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Proceedings Papers

Publisher: American Rock Mechanics Association

Paper presented at the 45th U.S. Rock Mechanics / Geomechanics Symposium, June 26–29, 2011

Paper Number: ARMA-11-388

.... From 45 total strain readings, 38 were less than 50% error, and 27 were less than 25% error. All four methods of attaching the cable were equally successful: epoxy entire length, grout entire length, epoxy ends, and

**wraparound**ends. Further testing should be done outdoors and/or underground...
Abstract

ABSTRACT Laboratory tests of fiber optic strain-sensing cable are presented. The strain-sensing system is Distributed Strain and Temperature (DST) fiber optic cables from Brugg Cable and an Omnisens DITEST fiber optic analyzer. Single lengths of cable were attached to concrete, wood and aluminum beams about 3m long. The beams were forced over wood arches, causing known center deflections. Expected strains were calculated from ideal beam bending equations. Vishay and Micron Optics strain gages were epoxied to the beams and cables to validate the strains. These gages did not validate ideal deflection of the beams. Results proved there is no slip in the Brugg cable, between the glass fiber and the outer sheathing layers. Empirically derived strain coefficients convert Brillouin frequency shift to strain. The cable experienced varying strains along its length, even when attached at the ends only. From 45 total strain readings, 38 were less than 50% error, and 27 were less than 25% error. All four methods of attaching the cable were equally successful: epoxy entire length, grout entire length, epoxy ends, and wraparound ends. Further testing should be done outdoors and/or underground. There is a need for practical cable attachment devices. 1. BACKGROUND Laboratory tests of fiber optic DST cable (distributed strain and temperature) are presented here. A prototype underground installation of the cable is planned for the DUSEL site (Deep Underground Science and Engineering Laboratory) in Lead, South Dakota [1]. Fiber optic sensors, specifically FBG sensors (Fiber Bragg Grating) have been used for structural health monitoring of buildings, piles, bridges, pipelines, and wind turbine blades [2, 3]. DST cables have been field tested for monitoring a bridge [4], casing pipes in oil well construction [5], and settlement during tunnel construction in an urban area [6]. DST cables are also suggested for use in monitoring roads built on ice [7], and in landslide monitoring [8]. FBG sensors are used to measure strain or temperature at a point, DST cable has the advantage of strain monitoring at both large and small scales. These laboratory tests were performed on 3-meter lengths of cable; the DUSEL cables will span several kilometers. The strain-sensing system used here combines DST cable manufactured by Brugg interrogated by an Omnisens DITEST Fiber Optic Temperature and Strain Analyzer. The Brugg cable is designed to prevent slip between the glass fiber and the outer sheathing. The material properties of glass fiber make it an accurate transducer for changes in length. The Omnisens analyzer monitors the Brillouin backscattered light, which is caused by thermally excited acoustic waves in the glass [9]. The frequency shift between the incident light and the Brillouin backscatter is directly proportional to the change in strain [10]. 2. RESEARCH GOAL The goal of the tests was to validate the strain-sensing system: Brugg strain-sensing cable and Omnisens DITEST analyzer. In preparation for an underground installation, the goal was to attach the cable to a rock-like substrate, induce strain and observe and quantify the results. Four attachment methods were employed and compared.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2009 SEG Annual Meeting, October 25–30, 2009

Paper Number: SEG-2009-2944

... to their dips. However,

**wraparound**effects due to spatial aliasing lead to systematic errors in the separation as aliased events map to dips lower than the true ones. This is a major problem of frequency-wavenumber domain implementations especially for 3-D acquisition geometries with large streamer separation...
Abstract

