Presentation is loading. Please wait.

Presentation is loading. Please wait.

Seismic is not too complex for geologists - If you can understand convolution, you have it made. Simply stated, when downward traveling waves pass by a.

Similar presentations


Presentation on theme: "Seismic is not too complex for geologists - If you can understand convolution, you have it made. Simply stated, when downward traveling waves pass by a."— Presentation transcript:

1 Seismic is not too complex for geologists - If you can understand convolution, you have it made. Simply stated, when downward traveling waves pass by a set of reflecting interfaces, the reflected energy at any point is the sum of the products of each of the interfaces times the corresponding wave amplitude. Deconvolution is the reverse - i.e. the process of solving for these interface values using an estimate of the shape of that wavelet. Inversion is just another word for that process. I think most professional geologists can handle that. Since there is a heavy tie between reflection coefficients and well logging, understanding the importance of inversion should come naturally. Of course there are arguments about how to approximate the wave shape, and what to do with the computed coefficients. Those I am involved in are on whether to compute using statistical optimization (in the time domain), or whether to move into the artificial frequency and phase domains (which depend on statistical modeling). But that does not affect the understanding of what deconvolution and inversion are, and those arguments do not have to involve higher mathematics, so I urge all to pay attention. The results of processing decisions made from these calculations affect the whole industry, from exploration to reservoir modeling. The problem with leaving the processing decisions to the mathematical theorists is that they have gone too far with their attribute calculations, seemingly losing sight of reflection facts that do not require advanced math to understand. The first of these facts is that the seismic energy continuum consists of thousands of independent primary reflections, each coming from a single reflecting interface. These individual primary reflections do not mix in the subsurface. Earth filtering creates trailing lobes, the dominant frequency of those lobes decreasing with time. Because of the.huge difference in to and fro travel time between traces, this filtering creates big differences in primary reflection wave shape. The second (but associated) fact is that this travel difference shifts the relationship between primaries. To illustrate the importance of this, suppose the second lobe of the top primary is lined up with the first lobe of the bottom. The fact that the two primaries have opposite polarity means that a lime might look like a gas sand. Of course all variations in between will occur. I ask you to stop and consider that these two items are reflection facts, not opinion, and that they must be considered in any effort to improve resolution. Together they probably explain why some success has been obtained using angle stacks, and also that together they tend to make AVO claims questionable. On the next slide you will see the menu for my collection of non-linear seismic thoughts. There I go on to discuss more topics I consider important.

2 Introduction – take a minute to see where I am coming from and why this might be worth your time. Then look at some great well log matches to see the merits of non-linear optimization. Or some seismic basics all interpreters should be aware of. And now look at some sources of seismic noise And a quick look at refractions spawned by critical angle crossing. Now to the results of noise removal on a deep South Louisiana project. Or back up to look at the system in action on this last one. Sit back and watch the timed slides. Or here to the results from seemingly hopeless Permian basin data. Or here to still another example of down wave truncation. Or here to where I first identified strike slip faulting on a North Sea project. Or here to a Gulf Coast strike slip fault example. Or here where I discuss direct reservoir detection. Or here for a different discussion of intertwined signal and noise. Or here for a different twist on why ignored noise saved prospects for newcomers. Or here for a more complete noise primer. Or here for a comprehensive look at my inversion. Or here for another look at well log matches. Or here for a fairly sarcastic look at near/middle/far stack options and a wrap-up. This is the router in Paige ’ s set of non-linear seismic thoughts. If you were there, browsing through would be super fast and simple. To get there, see next slide.

3 I have spent a good bit of time collecting PowerPoints into a folder, which I have sent to my FTP site. If you are interested, You have to do the following to access the work. 1. Enter " adaps.exavault.com " in your browser and go there. The username is adaps and the password is adaps1.. 2. Select the folder PN and "download all". It sends a zipped file. Create a new folder on your PC named PN, unzip and load the two files (shows and base.ppsx) into PN. 3 access "base.ppsx" and you will get the router which will lead you to all the others. This eliminates the load time problem. Thanks in advance Dave Paige


Download ppt "Seismic is not too complex for geologists - If you can understand convolution, you have it made. Simply stated, when downward traveling waves pass by a."

Similar presentations


Ads by Google