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Johannes DOUMA

Country: The Netherlands
Degree Program: MS, Geophysics
E-mail: jdouma@mines.edu

CV

Curriculum Vitae

 

Johannes is a graduate student in Geophysics at the Colorado School of Mines. His strong interest in wave phenomena research led him to join the Center for Wave Phenomena. Johannes' advisor is Prof. Roel Snieder. He completed a project to optimize time reversal focusing through deconvolution for acoustic waves with Prof. Snieder and Los Alamos National Laboratory researchers TJ Ulrich and Brian E. Anderson. Additionally, he recently worked together with visiting researcher Dr. Ernst Niederleithinger on applying his method to a concrete block with embedded receivers at the civil engineering lab in Mines. He then began working on improving the locating of microseismic events. This work has been completed for both the acoustic case as well as the elastic case.

During the summer of 2012 and 2013, he worked at Cimarex Energy in Tulsa, Oklahoma under Dr. Steven L. Roche, where he worked in the exploration technology team. During his internships, he developed a new seismic attribute, a workflow to predict reservoir rock quality and potential EUR using seismic data, developing better elastic inversion for unconventional plays in order to high grade areas. Additionally, he worked closely with the Oklahoma team to assess and high grade new acreage. During his time, he worked on the data for the Permian, Mid-continent, and Cana region.

One of his main focuses now is building better low frequency models to be used for inversions. He combined his work from the Cimarex internships with visiting researcher Ehsan Naeini to publish a paper on using image guided interpolation to build better low frequency models for inversions.

 

Research

 

Experimental study: Deconvolution

Time reversal techniques are used in ocean acoustics, medical imaging and non-destructive evaluation to backpropagate recorded signals to the source of origin. We demonstrate experimentally a technique which improves the temporal focus achieved at the source location compared to time reversal. The experiment consists of propagating a source function from a transducer within a concrete block to a single receiver on the surface, and then applying time reversal or deconvolution to focus the energy back at the source location. The proposed method is simple and proven to be robust. Additionally, it's costs are negligible due to deconvolution being a preprocessing step to the recorded data.

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Locating a microseismic event using deconvolution

Microseismic events generate compressive waves and shear waves which can be recorded at receivers. We present a theory that shows how elastic P and S waves separately back- propagate to the original source location. These refocused P and S wavefields are free of singularities. We also demonstrate a technique that enhances the ability to image the spatial focus for each wave type using elastic waves. The improved spatial focus obtained is achieved in a velocity model for which the interface boundaries are approximate but where the mean slowness is correct. Deconvolution designs a signal to be rebroadcasted from the receivers, using only the waves recorded at each receiver, such that the wavefield has an optimal temporal focus at the source location. We demonstrate theoretically and numer- ically that improved temporal focusing of elastic waves leads to improved spatial focusing for each wave type. This proposed technique only involves a simple preprocessing step to the recorded data and its cost is hence negligible compared to the total cost of microseismic imaging.

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Correct velocity model and smoothed velocity model
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Deconvolution and Time Reversal

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a) and b) - temporal focusing
c) and d) - spatial focus

 

 

 

 

 

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