Summary Two methods for dual-sensor wavefield separation are described. First, vector-weighted Kirchhoff datuming provides a stable method for estimating the obliquity factor. This estimate can be used for time-space domain wavefield separation of dual-sensor towed streamer data. As the estimate is obtained from low frequencies only, spatially aliased energy is handled correctly in the separation step. Second, the combination of pressure and vertical particle motion records in Kirchhoff type depth migration yields a ghost-free migrated image. The separation is performed only for that part of the data which is imaged. In this paper, the theory behind both methods is described and the procedures are illustrated using 2-D and 3-D synthetic and field data examples. Introduction Dual-sensor streamer data consists of pressure records and records of the vertical component of particle velocity. The combination of both records yields the separation of the wavefields into up-going and down-going parts (Carlson et al., 2007). The shot-by-shot wavefield separation process is typically implemented as a filter operation in the frequency-wavenumber domain where the seismic events are decomposed according to their dips. However, wraparound effects due to spatial aliasing lead to systematic errors in the separation as aliased events map to dips lower than the true ones. This is a major problem of frequency-wavenumber domain implementations especially for 3-D acquisition geometries with large streamer separation. Whenever the final goal of a survey is to get an accurate image of the subsurface, only a portion of the entire bandwidth usually contributes to the image. The rest, usually the high frequencies, are removed during the imaging step due to limitations in the migration algorithm or to prevent operator aliasing. In principle, wavefield separation could thus be restricted to that portion of the data which is actually used in the imaging step. In this paper, I describe methods to address the aforementioned issues. In the first method, I use an alternative approach for decomposing the data according to the dip of events: vector-weighted Kirchhoff datuming yields an estimate of the obliquity factor as a function of space and time. This is analogous to the application of multiple weights in Kirchhoff-type depth migration as described by Bleistein (1987) and Tygel et al. (1993). The obliquity factor estimate can be used directly for wavefield separation as the frequency-wavenumber domain filter translates to the ratio of acoustic impedance and the obliquity factor in the time-space domain. The datuming steps are implemented in the space domain and, thus, allow for smooth receiver depth variations and moderate irregularities due to streamer feathering. The theory takes velocity variations at the receiver level into account (within the validity range of the high frequency approximation). The obliquity factor estimate is derived from the low frequencies which are not spatially aliased but is used to scale the entire bandwidth of pressure and vertical particle velocity records in the wavefield separation. Consequently, spatially aliased energy is scaled correctly in the separation process.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2008 SEG Annual Meeting, November 9–14, 2008

Paper Number: SEG-2008-2132

... that for a single reflecting horizon, or a set of nearby horizons, the effects of temporal

**wraparound**can be neglected. The output of this process is a migrated image of the target structure showing illumination effects due to overburden velocity structure and acquisition sampling. Introduction It is often...
Abstract

Summary Seismic illumination can be predicted using one-way wavefield extrapolators and formulations for forward modeling and migration. Rather than compute a finely sampled set of frequencies over the bandwidth of interest, I compute only a decimated set of frequencies and rely on the fact that for a single reflecting horizon, or a set of nearby horizons, the effects of temporal wraparound can be neglected. The output of this process is a migrated image of the target structure showing illumination effects due to overburden velocity structure and acquisition sampling. Introduction It is often useful to be able to study how accurately a seismic survey geometry images a hypothetical target reflector. Think of the process of modeling a seismic survey over a volume of the subsurface followed by processing that modeled data to make an image of the reflectors in that volume of subsurface as a "system". Heuristically, we can define seismic "illumination" to be the transfer function of that system. Historically, ray tracing methods provided an inexpensive approach for studying the illumination of a target reflector surface in a seismic experiment. When the overburden and the target are relatively simple, ray-traced hit-count methods are often sufficient to predict seismic illumination. The ray-based method can be improved by using a boundary integral modeling formulation to deal with diffractions and more complex reflector surfaces. However, when the overburden velocity is complex, e.g. in the case of subsalt imaging, raytracing methods will likely fail to give accurate estimates of how well a seismic experiment images a reflector. Full finite-difference modeling and subsequent processing/imaging is considered to be the "gold standard" for studying seismic illumination. Waves propagate in all directions, all orders of multiples are generated (if desired), and amplitudes are consistent with the acoustic wave equation, including transmission losses and reflection coefficients. Although relatively complete, the demands of a full finite-difference modeling project are such that even today, they are not carried out on a whim. Typically both velocity and density models must be constructed, the surfaces and bodies used to do this must be carefully QC''d; run times are long enough that such a project cannot be viewed as a "throwaway". Thus, there is a use for a waveequation based method for modeling the response of the seismic experiment on a target reflector surface that is more accurate than raytracing, and less expensive/demanding than full finite-difference modeling. Wave equation modeling with one way Green''s functions One-way wave equation modeling is usually a less expensive alternative to full 2-way time or frequency domain finite-difference modeling. This sequence approximates the process of recording seismic data in the field and processing it to make an image. Here, the Green''s functions for the migration step do not have to be the same as those in the modeling step. In the modeling step we may wish to incorporate effects such as transmission loss at discrete boundaries, where as in the migration step we may wish to include amplitude compensation terms commonly used when migrating real data.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2008 SEG Annual Meeting, November 9–14, 2008

