Author: Mike Cline, T/X Resources
Here are the results from another one of my Do-It-Yourself spreadsheet applications. This one creates a pseudo-shear log from a sonic log, using John Castagna’s “Mudrock Line” technique.
Often, shear sonic logs are difficult to acquire, so we may end up using a “default” shear log suggested by our AVO programs, which commonly use either a Poisson’s Ratio of 0.25, or a Vp/Vs ratio of about 2.0 to calculate the shear log.
However, there is a much better way, which Castagna illustrates in his classic 1985 paper (long title) “Relationships Between Compressional-Wave and Shear-Wave Velocities in Clastic Silicate Rocks”. In his article, he demonstrates that there is an excellent linear relationship between the compressional, and shear velocities of clastic silicate rocks, a technique which I have used many times, with successful end-results for many of my clients.
See the larger Adobe Reader pdf file.
Author: Mike Cline, T/X Resources
For those of you that haven’t had a chance to try out the Coblending feature in version 8.2 of SMT’s VuPak module yet, I would suggest that you give it a look. If you’ve never used anything like it before, be aware that it could max out your wowie-meter! Excuse the enthusiasm, but I like cool (and useful) technology.
(Back in the real world now) What is Coblending? It is just as its name implies—it is the ability to blend two different volumes of seismic data together, and display them both at the same time. Besides being very cool, it could also really be helpful with seismic interpretations—especially in complexly faulted areas.
See the larger Adobe Reader pdf file.
See the VuPak animation
Note: The avi file is fairly large, so it will take some time before the animation starts.
Author: Mike Cline, T/X Resources
Do you have a new 3D seismic volume that you need to review quickly? Maybe you just need to scan it to get a feel for the structural trends, or for quickly finding new prospects to concentrate on.
Whatever the case, SMT’s VuPak Chair Cut Animation, a common method of seismic visualization, is a good approach to use for the evaluation. It allows for the simultaneous viewing of three different planes of seismic data, as seen in the image below—Inlines (vertical data surface facing forward), Crosslines (vertical data surface facing towards the left) and Time Slices (horizontal data surface, facing upwards).
The data set being displayed below is a Coherency volume, which is an excellent seismic attribute for highlighting subtle structural and stratigraphic changes in the data. In this case, we’re looking for the major fault trends. Seconds after opening the volume for viewing, we find that there are two significant faults surfaces (the dark purple, linear features being highlighted by the red arrows), which can be seen traversing through various faces of the cube of seismic data volume.
See the VuPak animation (25MB Media Player avi file).
Note: The avi file is fairly large, so it will take some time before the animation starts.
Author: Mike Cline, T/X Resources
While we’re on the subject of channels…………….
Here is a “quick-look” visualization technique, accomplished within SMT’s VuPak program, which can be used for prospect scanning of new 3D seismic volumes—either standard migrations, or other seismic attributes such as angle/range-limited AVO (amplitude-versus-offset) volumes.
This prospect scanning technique highlights interesting seismic amplitude details in much less time than when standard, vertical seismic displays are used for the interpretation, and it also lessens the chance that subtle anomalies will be overlooked. The example shown here, is another presentation of the channel in the previous two postings, and is accomplished by quickly discriminating larger amplitude events from the “background noise.
See the VuPak animation (29MB Media Player avi file).
Note: The avi file is fairly large, so it will take some time before the animation starts.
Author: Mike Cline, T/X Resources
After I finished the earlier posting, “Shaded Relief Maps for Subtle Fault Detection“, it occured to me that there may also be an interest in map displays for stratigraphic interpretation. This posting, and the one that immediately follows, illustrates how various map types and parameters can affect a stratigraphic interpretation presentation.
In the first slide in the series below, an autopicked two-way time color-filled map, a channel-like feature can be seen in the upper left quadrant of the mapping area. As we will see in later illustrations, it is fortunate that this colorbar was used—the channel may not have been as evident with other colorbars, as it is in this display. However, other than the two bounding faults (areas with the black crosses, indicating the manually-interpreted faults), not a lot of other structural and/or stratigraphic detail is evident. You can tell that the channel is draped across a nose, located between the red, high area to the northwest, and a gray area southeast.
See the larger Adobe Reader pdf file.
Author: Mike Cline, T/X Resources
Now for the less effective channel map displays:
Initially, I had included this portion in the original posting, “Effective (and Less Effective) Channel Maps” (see above). However, after thinking about it a while, I decided that it was too long, so I broke it up into two postings.
See the larger Adobe Reader pdf file.
As I mentioned in part one, the Channel TWT Color-Filled Map in the first slide of this series of images, is not as definitive because of the poor choice of colorbars. The upthrown fault block colored in red, increases the time range of the colors so much that the middle fault block, where the channel is located, is almost entirely in the green colors. This is the cause for the loss of color contrast, leading to less definitive channel edges. A map’s “dynamic range” (the spread of the largest-to-smallest values) is a key consideration when deciding on a colorbar.
Author: Mike Cline, T/X Resources
How fortuitous! I received my version 8.2 update of SMT’s Kingdom software this afternoon, and just got it installed. One of the new features that has been added to this version of 2d/3dPAK, is the ability to display the Shaded Relief of a grid. So, I thought that this would be a good time to introduce the technique to those viewers not familiar with the general concept. However, since I haven’t had a chance to get completely familiar with this newest feature in the SMT software, the surface and map displays shown below were created in my normal work flow using Golden Software’s Surfer program. As time permits, I’ll try to review, and compare, SMT’s new feature.
