- #Seismic well tie tutorial hampson russell software#
- #Seismic well tie tutorial hampson russell free#
In an air gun array you can shorten the signature in time by smoothing out spikes in the frequency spectrum caused by oscillating air bubbles, and then converting it to minimum phase.
The purpose of signature deconvolution is to find a filter which shapes the measured source signature into something with more resolution, without changing the noise too much. For a marine source, we can determine the wavefield of a source array by measuring its response with a sufficient number of near-field hydrophones. There's a Dallas company, however, which makes a device which bolts onto the base plate and measures the ground force directly. With Vibroseis, our current measurement does not account for base plate bending. The signatures are related by a scaling function, allowing you to derive them. How do we measure the source signature? For dynamite I propose we fire two shots of different sizes. Thus measuring the source is just as important for structural interpretation as for stratigraphic. Removing them is difficult because you don't have stacking to help you, but it can be done if you know the source depth, receiver depth, and source signature.
#Seismic well tie tutorial hampson russell free#
The most important multiples are those introduced by the free surface. This assumes all energy is primary, so you must remove multiples first. If post-stack migration doesn't work because the structure is too complicated then you have to do pre-stack migration. It's better to include the measured source signatures and the geometry of the sources and receivers, and process this to stack as you did the data. This model cannot account for shear waves. With well-ties our synthetic seismograms are normally computed using plane waves at normal incidence to the earth. Even then you must not damage the signal-to-noise ratio, so you can't change the amplitude spectrum too much. Deconvolution can only be used to get rid of convolutional effects such as the source time function and the receiver response. You can't remove it through deconvolution because it isn't convolutional - the arrivals have taken many different ray paths and so have been attenuated differently. I believe that the phase problems you have in Alberta demand a radical change in approach which must start in the data acquisition.Ībsorption must be included in the wave equation to compensate for it correctly. I argue that this so-called wavelet doesn't exist. I've been told that the measurement of the signature is irrelevant because the wavelet that comes back from the target looks nothing like what goes in at the surface. Why Do We Need to Measure the Seismic Signature?īy measuring the seismic signature, you provide severe constraints on the models you can use to fit the data. I suspect that our ability to get the wavelet phase right hasn't progressed continuously, and I would like to know why.įinally, what are the current methods people use? What is the state of the art? Anton Ziolkowski (University of Edinburgh): It must be that in 1993 we're much better at getting a zero-phase section than we were in 1976, but I'm not convinced that's true. Through the course of time we worried about instrument dephasing, and then homomorphic, maximum-entropy, maximum-likelihood, and multi-component deconvolution. Second, why is it so hard to get it right? I've been in the business since the middle 70's, and the first thing we heard about were the problems with spiking deconvolution. I've thought of three issues which I would like to see resolved during the course of this workshop: First, who cares about wavelet phase? Why is it important?
#Seismic well tie tutorial hampson russell software#
The workshop began with some remarks by the chairman: Dan Hampson (Hampson-Russell Software Services Ltd.): The discussions following each talk are included in more detail.Īlthough written in the first person, these notes have been edited for clarity and brevity, and should not be taken as direct quotes. These talks are summarized only briefly here since the abstracts can be found in the convention program manual. Six presentations were given, beginning with the keynote speaker Professor Anton Ziolkowski from the University of Edinburgh. The workshop was organized by Peter Cary of Pulsonic Geophysical Ltd. As these notes show, we are still far from a consensus. It produced a fascinating look at a subject which, despite its longevity, continues to present major challenges for exploration geophysics.
On the afternoon of May 6, 1993, the final day of the annual convention of the Canadian Society of Exploration Geophysicists, a workshop entitled "Problems with Phase" was held at the Calgary Convention Centre.