Paper Number: SEG-2008-2512

...

**wraparound**artifacts and (2) Fourier spatial interpolation does nothing whatsoever to reduce aliasing artifacts. Introduction The fundamental principle of surface-related multiple prediction is that the upcoming energy recorded at any given trace location in a shot produces a downgoing reflected...
Abstract

Summary In this abstract I compare theoretical and practical aspects of the Delft and the Inverse Scattering surface-related multiple attenuation approaches. I first show the essential theoretical equivalence of the two using a simple three line mathematical argument. After that I look at similarities and differences in the implementation of the two methods, from deghosting, obliquity and antialiasing, to memory requirements and out-of-core pipelining, and finally comparing their relative computational cost. Of particular note, I show that (1) no spatial FFT padding is required to suppress wraparound artifacts and (2) Fourier spatial interpolation does nothing whatsoever to reduce aliasing artifacts. Introduction The fundamental principle of surface-related multiple prediction is that the upcoming energy recorded at any given trace location in a shot produces a downgoing reflected signal that is a secondary source whose response can be predicted by convolving that trace with a suitably tailored shot record whose shot position is at that given trace location. Because this basic convolution implicitly squares the source spectrum, deconvolution is used to flatten the source spectrum so that its square remains flat over the bandwidth of the data. Of course, additional adaptive shaping is needed to fine tune the imperfectly predicted multiples. Interpolation and extrapolation of the input data to fill in missing inner offsets is a necessary preprocessing step. In addition to attenuating edge effects, this step accounts for the fact that in a horizontally layered earth multiples at offset 2h arise from primaries at offset h. In addition, it is generally helpful to interpolate each shot record 2:1. This last preprocessing improvement is due to Bill Dragoset (pers. comm.) who notes that the convolution will take two dips p and q and turn it into a steeper dip p+q. Since the multiple estimate involves summation across such convolved traces, sufficiently aliased energy will stack in as background fuzz. By preinterpolating 2:1, an original dip of p msec/trace now becomes 1/2 p instead, supressing its contribution to aliasing. Deghosting is generally needed to separate the up and downgoing shot and recorded traces. This operation depends upon the source and receiver depths and the angles at which the seismic energy arrives at the surface. An obliquity correction can be applied at the same time as deghosting if done in the Fourier or ? p domains. The cosine obliquity term compensates for the difference between amplitude and energy. Theory Let us initially assume that we have arranged our shots and receivers on a common grid, with the shot and receiver spacings both equal to the grid spacing. After a temporal Fourier transform to constant frequency slices, a nice way of visualizing the basic Delft (Verschuur, et al. 1988) operation of predicting multiples, M, is as a matrix multiplication of a data matrix, D, and a proxy primary matrix, Q, which is typically the input data itself or the output of a previous demultiple iteration.

