R. Holzner

Interpretation of Hydrocarbon Microtremors as Nonlinear Oscillations Driven by Oceanic Background Waves

Summary Hydrocarbon Microtremor Analysis (HyMAS) identifies the presence of hydrocarbon containing geological structures by analyzing low frequency seismic background wave signals. A possible interpretation of this reproducibly observable phenomenon is the excitation of hydrocarbon related resonances. Synthetic spectra produced by basic linear and non-linear one-dimensional models of an oscillating liquid filled porous medium show characteristic features of measured HyMAS spectra when oceanic background waves around 0.1-0.2Hz are assumed to be the external driving force.

Hydrocarbon Microtremors Interpreted as Oscillations Driven by Oceanic Background Waves

Hydrocarbon Microtremor Analysis (HyMAS) is an innovative technology for identifying the presence of hydrocarbon containing geological structures by analyzing low frequency background wave signals. A possible interpretation of this reproducibly observable phenomenon is the excitation of hydrocarbon related resonances. Synthetic spectra produced by basic linear and non-linear one-dimensional models of an oscillating liquid filled porous medium show characteristic features of measured HyMAS spectra when oceanic background waves around 0.1-0.2Hz are assumed to be the external driving force.

Spatial separation of circularly polarized laser beams in sodium vapor

We observed experimentally that a superposition of two co-propagating left and right hand circularly polarized laser beams is spatially unstable during propagation through a vapor of sodium atoms containing argon buffer gas. A small spatial asymmetry between the two input beams leads to their separation into two pure circularly polarized output beams. However a single linearly polarized input beam was found to be spatially stable. Our theoretical results from Maxwell-Bloch propagation calculations using both modal expansion and direct partial differential equation solution methods are in good agreement with the experiments. The splitting mechanism can be explained in simple terms as consisting of an absorption and dispersion dominated initial part and a diffraction dominated final part.

Dynamics of laser beam switching in sodium vapor

The interaction of left- and right-hand circularly polarized narrow-band cw laser beams that copropagate through sodium vapor and are tuned to the homogeneously broadened D1 transition can lead to the mutual extinction of both beams. Such beam switching is caused by an intensity- and polarization-dependent refractive index due to optical pumping even at low intensities. The dynamics of beam switching is investigated experimentally and explained qualitatively by the conventional J = 1/2 to J = 1/2 transition model. The accurate quantitative description, however, is only achieved by an extended model comprising hyperfine ground states in spite of homogeneous line broadening by argon buffer gas, which is larger than the hyperfine splitting.

Optical-pumping-induced ring structures of polarized laser light propagating through sodium vapor

We describe a sensitive technique for observing small transverse modifications to intensity, phase, and polarization arising in nonlinear propagation of a laser beam through an atomic vapor. The technique, which in essence is an interferometric one, is based on the use of crossed polarizers that are nearly but not exactly pure circular. Illustrative results are presented for cw dye-laser radiation propagating through collisionally broadened atomic sodium that is near resonant to the D1 line. Well-defined ring patterns produced by nonlinear interactions are observed at both positive and negative laser detunings.

Scientific Strategy to Explain Observed spectral Anomalies over Hydrocarbon Reservoirs Generated by Microtremors

A033 Scientific Strategy to Explain Observed spectral Anomalies over Hydrocarbon Reservoirs Generated by Microtremors E.H. Saenger* (ETH Zurich / Spectraseis) S.M. Schmalholz (ETH Zurich) Y. Y. Podladchikov (PGP Oslo) R. Holzner (Spectraseis) M. Lambert (ETH Zurich) B. Steiner (ETH Zurich) B. Quintal (ETH Zurich) & M. Frehner (ETH Zurich) SUMMARY Worldwide one has observed narrow-band low-frequency (1.5-4 Hz) tremor signals on the surface over hydrocarbon reservoirs (oil gas and water multiphase fluid systems in porous media). These ‘hydrocarbon tremors’ possess remarkably similar spectral and signal structure characteristics pointing to a common source mechanism even though the depth (some hundreds to

