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Zhou Z.,University of Houston | Hilterman F.J.,Geokinetics Inc.
Geophysics | Year: 2010

Three seismic attributes commonly used to predict pore fluid and lithology are the fluid factor (ΔF), Poisson impedance (PI), and lambda-rho (γρ). We evaluated the pore-fluid sensitivity of these attributes with both well-log and seismic data in Tertiary unconsolidated sediments from the Gulf of Mexico where sand and shale are the only expected lithologies. While the sensitivity of one attribute versus another to discriminate pore fluid is often debated in the literature, the sensitivities of the three attributes are not independent but can be traced back to the fluid factor, which is a function of the P- and S-wave normal-incident reflection coefficients. Interestingly, the fluid factor, which is a reflectivity attribute, at the top of a hydrocarbon-saturated reservoir, is basically independent of the shale properties above the reservoir. It is a function of the brine and hydrocarbon impedances of the reservoir. The next attribute, Poisson impedance, is thenequal to the fluid factor times the sum of the brine and hydrocarbon impedances. Finally, the lambda-rho attribute is equal to the Poisson impedance multiplied by the same impedance sum. Essentially, the same scale factor differentiates these attributes, which does not significantly affect the sensitivity of the attributes. PI is the basis of the sensitivity for these attributes. As a means of testing their sensitivity for predicting pore fluid, we generated the three attributes along with their statistical distributions for different pore fluids for 183 reservoirs. The well-log statistical descriptions were then used to calibrate the seismic amplitude in a 3D survey to reflectivity values, thus allowing pore-fluid classification schemes based on Bayes' decision rules. In essence, seismic-amplitude quantification was based on regional statistics rather than individual wells within the 3D seismic survey to delineate the portions of the reservoir that were saturated with oil, gas, or brine. © 2010 Society of Exploration Geophysicists.


Gaiser J.,Geokinetics Inc. | Verm R.,Geokinetics Inc.
74th EAGE Conference and Exhibition Incorporating SPE EUROPEC 2012 | Year: 2012

Most shear-wave (S-wave) surveys in exploration seismology are acquired with compressional-wave (P-wave) sources. These are primarily for the purpose of recording P to S converted-wave (PS-wave) reflections to image deep oil and gas targets. Essential for processing, is to have a good model of S-wave properties in the overburden and near surface. These properties include not only velocities and statics, but also the presence of S-wave birefringence (splitting) in azimuthally anisotropic media. In addition to PS-waves, pure mode shear-waves (SS-waves) are excited by P-wave sources due to the elastic nature of the near surface and these can aid in velocity model building. The purpose of this presentation is to examine several applications of SS-waves and PS-waves to characterize S-wave properties of the overburden using SS-wave modes from land and marine surveys. Synthetic seismic data from an HTI medium is used to demonstrate that fast and slow SS-waves can be recovered. Also in the marine environment, S-wave resolution is typically very high near the seabed, and can provide accurate S-wave statics and velocities for prestack depth migration (PSDM). An interferometry example shows that SS-waves can be retrieved from OBC data, and a PSDM example illustrates the high resolution that can be achieved with PS-wave data.


Gaiser J.,Geokinetics Inc. | Verm R.,Geokinetics Inc.
74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources | Year: 2012

Early theoretical and field studies showed that P-wave sources generate a substantial amount of shearwave energy for pure-mode (SS-wave) exploration seismology. SV-waves are created in isotropic or VTI (vertical transversely isotropic) media by either buried explosives or surface vibrator and weight drop sources. These methods have not been embraced by our industry; however, benefits could include shallow S-wave velocity model building to help PS-wave processing (CMP processing is easier), and S-wave surface-consistent residual statics. The purpose of this study is to re-examine the feasibility of recovering SS-waves generated by P-wave sources in azimuthally anisotropic media. We analyze 3D synthetic seismograms for VTI and HTI (horizontal transversely isotropic) media to demonstrate the analysis and retrieval of SS-waves. Using conventional PS-wave azimuth processing and analysis techniques, it is possible to recover both the fast and slow SV1- and SV2-waves related to vertically fractured media. Although fast and slow SH1- and SH2-waves are not excited by conventional P-wave sources in the anisotropy symmetry planes, these waves can also be recovered from paraxial azimuths up to ±45 degrees. A field 3D-3C dataset over the Marcellus shale is an ideal test case due to the presence of SS-waves and S-wave splitting.


Gaiser J.,Geokinetics Inc. | Verm R.,Geokinetics Inc. | Chaveste A.,Geokinetics Inc.
SEG Technical Program Expanded Abstracts | Year: 2011

It has been recognized for some time that similar vertical wavelength ranges must be preserved in multicomponent data Garotta and Granger, 1988 and more specifically that wavelengths of P- and C-waves must match in order to sample the reflectivity sequence in an equivalent manner Gaiser, 1996. However, this has not been properly achieved in VP/VS γ analyses as described by Gaiser and Verm 2011 for purposes of registering C-waves to P-wave time Fomel and Backus, 2003 or for joint amplitude versus offset AVO inversion Dariu et al., 2003. © 2011 Society of Exploration Geophysicists.


