Presentation is loading. Please wait.

Presentation is loading. Please wait.

1.The seismic energy continuum consists of thousands of independent primary reflections, each coming from a single reflecting interface. 2. There is no.

Similar presentations


Presentation on theme: "1.The seismic energy continuum consists of thousands of independent primary reflections, each coming from a single reflecting interface. 2. There is no."— Presentation transcript:

1 1.The seismic energy continuum consists of thousands of independent primary reflections, each coming from a single reflecting interface. 2. There is no mixing of primaries in the subsurface. 3. Geophones can only record the energy that exists at instants of time, and this forces an accidental form of compositing at the recording point. 4. The earth filter generates trailing lobes with travel, gradually emphasizing lower frequencies. The total travel difference from inner to outer station is great and by the time the energy reaches the recording points there will be significant differences in primary wave shapes. This (mostly ignored) problem is exacerbated by excessively long spreads. It heavily affects gather trace character, probably dwarfing any possible AVO effect. 5. The separation between primaries changes with offset, modifying the way they combine at the recording point, again affecting gather trace character. As with the earth filter, it happens before any processing can be done. In summary, the stack will produce an almost accidental waveform mixture. Basic reflection theory that mathematicians should keep in mind. INVERSION ATTEMPS must honor these points. They provide good arguments for non-linear logic that gets the best answer under the circumstances. So follow the doit yourself icon for other postings

2

3 Continuing with a discussion on deconvolution - A seismic trace is the product of a down wave vector convolved with the vector of all interfaces. Deconvolution theoretically is the process of solving for those interfaces by removing the effect of the wavelet shape. Frequency domain approaches attempt absolute solutions, where time domain approaches just shoot for the best answer possible under the existing noise conditions. Frequency domain approaches transform the observed frequency spectrum to an ideal target. My time domain approach attempts to statistically explain the input trace via the combination of a set of waveform guesses and a set of interface guesses. It utilizes a massive, layered approach, starting with initial guesses and proceeding on subsequent passes by computing a new set of wavelet guesses from the previous answers, minimizing the remaining trace energy. Reflections represent contiguous breaks in velocity. Deconvolution theoretically isolates these breaks, but because the resulting matrix of guesses is so tightly layered, lithologic interpretation is still difficult. From a geologists point of view, the image display of a sonic log is preferable. A sonic log is obtained by integrating well based velocity measurements. The ADAPS software simulates this by integrating its velocity interface guesses. Remarkable well log matches prove the system knows what it is doing. Two before and after integration are shown below. Integration can flip polarities. The fact that people have difficulty with this shows they suffer from a common misconception (that they see beds on seismic sections rather than individual interfaces). Because it is so important, I spend the next slide on this polarity phenomenon.

4 Please toggle w after Before The toggle test – You can call it professional carping, but over the years of competing for attention with the developers of frequency domain inversions I have noticed a blatant disregard for polarity. This is true in their attempts to show their synthetic trace in comparison to the input data. Some, looking at the well match on the Before side of this test might say that well match correlation is not bad. But: place one finger on the right arrow and press the left arrow to start Then keep toggling until you get the picture. Note the complete reversal of polarity in the very center, then pay attention to the nearly perfect polarity matches after integration (red is for low velocity and blue for high). This is strong logical proof. While toggling, remember that before integration, the individual nodes represented single interfaces, while after integration they approximate bed lithology (as represented by the sonic log that is shown in the middle of both). Individual node polarities will at least shift. Just remember it’s the amplitude/polarity pair we’re matching. Then, hopefully after you are convinced, go back to the fourth paragraph on slide 2, that talks about the interface events being spread apart by differences in effective offset velocity. As I have said, this spreading eliminates the need for the basic AVO justification.

5 Please toggle w before After The toggle test – You can call it professional carping, but over the years of competing for attention with the developers of frequency domain inversions I have noticed a blatant disregard for polarity. This is true in their attempts to show their synthetic trace in comparison to the input data. Some, looking at the well match on the Before side of this test might say that well match correlation is not bad. But: place one finger on the right arrow and press the left arrow to start Then keep toggling until you get the picture. Note the complete reversal of polarity in the very center, then pay attention to the nearly perfect polarity matches after integration (red is for low velocity and blue for high). This is strong logical proof. While toggling, remember that before integration, the individual nodes represented single interfaces, while after integration they approximate bed lithology (as represented by the sonic log that is shown in the middle of both). Individual node polarities will at least shift. Just remember it’s the amplitude/polarity pair we’re matching. Then, hopefully after you are convinced, go back to the fourth paragraph on slide 2, that talks about the interface events being spread apart by differences in effective offset velocity. As I have said, this spreading eliminates the need for the basic AVO justification.

6 Allow them time to load! A PowerPoint compendium of seismic topics Basic reflection theory the experts seemed to have missed. Inversion and integration – the all important sonic log simulation. Coherent noise background – an explanation of types. Removal of coherent noise on Gulf Coast – a breakthrough. Vibroseis de-noising – another (but similar) breakthrough. Strike slip faulting – salt dome association – new thinking. North Sea strike slip interpretation – the importance of resolution. About Paige - MS in geology,spent 7 years in Venezuela for Mobil,& then Phillips Maracaibo interpretation found Phillips’ major field there. Back to states, joined Phillips computing, became project manager for exploration. Hired by Western Geo. To start digital operations in Shreveport. Wrote first predictive deconvolution program that put Western on the map in digital processing (and formed the non-linear basis for later ADAPS software), After brief sojourn in commercial processing (where he wrote a table driven programming system), joined Dresser Olympic as both manager of processing and of research. Went on his own to start non=linear development. Consulting package consists of Paige’s personal time, his open-ended software and use of his processing hardware. Unless full segy detail is requested (segy output), the product is a series of PowerPoint studies. He can be reached at


Download ppt "1.The seismic energy continuum consists of thousands of independent primary reflections, each coming from a single reflecting interface. 2. There is no."

Similar presentations


Ads by Google