Using nuclear spins, radio waves, sodium atoms, and laser light to investigate spatiotemporal nonlinear systems

Within the wide field of nonlinear dynamics we investigate temporal and spatial behavior of electromagnetic systems. A strange type of laser, the nuclear magnetic resonance (NMR) laser, shows truly chaotic behavior and is therefore ideally suited to analyze experimentally and theoretically a variety of temporal nonlinear effects. Of particular interest is the analysis of its strange attractors in terms of unstable periodic orbits. For the extension of our research from the NMR laser (representing a purely temporal system described by the Bloch-Kirchhoff ordinary differential equations) to spatial and spatiotemporal systems, we chose, as a three-dimensional dynamic system, polarized laser beams interacting nonlinearly with sodium atoms. Among other effects, we have observed beam bouncing, beam splitting, and beam switching. This can be well described by partial differential equations for beam propagation derived from the Schrodinger equation and the Maxwell equations. An intuitive explanation is given in terms of intensity and polarization patterns formed by optical-pumping-induced mutual refractive index modifications between polarized resonant laser beams.

Low Frequency Modifications of Seismic Background Noise Due to Interaction with Oscillating Fluids in Porous Rocks

SUMMARY Low frequency spectral modifications of seismic background waves (noise) due to interaction with partially saturated porous rocks are investigated. Non-wetting fluid drops entrapped in pores can oscillate with a characteristic eigenfrequency. A 1D wave equation is coupled with a linear oscillator equation representing these oscillations. The resulting system of equations is solved numerically with explicit finite differences. The background noise is reduced to its dominant frequency (0.1-0.3Hz) which is presumably related to surface waves generated by ocean waves. This frequency is used as the external source. The resulting incident monochromatic wave excites the pore fluid which thereafter oscillates with its eigenfrequency. Oscillatory energy is transferred to the porous rock which leads to an amplitude decay of the fluid oscillation. The elastic matrix carries the eigenfrequency of the fluid oscillation in addition to the external frequency. Fourier spectra of the solid velocity therefore show two distinct peaks: the external frequency and the eigenfrequency of the fluid oscillation. Interestingly, such low frequency modifications of seismic noise are observed above hydrocarbon reservoirs and the presented model is considered as one possible explanation. Time evolution of the amplitude decay of the fluid oscillation seems to be related to the thickness of the porous rock.

Identification of Low Velocity And High Attenuation Zones In Synthetic Seismic Spectra

Summary Hydrocarbon indicating information can be extracted from spectral modifications of the naturally occurring ambient seismic vibration measured at the earth surface. Numerical simulation of wave propagation is applied to investigate the interaction mechanisms between seismic background waves and hydrocarbon reservoirs. In this paper the influence of geological heterogeneities on the surface velocities is investigated. The numerical algorithms are based on explicit finite differences with staggered grids, and solve the elastodynamic equations which are formulated as a first order hyperbolic system. The results of 1D calculations show characteristic peaks in the Fourier spectra of the vertical surface velocity. Those peaks are related to the properties of the heterogeneities and are in agreement with existing analytical solutions. These features are much less pronounced in the 2D case. We assume that this is due to energy loss because of geometric spreading of the waves.

Dynamics of light-pattern formation of polarized laser beams propagating through sodium vapor

The interaction of polarized laser beams and sodium vapor can lead to a variety of intensity and polarization patterns owing to optical-pumping-induced refractive-index variations along and transverse to the beam-propagation direction. While the steady-state behavior has been observed and described in the past, the modeling of the dynamics of the pattern formation processes has become possible only recently. We present the first, to our knowledge, three-dimensional simulations of the dynamics of beam bouncing, beam switching, and beam splitting and the deflection of a laser beam by the inhomogeneous magnetic field of a current-carrying wire. Numerical algorithms used for the calculations and experimental aspects for future observations are discussed.