Pramik B.,Geokinetics Inc.
SEG Technical Program Expanded Abstracts | Year: 2011

Our ability to process and deliver proper broadband seismic data to our colleagues and customers is dependent on the selection of appropriate seismic acquisition parameters. Inadequate survey design can result in insufficient signal to noise ratios in the final data which will lead to an inferior product. Consideration of all seismic events present in the recorded data with respect to proper spatial sampling in all appropriate domains relevant to the seismic processing will help ensure that the broadband signal that is imparted into the earth, detected by the receivers and delivered to the processing center can be faithfully preserved throughout data processing. © 2011 Society of Exploration Geophysicists.


Gaiser J.,Geokinetics Inc. | Verm R.,Geokinetics Inc. | Chaveste A.,Geokinetics Inc.
SEG Technical Program Expanded Abstracts | Year: 2011

The Marcellus shale has become an active area for gas exploration, and has fracture and lithology characteristics that make it a good candidate for multicomponent data. It is well established that similar vertical wavelength ranges must be preserved in multicomponent data and that wavelengths of P- and S-waves must match in order to sample reflectivity in an equivalent manner. Although registration functions align corresponding stratigraphic events of the P-wave and P- to S-wave C-wave reflections, they distort the seismic wavelet because global average velocity properties are independent of local interval properties that define wavelength. In this study we apply a velocity-based wavelet correction method to C-waves, which are expressed as a function of interval and average VP/VS, to match wavelengths of the P-wavefield. Also, we examine the effect of this function for both land and marine data examples and find that land surveys are affected more than marine, and may require spectral broadening of the wavelet. Data from the Marcellus shale in northeast Pennsylvania, shows significant bandwidth improvements for C-waves when wavelet corrections based on velocity match their wavelengths with P-waves. Application of these wavelet corrections should benefit registration fidelity, joint AVO/A offset and azimuth inversions and attribute analyses. © 2011 Society of Exploration Geophysicists.


Gaiser J.E.,Geokinetics Inc.
73rd European Association of Geoscientists and Engineers Conference and Exhibition 2011: Unconventional Resources and the Role of Technology. Incorporating SPE EUROPEC 2011 | Year: 2011

It is well established that similar vertical wavelength ranges must be preserved in multicomponent data and that wavelengths of P- and S-waves must match in order to sample reflectivity in an equivalent manner. Conversion of a wavefield to another time or depth domain is described by transformation functions that depend on average VP/VS ratios and velocity. Although these functions align corresponding stratigraphic events of different wavefields, they distort the seismic wavelet because global average velocity properties are independent of local interval properties that define wavelength. In this study we develop a theory of velocity-based wavelet corrections for domain transformations, which are expressed as functions of interval and average VP/VS and velocity, to match wavelength of multicomponent wavefields. We examine the effects for both land and marine data examples and find that land surveys are affected more than marine, and may require spectral broadening of the wavelet. Data from the Marcellus shale in northeast Pennsylvania, USA, shows significant bandwidth improvements for C-waves when wavelet corrections based on velocity match their wavelengths with P-waves. Application of these wavelet corrections should benefit registration fidelity, joint AVO/A (offset and azimuth) inversions and attribute analyses.


A method for spatial sampling of a seismic wavefield at the bottom of a water layer at an effective spatial sampling denser than the physical layout of the sensors. The sensors comprise a sensing element for vertical particle motion and a sensing element for rotational motion around a horizontal axis. Stress and wavefield conditions allow the rotational sensing element to yield the transverse horizontal gradient of the vertical particle motion wavefield, used in ordinate and slope sampling to yield improved transverse spatial sampling of the vertical particle motion wavefield.


Wang J.,University of Houston | Stewart R.R.,University of Houston | Dyaur N.I.,University of Houston | Lee Bell M.,Geokinetics Inc.
Geophysics | Year: 2015

Marine guided waves are strongly dispersive and commonly observed in seismic surveys worldwide in areas of shallow water with a hard seafloor. They are energetic and can obscure deeper reflection signals. We have conducted several ultrasonic physical modeling experiments to observe marine guided waves. The guided-wave dispersion curves from these surveys fit theoretical calculations very well. We next developed a new method to extract the subbottom S-wave velocity and density from water column guided waves using least-squares inversion. We have also developed a dispersion-curve filter, in the velocityfrequency domain, to attenuate the guided waves. We then applied these techniques to the physical modeling data, which have different water depths and different subbottom materials. The extracted results (S-wave velocity, density, and water depth) match the actual values well. The dispersion-domain filter clarifies reflections by attenuating the guided waves, which benefits further processing and interpretation. © 2016 Society of Exploration Geophysicists.


News Article | November 30, 2016
Site: www.prlog.org

ANCAP and Geokinetics Agree on a Regional Seismic Program, Onshore Uruguay HOUSTON, TX (23 November, 2016) – The Administración Nacional de Combustibles, Alcoholes y Portland (ANCAP) has authorized Geokinetics Inc.

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