Proceedings Papers

Publisher: NACE International

Paper presented at the CORROSION 2006, March 12–16, 2006

Paper Number: NACE-06263

... ultrasonic guided waves on pipe or tubes, a

**wraparound**transducer typical of that illustrated in Figure 2 can be used. A variety of different sensor types could be considered for a particular tube diameter including for example piezoelectrics, electromagnetic acoustic transducers, magnetostrictive sensors...
Abstract

ABSTRACT Inspection from a single probe position for corrosion detection in tubular structures and pipe is discussed. The range can be 5 feet on to several hundred feet depending on tubular conditions of insulation, coatings, or environment. Several new focusing systems are presented and compared with currently available axisymmetric instrumentation. Focused systems are more sensitive, have greater penetration power, and also reduced false alarm rates. INTRODUCTION The possibility and benefits of using long range focused ultrasonic guided waves for corrosion detection in tubular structures are discussed. Ultrasonic guided waves are being used more frequently for inspecting pipelines over a long distance from a single probe position because of inspection simplicity and reduced cost. One benefit of guided wave inspection is the complete coverage of a tubular structure over a long distance, opposed to more traditional point by point bulk wave propagation inspection. Guided wave propagation occurs when boundaries are involved. As an example, see Figure 1 showing a few possibilities of guided wave propagation. Many structures that exist in our infrastructure are actually natural waveguides. A few are listed in Table 1. The utilization of guided waves in natural wave guides and structures with boundaries will become more commonplace in the future primarily because of the advancements made in guided wave understanding in the last decade or so. In order to carry out an inspection using ultrasonic guided waves on pipe or tubes, a wraparound transducer typical of that illustrated in Figure 2 can be used. A variety of different sensor types could be considered for a particular tube diameter including for example piezoelectrics, electromagnetic acoustic transducers, magnetostrictive sensors, and others. Basic elements of wave propagation can be found in Rose where the basic concepts of dispersion curve analysis and wave structure so essential to guided wave analysis are presented in detail. A variety of other research papers presented by the Rose group on the development of ultrasonic guided waves in piping over the past decade or so is outlined in references. One of the first practical ultrasonic guided wave inspection systems is reported in for thin-walled steam generator tubing. The long distance inspection from a single sensor position was realized in this work. The problem of studying the applied surface tractions to produce guided waves with various sensor types is reported in [3] and [4]. The possibility of considering water loading in tubing is reported in [5]. Recent work comparing longitudinal versus torsional waves is also discussed in several of the papers. See [9] for example. Utilization of non-axisymmetric or flexural modes required to produce the focusing of ultrasonic guided waves is also reported in many of the references; see for example [6] and [7]. The concept of an ultrasonic phased array around the circumference of a pipe to achieve focusing is reported in [8]. The phased array approach is popular today for bulk waves and is now reported for guided waves as well. A general discussion of the focusing technique and the problems associated with coated pipes is reported in [9] and [10]. The utilization of the flexural torsional mode along with the flexural longitudinal mode and natural focusing schemes are reported in references [6-7], [13]. TABLE 1- NATURAL WAVEGUIDES FIGURE 1 ? Guided Wave Possibilities; a. Rayleigh (surface) wave schematic, b. Stonely wave schematic, c. Lamb wave schematic, FIGURE 2 ? Typical wrap around sensor system for pipe inspection?sensors can be piezoelectrics, an electromagnetic acoustic transducer or other. Sensors can be longitudinal or t

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 1998 SEG Annual Meeting, September 13–18, 1998

Paper Number: SEG-1998-1925

... ABSTRACT No preview is available for this paper. seg 3D Spectral reverse time migration with no-

**wraparound**absorbing conditions Ernesto Bonomi, Leesa Brieger, Carlo Nardone, and Enrico Pieroni, Geophysics Area, CRS4 Summary Comparative studies of methods of reverse time migra- tion...
Proceedings Papers

Publisher: Society of Petroleum Engineers (SPE)

Paper presented at the SPE/IADC Drilling Conference, March 15–18, 1987

Paper Number: SPE-16122-MS

... operations. The design features of the new ISWE which directly correspond to flanged equipment are: The tubing load is transferred to the casing head body. The production casing is enclosed with an externally testable O-Ring seal. The internal components such as the stripper rubber,

