MULTIPLE‐REFLECTION EVIDENCE

Geophysics ◽  
1948 ◽  
Vol 13 (1) ◽  
pp. 41-44 ◽  
Author(s):  
Joseph C. Waterman
Keyword(s):  
San Joaquin Valley ◽  
Multiple Reflection ◽  
East Side ◽  
Multiple Reflections ◽  
Basement Complex ◽  
Well Data

A rather interesting example of multiple reflections was found in one area in Madera County on the east side of the San Joaquin Valley of California. In this region the top of the basement complex is an excellent reflecting horizon, and the determination of the depth of the basement was confirmed by well data.

DISCUSSION—MULTIPLE REFLECTIONS

Geophysics ◽  
1948 ◽  
Vol 13 (1) ◽  
pp. 57-57
Author(s):  
C. H. Dresbach
Keyword(s):  
San Joaquin Valley ◽  
Velocity Data ◽  
East Side ◽  
Multiple Reflections ◽  
Multiple Events

In various places along the east side of the San Joaquin Valley, roughly thirty miles north of Bakersfield, reflected events have been observed that plotted below the known top of the basement. Sufficient well and velocity data are available to locate them quite closely. From what is known of the character of the basement material, it appears unlikely that the rather smoothly plotting, fairly continuous events could originate from within the basement. The conclusion is therefore forced that they must represent multiple events of some sort.

NOTES ON MULTIPLE REFLECTIONS

Geophysics ◽  
1948 ◽  
Vol 13 (1) ◽  
pp. 55-56
Author(s):  
Dean Walling
Keyword(s):  
Multiple Reflection ◽  
Large Percentage ◽  
Multiple Reflections ◽  
Reflection Theory ◽  
Proper Interpretation

Since the inception of the reflection seismograph, apparent reflections have been observed from time to time, which for one reason or another, do not meet the requirements of normal reflections from interfaces in the sedimentary section. Various theories have served to explain and allow the proper interpretation of a large percentage of these spurious energies. Among these is the multiple‐reflection theory which has proven to be applicable in many cases.

Determination of Dynamic Limits for Rig Heave and Running Speed Based on Drilling Parameters, Well Data and Completion Tool Limitations - Case Studies

2021 ◽  
Author(s):  
Dmitri Gorski ◽  
Martin Kvernland ◽  
Knut Hals ◽  
Margrethe Blaaflat ◽  
Johannes Ladenhauf ◽  
...  
Keyword(s):  
Drill Pipe ◽  
Planning Software ◽  
Drilling Parameters ◽  
Industry Practice ◽  
Novel Method ◽  
Different Depths ◽  
Well Data ◽  
Productive Time

Summary A novel method of utilizing simulations of surge and swab induced by floating rig heave is presented in this paper. The intended applications are in well planning and follow-up of drilling and completion operations. We focus on rig heave during drill pipe connections when the rig's heave compensator cannot be engaged. The method consists of: (1) estimating a dynamic, well- and operation-specific, rig heave limit based on surge & swab simulations at different depths in a well and (2) clearly communicating the dynamic rig heave limit to the rig crew and onshore organization as a simple metric. We present cases where this novel methodology has been tested during the drilling and completion of two offshore wells in Norway, and we elaborate on the operators’ view of the method's advantages. We conclude that complementing the traditional fixed rig-specific heave limit with the dynamic one that is based on the properties of the actual well and the actual drilling/completion parameters offers an opportunity to improve management of risks related to breaching well pressure margins or damaging downhole equipment and to reduce costs through reduction of weather-related non-productive time. We show that the dynamic rig heave limit may differ significantly from well to well and also throughout the same well depending on the kind of operation in the well, depth in the well, well geometry and other parameters related to well and operation properties. Our conclusion is that care should be taken when generalizing a maximum allowed rig heave value as is the industry practice today. The benefits of utilizing dynamic well-specific rig heave limit should be assessed during well planning for any well drilled and completed from a floating rig. Well planning software existing today does not offer this functionality.

Determination of crustal thickness from spectral behavior of SH waves

1969 ◽  
Vol 59 (3) ◽  
pp. 1247-1258
Author(s):  
Abou-Bakr K. Ibrahim
Keyword(s):  
Amplitude Spectrum ◽  
Body Waves ◽  
Multiple Reflections ◽  
Matrix Formulation ◽  
Sh Waves ◽  
Crustal Model ◽  
Amplitude Spectra ◽  
Phase Spectra ◽  
Zero Phase

abstract The amplitude spectrum obtained from Haskell's matrix formulation for body waves travelling through a horizontally layered crustal model shows a sequence of minima and maxima. It is known that multiple reflections within the crustal layers produce constructive and destructive interferences, which are shown as maxima and minima in the amplitude spectrum. Analysis of the minima in the amplitude spectra, which correspond to zero phase in the phase spectra, enables us to determine the thickness of the crust, provided the ratio of wave velocity in the crust to velocity under the Moho is known.

scholarly journals Data-driven internal multiple elimination and its consequences for imaging: A comparison of strategies

Geophysics ◽  
2019 ◽  
Vol 84 (5) ◽  
pp. S365-S372 ◽  
Author(s):  
Lele Zhang ◽  
Jan Thorbecke ◽  
Kees Wapenaar ◽  
Evert Slob
Keyword(s):  
Inverse Scattering ◽  
Computational Cost ◽  
Multiple Reflection ◽  
Data Driven ◽  
Transmission Losses ◽  
Multiple Reflections ◽  
Data Set ◽  
Numerical Examples ◽  
Inverse Scattering Series ◽  
Multiple Elimination

We have compared three data-driven internal multiple reflection elimination schemes derived from the Marchenko equations and inverse scattering series (ISS). The two schemes derived from Marchenko equations are similar but use different truncation operators. The first scheme creates a new data set without internal multiple reflections. The second scheme does the same and compensates for transmission losses in the primary reflections. The scheme derived from ISS is equal to the result after the first iteration of the first Marchenko-based scheme. It can attenuate internal multiple reflections with residuals. We evaluate the success of these schemes with 2D numerical examples. It is shown that Marchenko-based data-driven schemes are relatively more robust for internal multiple reflection elimination at a higher computational cost.