What is a Shaded Relief display? It is a map view of an artificially illuminated 3D surface whereby shadows are cast by minor deflections in the surface (shadowed deflections are facing away from the illumination source). This type of map is an excellent way to highlight smaller faults which may not have been seen, or noticed, on the vertical seismic displays.
See the larger Adobe Reader pdf file.
Author: Mike Cline, T/X Resources
Did you know that you can improve the resolution of most seismic data with a data processing sequence known as Spectral Whitening (aka. Spectral Balancing)? What is Spectral Whitening? It’s nothing more than increasing the bandwidth, or frequency content, of a seismic data set. The increase of the higher frequencies (naturally filtered by the earth) allow the interpreter to resolve smaller features than would normally be observed.
See the larger Adobe Reader pdf file (four pages).
Author: Mike Cline, T/X Resources
Usually, color-filled maps are utilized for structure map presentations. Preference, or habit? If this applies to you, why not consider using a 3D shaded surface display, which transfers so much more information than a standard color-filled map, to display an interpreted horizon or gridded surface?
The animated display below compares an “overhead view” of a color-filled map, with a perspective view of a 3D shaded surface display. The black crosses on the color-filled map indicate where seismic faults were manually interpreted (at 500′ increments—or, every fifth inline and crossline in the 3D seismic survey).
See the larger Adobe Reader pdf file (two pages).
Author: Mike Cline, T/X Resources
From time to time, we all have had a need for programs to view/manipulate geoscience data. Over several years I have collected a few website links that may be useful.
Here are a few links to free segy viewers that I’m aware of. Some of these are just basic segy viewing programs, but some also have editting capabilities:
1) Kogeo– Seismic data viewing, import/export, editing, navigation tools, and 3D visualization.
2) GSEGYView– Seismic data viewing, and some processing.
3) SeiSee– Seismic data viewing, import/export, editing, and plotting.
4) SeisVu– Seismic data viewing, import/export, editing, and plotting.
Author: Mike Cline, T/X Resources
Has this ever happend to you? Just as you are getting ready to plot a horizon/grid as a finished, color-filled map for an upcoming meeting (a short fuse of course), then you notice anomalous data ”spikes” and/or “black holes”, that really detract from the appearance (and credibility) of the map? Don’t feel too badly though, they aren’t always that obvious on most of these types of “flat” map displays—often seeming to appear out of nowhere.
To correct the map, you have to go through the tedious process of trying to find the bad data, fixing it, and then trying to recreate the display just as you had it earlier (with all of the same title block and scale info that you had before, but forgot to keep)? Arrgghhh……. There has got to be a better way!
See the VuPak animation (17MB Media Player avi file).
Note: The avi file is fairly large, so it will take some time before the animation starts.
Author: Mike Cline, T/X Resources
In this SMT VuPak 3D perspective display, only the largest 30% of the seismic troughs (negative amplitudes) have been selected. In conjunction with this amplitude extraction, the “Base of Channel” horizon, fault interpretation, along with the nearby wellbores have been selected for viewing. This results in an impressive cloud of large amplitudes, which exhibits a distinct, and channel-like sinuous character (red event, highlighted by yellow arrow), in close proximity with other controlling geologic features.
See the VuPak animation (18MB Media Player avi file), or see a larger Adobe Reader pdf file.
Note: The avi file is fairly large, so it will take some time before the animation starts.
Author: Mike Cline, T/X Resources
Since the first posting, I’ve gotten nothing but encouraging comments. Here are a few:
“Good work Mike.” (Michael M.)
“This is very interesting!” (David W.)
“Excellent idea.” (Teri B.)
“I think it’s a great idea.” (Sara V.)
“Works!” (Yvon H.)
“Wow! You did it.” (Mark C.)
“Thanks a lot for your blog, brilliant idea.” (Julien F.)
From the sound of it, visitors may be starting to realize the potential usefulness of the blog (at least I hope so), and how the old SMT User email forum might mesh with it. I also just checked my website stats, and the number of “hits” is up by orders of magnitude–so I know it has gotten some interest from viewers.
Author: Mike Cline, T/X Resources
Have you ever wished that there was a good, and easy-to-use program to capture just a portion of a screen, or menu item, or video?
Well, now there is one, FOR FREE! TechSmith, the makers of SnagIt have just offered a fully licensed copy of version 7.2.5 of their program on their website. This version is a slightly older than their most recent release (version 8.2), but it works very well. Not only that, but shortly after you register for their free version, they will even offer you a reduced rate to upgrade to version 8.2 (50% savings from the regular price).
See the larger version (2MB Adobe Reader pdf file)
Author: Mike Cline, T/X Resources
Well, as they might say in West Texas, “We’re in bidness (business) now”. No offense Midland SMT users!
It recently occurred to me that there might be some visitors who have recently stumbled into the blog from my website, that may not be a member of the SMT Users Group, so I thought that I would get them up-to-speed on the blog so far. The following text is an editted version of some of the emails that I have sent within the Users Group email forum, in the last few days.