**wraparound**...
Abstract

Abstract The purpose of this paper is to illustrate the benefits of a new wellhead design which is a variation of the independent screwed wellhead equipment (ISWE) presently on the market. The design offers most of the performance characteristics of low pressure flanged equipment up to 3000 psi, but at a substantial initial cost savings. The application is for moderate depth wells and/or Enhanced Oil Recovery (EOR) fields, that have limited flowback potential. Introduction Declining oil prices have dictated that we search for cost saving alternatives in wellhead equipment while maintaining those performance features primarily associated with safety during drilling, running casing and subsequent completion/remedial work. This means having a wellhead with the depth and pressure rating of flanged equipment, while offering dependable methods of controlling pressure during most operations. The design features of the new ISWE which directly correspond to flanged equipment are: The tubing load is transferred to the casing head body. The production casing is enclosed with an externally testable O-Ring seal. The internal components such as the stripper rubber, wraparound hanger, and mandrel tubing hanger will pass through the blow out preventers (BOP) and are held in place byhold-down screws. The wellhead is connected to the BOP by means of a flange which allows testing of the BOP stack up to 3000 psi. The design lends itself to applications in Enhanced Oil Recovery (EOR) fields because the elastomer in the system which would be most affected by chemical actions of CO2-H2S-Water may be changed easily during workovers by removing the tubing head from the well. Discussion The traditional ISWE and the new ISWE design are shown in Figure 1. Both bodies are forgings with a Rockwell C hardness of 14-22 suitable for H2S service. This hardness range is the same for all of the manufacturers' equipment. It has a lower profile and eliminates any exposed casing between the casing head and tubing head. The tubing head is equipped with two elastomer O-Ring seals and a test port in order to pressure test the seals. In addition to standard slips, the tubing head can accept a wrap around or mandrel type tubing hanger which is interchangeable with other products from this manufacturer. P. 623^

Proceedings Papers

Publisher: Offshore Technology Conference

Paper presented at the Offshore Technology Conference, May 5–8, 1980

Paper Number: OTC-3809-MS

... produces a "wide band" stationary phase record in time, which shows the correct move out and amplitude variation of the reflections with offset. This time domain method allows arbitrary offset distances and there is no

**wraparound**in time and distance on the final profile, two common problems in frequency...
Abstract

ABSTRACT A 2-D point source seismogram is described which calculates marine profiles of reflections from a sequence of flat layers. The seismogram is expressed as a sum of plane wave reflection responses of the layers over a wide aperture of incident angles from the source. Each plane wave response is computed in the discrete time domain using a new recursion formula. The solutions include primaries, multiples, and all conversions between P and SV waves at the layer interfaces. Critical angle reflections and transmissions are included for propagating waves, but evanescent waves are not calculated. Each trace of the profile is obtained by delaying and summing the plane wave components over the spectrum of incident angles from the source. The time delay for each component equals the trace offset distance from the source divided by the horizontal phase velocity of the component. The summation produces a "wide band" stationary phase record in time, which shows the correct move out and amplitude variation of the reflections with offset. This time domain method allows arbitrary offset distances and there is no wraparound in time and distance on the final profile, two common problems in frequency-wavenumber methods which use the 2-D FFT. The truncation of the incident angular spectrum to include only reflections causes some precursor energy as in the frequency-wavenumber solutions. This effect can be minimized by properly sampling and tapering the angular spectrum of plane wave components before summation. INTRODUCTION In this paper we describe a new method for generating synthetic marine seismograms by summing up the plane wave components directly in time over a spectrum of take off angles from the source. The technique is a variation of the reflectivity method for computing the reflected P and SV waves in a multilayered medium. The purpose of the method is to calculate only the reflection response of the layers and omit the surface waves, which are often removed by signal processing methods in real data. For a 2-D point source the plane waves are summed over a range of real incident angles from -90 to +90 degrees. By neglecting the imaginary angles, which are used to synthesize the surface waves, the calculations are made simpler with no loss of information in the reflected phases, which are crucial in exploration. A recent paper which does this synthesis in the frequency domain is by Kennett (1979). In the 3-D problem the angular summation is also done over azimuthal angles. Fertig and Muller (1979) used this method to show that strong P to SV conversions occur for wide angle reflections from coal bed seams. The plane wave components in this paper are calculated by a new layer recursion in discrete time which is adapted from a frequency domain recursion given by Kennett (1979). The recursion begins with the reflection response of the deepest interface of the model and progresses up through the layers to the free surface. In the recursion described below, 2 × 2 matrix filters in powers of (available in full paper) are used to propagate elastic waves through the layers. This discrete time approach to coupled P and SV waves was first given by Frasier (1970) in a reference we shall call Paper 1. Another plane wave synthesis of 2-D seismograms was presented by Aminzadeh and Mendel (1978). They used some results from Paper 1 to recast the wave propagation in terms of state-space models. In contrast to the recursive filter approach to wave propagation, the state-space method uses matrices which grow in dimension with the number of layers utilized, and requires a ray tracing scheme to keep track of the interface reflections and transmiss