Multiple Reflection Effect on Spin-Transfer Torque Dynamics in Spin Valves with a Single or Dual Polarizer

SPIN ◽  
2015 ◽  
Vol 05 (01) ◽  
pp. 1550003 ◽  
Author(s):  
Weiwei Zhu ◽  
Zongzhi Zhang ◽  
Jianwei Zhang ◽  
Yaowen Liu
Keyword(s):  
Spin Valve ◽  
Spin Transfer Torque ◽  
Multiple Reflection ◽  
Spin Transfer ◽  
Reflection Effect ◽  
Multiple Reflections ◽  
Applied Current ◽  
Negative Current ◽  
Ferromagnetic Layers ◽  
Scattering Matrix Method

In this paper, spin-dependent multiple reflection effect on spin-transfer torque (STT) has been theoretically and numerically studied in a spin valve nanopillar with a single or dual spin-polarizer. By using a scattering matrix method, we formulate an analytical expression of STT that contains the multiple interfacial reflection effect. It is found that the multiple reflections could enhance the STT efficiency and reduce the critical switching current. The STT efficiency depends on the spin polarization of both the free layer and polarizer. In the nanopillars with a dual spin polarizer, the multiple reflections would cause an asymmetric frequency dependence on the applied current, albeit exactly the same parameters are used in all three ferromagnetic layers, indicating that the frequency in the negative current varies much faster than that in the positive case.

SEISMIC VELOCITIES FROM SURFACE MEASUREMENTS

Geophysics ◽  
1955 ◽  
Vol 20 (1) ◽  
pp. 68-86 ◽  
Author(s):  
C. Hewitt Dix
Keyword(s):  
Accurate Determination ◽  
Careful Study ◽  
Seismic Velocities ◽  
Multiple Reflections ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Surface Measurements ◽  
Secondary Objective ◽  
Interval Velocities

The purpose of this paper is to discuss field and interpretive techniques which permit, in favorable cases, the quite accurate determination of seismic interval velocities prior to drilling. A simple but accurate formula is developed for the quick calculation of interval velocities from “average velocities” determined by the known [Formula: see text] technique. To secure accuracy a careful study of multiple reflections is necessary and this is discussed. Although the principal objective in determining velocities is to allow an accurate structural interpretation to be made from seismic reflection data, an important secondary objective is to get some lithological information. This is obtained through a correlation of velocities with rock type and depth.

SPECTRA OF WATER REVERBERATIONS FOR PRIMARY AND MULTIPLE REFLECTIONS

Geophysics ◽  
1972 ◽  
Vol 37 (5) ◽  
pp. 788-796 ◽  
Author(s):  
John Pflueger
Keyword(s):  
Reflection Coefficient ◽  
Seismic Event ◽  
Theoretical Study ◽  
Water Layer ◽  
Multiple Reflection ◽  
Multiple Reflections ◽  
Quick Method ◽  
Sea Floor ◽  
Marine Data ◽  
Amplitude Characteristics

A theoretical study shows that passage of a seismic event through the water‐layer filter imposes amplitude characteristics on the resultant reverberating event which are independent of whether the event is a primary reflection or a multiple reflection. The phase characteristics of each order of event are, however, different. It is also shown that the reverberating sequence from a multiple reflection can be “whitened” by deconvolution but will still exhibit ringing. This phenomenon explains why some marine data, containing dominantly multiple reflections, are not amenable to deringing using standard deconvolution approaches. In addition, a quick method of obtaining the approximate reflection coefficient of the sea floor is derived.

SOME EXPERIMENTS ON MULTIPLE REFLECTION CANCELLATION

Geophysics ◽  
1965 ◽  
Vol 30 (6) ◽  
pp. 1085-1093 ◽  
Author(s):  
Daniel Silverman ◽  
N. R. Sparks
Keyword(s):  
Noise Level ◽  
Multiple Reflection ◽  
Multiple Reflections ◽  
Near Surface ◽  
High Noise ◽  
Precise Information ◽  
High Noise Level ◽  
The Earth ◽  
Primary Signal ◽  
Seismic Records

One of the most promising methods of identification or cancellation of multiple reflections on seismic records involves the calculation of synthetic records with all primaries and multiples, and the matching of the synthetic record with the field record. Such matching suffers today from the lack of precise information about the velocities and densities of the formations, dips of beds nonvertical transmission, etc. One possibility of improving this match involves the use of the earth itself as the “synthetic record computer.” In this process, the upcoming (or downgoing) primary signals are fed back into the earth with a vibrator in proper amplitude and phase to create a synthetic record of multiples only, which should match the multiples on the field record. Of course, only those multiple reflections which include a downward reflection from beds above the primary signal detectors will be included in the synthetic record of multiples only. The paper reports two experimental programs. One was carried out on an analog network to simulate the near‐surface and deeper formations, with means to feed back the upcoming signals in proper timing and polarity to cancel the multiples. These experiments indicated the theoretical workability of the process. The second program of experiments involved the use of a vertical spread to detect the upcoming and downgoing signals, and the use of a hydraulic vibrator to impress those signals back into the earth. These experiments were not conclusive because of insufficient power in the vibrator and high noise level. However, they indicated possible ways in which these limitations might be reduced, and the method applied to routine field operations.

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