststack, additionally gather flatness (NMO quality), muting quality, and RMO quality are easily seen. It’s possible to scroll though ten MCS blocks in a single afternoon on an inline–by-inline basis viewing each gather. Users no longer need to avoid looking at a 1000 sq Km region in prestack. The ability to load such a dataset on a single workstation and do QC is unprecedented. This means that full processing QC is possible in a single day. To do so, the poststack data is loaded into the workspace and linked to the associated prestack data. Now the prestack data may be displayed in many ways: one gather at a time, offset slices or as a prestack probe. Even a HyperCursor can be used to see the prestack info at a special location. In this way, the viewer can walk through the prestack volume and inspect all traces at a given offset, or each gather in a given volume. Having assured oneself and the group that the data processing results are as expected, now the power of volumetric visualization can be fully utilized. The user can easily adjust the transparency of the prestack data volume. In doing so, AvO indications can be seen. By inserting a probe into the volume, the specific regions of interest can be viewed in more detail. Closer inspection can lead to selections of gathers for custom stacking. Near, middle, and far stacking can be done on the fly. Stacking can also be done on a trace range basis.
Prestack Horizon PickingPicking a horizon in poststack data is commonplace, it’s not so common to pick a horizon in prestack data, and even less common to use a poststack horizon to seed the prestack pick. The picked prestack horizon can be used to map various attributes. Attributes such as horizon curvature, time delta (the difference from the time of the event at offset 0 to the time of the event at offset n), trace count (how many traces of the gather contributed to the poststack trace), Gaussian curvature, or others can be derived or loaded and mapped onto the prestack horizon. The user can step through the entire poststack volume viewing the prestack horizons associated with that inline. At any point the attribute being displayed may be changed and the stepping continued. This is an example of how the tools available in Headwave can be applied. Contrast this to the previous methods of viewing prestack gathers on a large dataset and it’s obvious that this is a huge leap forward for ease of use. Prior methods required either a system with memory larger than the prestack dataset, or required a laborious loading of 2D panes of gathers, up to 10 on the screen if you were lucky. The major problem: the more prestack on screen, the less the poststack overview, and forget trying to load a 100 fold gather, let alone all such gathers related to an inline or crossline. This is not a problem for Headwave. Wide Azimuth Surveys aren’t a problem, nor are the new circular surveys with 200 fold coverage.
Figure 2. Here are four 36 fold gathers and a prestack probe displayed together with the poststack inline, two time horizons are displayed as well. This display is next to impossible in a 2D display mode.
Imperfect Prestack Data and AvO Suppose that the prestack data that is available isn’t perfect. How can we apply AvO? With the computational power now available through Headwave, corrections can be applied, interactively, on the desktop. Maybe additional filtering would help, or maybe it needs a minor velocity tweak and a test of the stacking parameters to optimize the poststack trace or improve AvO calculations. This is all possible. Stacking can be done either on the full volume, or on a selected probe. Since the probe is a subset of the entire data volume, stacking can be performed quickly. Sometimes the prestack data won’t have a mute applied or the applied mute needs adjustment. In Headwave the mute parameters can be tested. They can be designed on the prestack data gathers and the stacked result directly inspected. As previously discussed, partial stacks are also possible, and quickly accomplished.
After all the interactive QC, and with carefully applied local corrections, Headwave offers extraction of the AvO parameters on the prestack horizons for crucial studies of reservoirs and leads.
Figure 3. Here is an example of checking for an type II AVO effect. The prestack volume has had a custom shader created which highlights both the low level peak (red), and the phase change to an increasing trough (blue). A poststack horizon has been picked and used to seed a prestack horizon. The prestack horizon shows that the peak transitions part way through the gather, thus further evaluation should be undertaken. At the same time the prestack data shows that velocity picks may have been suboptimal.
What’s good for 3D is even better for 4D. Full use of prestack 4D data lets users easily see changes, changes in a horizon for sure, but even more, changes in volumes. Volumetric visualization gives “visual pop” to reservoir changes: evaluates reservoir response with time lapse seismic. Multiple datasets can easily be merged for comparisons, delta calculations, and more.
When serious money is spent to follow changes in the reservoir, then a serious visualization package should give full money’s worth. If all there is to demonstrate a major change in the reservoir is a single thin horizon, then the real details have been lost. Is there any other data, or is there another change that’s there? With Headwave you can see, in detail, the full 4D results also with all its prestack variation. Blending of datasets is easy, and with transparency adjustments, changes in the reservoir are clear. The reservoir boundaries are clear, and more importantly, the volume is there. If completion is through multiple layers, then each of those layers should be clearly visible. Make sure that the stacking that’s done optimizes the signal to noise ratio, play what if, with stacking and filtering. Drive information examination until the current state is clear and presentable. To that extent Headwave has also developed a Prestack Plugin for Petrel.
Saving the Planet and the BudgetHeadwave has chosen to use the power of the floating point units in graphics processors to accelerate computations. Headwave is a leader in this technology. Both NVIDIA and AMD/ATI now offer graphics chip derived computational engines. They are fast and it appears that not only is computational power useable, but the seamless availability of visualization with computation provides substantially shortened time to discovery.The good news is that by going to this technology, the cost, whether $ per Gigaflop, or Watts per Gigaflop, has gone down, way down, down by a factor of 10 – 30 for real world applications in Headwave.
ConclusionsHeadwave has developed novel technology for the Oil & Gas Industry based on GPU processing. With the advent of GPU processing on a single graphics card or even in clusters, its interactive prestack visualization and computational tools are available today for large, very large, and extremely large datasets. While the Headwave tools can handle regional datasets, they are also perfectly suited for smaller, field-wide surveys. In both cases, Headwave tools shorten the time to target.Headwave’s tools provide the security to know that all data has been thoroughly vetted and that decisions made on this data are well founded. It drives increased ROI and ROE.
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