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 1988 SEG Annual Meeting, October 30–November 3, 1988

Paper Number: SEG-1988-1258

... Wang, Univ. of Calgary, Canada SUMMARY The method works in the time domain. In this way, all the artifacts associated Image processing techniques have with frequency domain methods, like ringing

**wraparound**effects as in F-K filtering are recently been applied to seismic data for not present...
Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 1984 SEG Annual Meeting, December 2–6, 1984

Paper Number: SEG-1984-0786

... ABSTRACT No preview is available for this paper. frequency interpolation interface continuation reflector model wedge

**wraparound**ray reference velocity reservoir characterization source position forward modeling fourier transform depth migration propagation inverse...
Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 1985 SEG Annual Meeting, October 6–10, 1985

Paper Number: SEG-1985-0526

... ABSTRACT No preview is available for this paper. time-domain correlation time domain

**wraparound**correlator sequence relative computational speed fourier transform accuracy frequency-domain correlation reservoir characterization correlation cyclic convolution data quality...
Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 1995 SEG Annual Meeting, October 8–13, 1995

Paper Number: SEG-1995-0192

...) recursive algorithm for time migration. We use Levin s

**wraparound**filter (Claerbout, 1985) in order to parallelize over temporal frequencies. We have applied a variety of optimizations including emphasizing scalar (rather than vector) temporaries in loops, converting to 32-bit data types, and using...
Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 1994 SEG Annual Meeting, October 23–28, 1994

Paper Number: SEG-1994-0684

... root (DSR) equation in common midpoint and offset coordinates for prestack migration produces notable artifacts that are routinely attributed to Fourier domain

**wraparound**in the offset wavenumber space. These artifacts usually pre- clude the use of DSR for separate common-offset sections. I show...Journal Articles

Journal:
SPE Production & Operations

Publisher: Society of Petroleum Engineers (SPE)

*SPE Prod & Oper*13 (02): 109–117.

Paper Number: SPE-37436-PA

Published: 01 May 1998

... to 24°API oil production. An Accuflow System was selected in place of another conventional test separator. The multiphase-metering system has a

**wraparound**design, as shown schematically in Fig. 4, and uses a 1-in. Rosemount vortex meter to measure the gas flow and a 1-in. Micro Motion meter (Model...
Abstract

Summary This paper describes the evaluation results on the measurement accuracy and long-term operation of a multiphase meter used for well testing. The test was conducted by Chevron at its Lost Hills Field in California. After many years of development work, several multiphase meter manufacturers have begun to offer their meters commercially for production operation. In this paper, commercial multiphase meters are first reviewed briefly based on the methods that those meters use to handle the fluid flow. The multiphase meter selected for this application was manufactured by Accuflow Inc. This commercial multiphase meter uses the compact separation approach in handling the oil/gas/water flow stream by first separating the gas from the liquid stream and then measuring the gas and oil/water separately. The Accuflow system was installed at a gauge station in January of 1996. It was designed to test wells that have productions ranging from about 100 to 400 barrels of fluid a day, high water cut (40% - 90%), and up to 200 MCFD of gas. For accuracy testing, the multiphase meter was piped in series with a test separator at the gauge station. Production from selected wells, covering a wide range of flow rates, water cuts, and gas volume fractions, flowed through the multiphase meter first and then the test separator, enabling comparison of the new meter's performance and accuracy with an existing reference. Additional tests were also conducted to compare results with a test tank at the site. The paper also discusses other operational aspects of the multiphase meter such as equipment maintenance and sand accumulation. Overall, satisfactory performance of this multiphase meter was observed and additional units are being installed at Lost Hills Field. Introduction It is well known that direct measurement of multiphase (oil, gas and water) production flows would offer potentially large savings in facilities and operating costs. The main saving comes from the elimination of test or bulk separators and associated hardware and maintenance for the production fluid. In the offshore environment, not requiring separators has the added benefit of reducing space and weight requirements of a platform, resulting in further savings. The subsea version of multiphase technology (pumping and metering) is believed to offer an even greater saving by eliminating the need for test lines or even a platform and thereby enhancing the economics of some marginal fields. One such economic analysis can be found in Reference 1. Thus, many organizations engaged in petroleum production research, especially among North Sea operators, began to study and develop solutions to this problem in the mid-'80s. Accurate measurement of multiphase flows is a complex task due to the number of unknowns involved. Up to five parameters need to be measured in order to characterize an oil-gas-water flowing stream. There are the three velocities (one velocity for each phase) and two phase fractions inside the pipe (the third phase obtained by difference). In addition to the five unknowns (reduced to three in the case of a homogeneous flow), the flow conditions that are likely to be found at a multiphase flow meter tend to further complicate the measurement process. The major complicating factor is the prevailing flow regime. A fluid comprising liquid and gas phases can assume a wide variety of flow regimes depending on the process condition under which it operates. This varying flow pattern is not a concern in single phase flows. The flow pattern is primarily governed by the fractions, physical properties, and velocity of each phase present at the meter installation as well as the piping configuration (e.g., pipe diameter, inclination angle) and orientation (e.g., vertical or horizontal). Despite these formidable difficulties, significant progress has been made in multiphase meters after a decade of product development work. A few metering schemes finally emerged as viable products and some vendors have begun to market their multiphase meters for commercial use.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 1991 SEG Annual Meeting, November 10–14, 1991

Paper Number: SEG-1991-1343

... as a standard slant stack except that some p traces have a high cut filter applied. The advantage for inversion of the modified slant stack is that each point in the (K, F) diagram is picked out by only one radial line. The confusion in the standard slant stack is caused by the

**wraparound**which means that each...
Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2007 SEG Annual Meeting, September 23–28, 2007

Paper Number: SEG-2007-2344

... of 3D Kirchhoff migration Figure 7: Kirchhoff migration impulse response using the three-filter cascade approach (displayed with a huge gain 200 db) show the pres- ence of the beams of noise associated with frequency domain artifacts of the cascaded filters (

**wraparound**). in a better frequency response...
Abstract

INTRODUCTION SUMMARY Since 3D Prestack Kirchhoff Depth Migration (KPSDM) has become one of the leading imaging tools for hydrocarbon exploration, its accurate and precise handling of the kinematical and dynamical aspects of the wavefield have become center stage to the R&D efforts worldwide. In a separate paper in this proceeding by the same author, describe a modified antialiasing filter weight that corrects for amplitude artifacts observable in earlier designs. Here we continue the efforts of developing an efficient true amplitude migration algorithm by suggesting a simplification of the traditional filtering done during this process that will improve the performance and precision of the results. In most Kirchhoff migration implementations, a triangular smoothing filter is used to avoid high frequency aliasing along the migration operator. This filter is implemented in three steps: causal integration, anti-causal integration, and Laplace-type differentiation along the diffraction stacking surface. In addition a derivative filter (known as r–filter) is applied to the input data to correct for the wavelet phase rotation introduced by the Kirchhoff summation. We will find that the standard filtering sequence of applying the r–filter, causal integration, and anti-causal integration can be replaced by just an anti–causal integration. Kirchhoff migration provides one of the best imaging solutions when data are non-uniformly distributed in space. It also is fast and flexible when it comes to input/output geometries. In our quest to make 3D KPSDM better and faster we have found an alternative to achieve a comparable result by replacing the traditional filtering sequence made of a r–filter, causal integration and anti-causal integration with a single anti-causal integration filter. Note that this is applicable to time as well as depth migration algorithms. Before the data are stacked along a diffraction surface, they are filtered for waveform phase shaping and pre–filtered in preparation for the antialiasing operation applied during summation. Since the integration process shifts the waveform shape, the r–filter works restoring it. The anti-aliasing filter is applied in three stages: causal integration, anti-causal integration and then a Laplacian computation rolling along the stacking diffraction surface. By replacing these three filters by an anti-causal integration the performance and accuracy of the algorithm can be greatly improved. The results presented here also incorporate the normalization factor in the anti-aliasing filter mentioned above and described elsewhere in these proceedings. These corrections eliminate azimuthally anisotropic amplitude behavior on the migration impulse response as well as amplitude distortions with time and offset, introduced by the traditional scaling factor in Lumley et al. (1994) and Abma et al. (1999). THREE FILTERS IN ONE Differentiation in the frequency domain can be accomplished by a multiplication by -iw, where w represents the circular frequency, and D t is the temporal sampling rate. As the sampling rate D t goes to zero the approximation becomes an equality. From this it is straight forward to conclude that the three filters: r–filter, causal integration and anti-causal integration should be equivalent to just an anti-causal integration.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 2014 SEG Annual Meeting, October 26–31, 2014

Paper Number: SEG-2014-1295

... to a factor of two, corresponding to a 60° maximum propagation angle. To implement the phase-shift with few artifacts, we used the operator dip control of Levin (1983) to suppress

**wraparound**. For constant velocity, the relevant limits for p = |k and aperture radius r are (3) = " 1 and (4) = 4 , where...
Abstract

Summary Shallow Subsurface Radar (SHARAD) data from the Mars Reconnaissance Orbiter are acquired approximately 300 kilometers above the Martian polar icecap. In this report we detail how to adapt seismic 3D poststack downward continuation to allow construction of the data that would have been recorded a short distance above the Martian surface, thereby saving significant computational time and storage in subsequent imaging and analysis of the shallow polar subsurface. Introduction At the 2013 ProMAX®/SeisSpace® User’s Group in Highlands Ranch, coauthor Fritz Foss introduced the audience to a Mars radar dataset that he intended to image using seismic processing and imaging tools. One of the questions he raised was whether the SeisSpace/ProMAX software package provided him the ability to redatum those data from orbital heights around 300 km to near-surface altitudes around 1 km. Dr. Levin thought that there was already such an option in the 3D FK migration package, but if there wasn’t, he’d cobble together a quick one. Well, there wasn’t, so he did, though not so quickly.

Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 1984 SEG Annual Meeting, December 2–6, 1984

Paper Number: SEG-1984-0627

... in the applica- tion of discrete solution methods to wave propagation prob- lems is the presence of reflections or

**wraparound**from the boundaries of the numerical mesh. In this paper we describe a scheme for the elimination of these unwanted events which can be applied to a wide class of wave equations...
Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 1984 SEG Annual Meeting, December 2–6, 1984

Paper Number: SEG-1984-0784

... Gazdag s phase-shift-plus-interpolation (PSPI) method is modified to compute stacked profiles based on the exploding reflector model. A point scatterer model is used to illustrate the

**wraparound**problem caused by the use of Fourier transforms and how the effect can be suppressed by absorb- ing energy...
Proceedings Papers

Publisher: Society of Exploration Geophysicists

Paper presented at the 1990 SEG Annual Meeting, September 23–27, 1990

Paper Number: SEG-1990-1578

.... Hence an expression for the filter is ~-2niIhl PlP)/10~ (10) Figure 2 shows the result of applying this filter to a wavelet in a single column in a 48 x 48 m versus s sectfon. Note that a wavelet is spread along a parabola but the

**wraparound**creates a noisy 3ackground. This noise can be attenuated...Advertisement