Fu, Qiang (M-OSRP, Physics Department, University of Houston) | Zou, Yanglei (M-OSRP, Physics Department, University of Houston) | Wu, Jing (M-OSRP, Physics Department, University of Houston) | Weglein, Arthur B. (M-OSRP, Physics Department, University of Houston)
The Inverse Scattering Series (ISS) internal multiple attenuation algorithm can predict the exact time and approximate amplitude of every internal multiple at all offsets at once. This algorithm does not require any subsurface information and it is model-type independent. When the primaries and multiples are isolated, the ISS internal multiple attenuation algorithm plus energy minimization adaptive subtraction can effectively eliminate internal multiples independent of the the medium model type (e.g. acoustic, elastic, anisotropic, inelastic, etc.). However, when internal multiples are proximal to and/or interfering with a primary, the energy-minimization adaptive subtraction can fail. In proximal /interfering cases the ISS elimination algorithm is needed for predicting the exact time and exact amplitude of multiples, and it would not depend on the energy minimization criteria to fill the gap between attenuating and eliminating the internal multiple. Thus M-OSRP proposed developing ISS internal multiple elimination algorithm to accommodate these proximal/interfering cases. We have an interest in examining the issue of the elimination of interfering internal multiples for increasingly realistic subsurface circumstances. We also recognize the benefit of studying each step of added realism and complexity in isolation. Absorption/dispersion can have a very significant impact on amplitude, often more significant than the acoustic/elastic differences. There is a line of research in the ISS initiative that extends the development and analysis to the absorptive/dispersive world by studying an acoustic absorptive medium. For example, Innanen and Weglein (2003, 2005); Innanen and Lira (2008, 2010); Wu and Weglein (2014). This paper follows that line of contributions and extends ISS internal multiple elimination to absorptive/dispersive acoustic medium, which is the simplest world with an absorptive/dispersive property. We test the current ISS internal multiple elimination algorithm on synthetic data (P-only events) from attenuating medium both analytically and numerically. The analysis and results of the tests show that the current elimination algorithm predicts P-only internal multiple in an absorptive/dispersive medium with both the exact time and amplitude if the absorption/dispersion (finite Q) is only located beneath the generator (which is where the the downward reflection occurs) of the first-order internal multiple, without knowing the medium and its absorptive/dispersive properties. Under this type of circumstances the current ISS internal multiple elimination algorithm is fully effective in predicting accurate P-only internal multiples in an absorptive/dispersive medium. That is positive news for the exploration plays where absorption is only significant below the major internal multiple generators. For instance, that can be the situation for a single absorptive salt body. In this case the major internal multiple generator is often either the water bottom or the top of the salt body and the major attenuation happens within the salt body. Thus the absorption is only existing below the generator, the current acoustic based elimination algorithm is sufficient for predicting an effective P-only internal multiple in this type of exploration play.
Presentation Date: Monday, October 15, 2018
Start Time: 1:50:00 PM
Location: 211A (Anaheim Convention Center)
Presentation Type: Oral
Acquiring lower-frequency seismic data is an industry-wide interest. There are industry reports that (1) when comparing the new and more expensively acquired broad-band lower-frequency data with conventional recorded data, taken over a same region, these two data sets have the expected difference in frequency spectrum and appearance, but (2) they often provide less than the hoped for difference in structural resolution improvement or added benefit for amplitude analysis at the target and reservoir. In Weglein et al. (2016) and Q. Fu et al. (2017), they demonstrate that all current migration and migration-inversion methods make high-resolution asymptotic assumptions. Consequently, in the process of migration, they lose or discount the information in the newly acquired lowest-frequency components in the broadband data. The new Stolt extended Claerbout III migration for heterogeneous media (Weglein et al. 2016) addresses this problem as the first migration method that is equally effective at all frequencies at the target and reservoir. That allows the broadband lower frequency data to provide full benefit for improving structural resolution and amplitude analysis. Q. Fu et al. (2017) provide the first quantification of the difference and impact on resolution for RTM (CII) and Stolt extended CIII. In this paper, we continue to study and quantify these differences in the migration resolution using a wedge model and define the added resolution value provided by the new Stolt extended CIII migration for heterogeneous medium. The side lobes of the images of upper and lower reflectors produce an interference that determines resolution. The migration method with a greater reduction of side lobes will be the migration with a greater ability to resolve two reflectors with a same bandwidth in the data, conventional or band limited.
Presentation Date: Tuesday, September 26, 2017
Start Time: 4:20 PM
Presentation Type: ORAL
Weglein, Arthur (University of Houston) | Mayhan, James (University of Houston) | Zou, Yanglei (University of Houston) | Fu, Qiang (University of Houston) | Liu, Fang (University of Houston) | Wu, Jing (University of Houston) | Ma, Chao (University of Houston) | Lin, Xinglu (University of Houston) | Stolt, Robert (Retired)
There is an industry wide interest in acquiring lower frequency seismic data. There is also an interest in assuring that the broadband data provides added value in processing and interpretation, to better resolve structure and to provide improved amplitude analysis at the target and at the reservoir. There are industry reports that when comparing the new and more expensively acquired broadband lower frequency data with conventional recorded data, taken over a same region, that these two datasets have the expected difference in frequency spectrum and appearance, but they provide little or no difference in structural improvement or added benefit for amplitude analysis at the target and reservoir. The methods that take recorded data and determine structure and perform amplitude analysis are migration and migration-inversion, respectively. There are two objectives of this paper: (1) to demonstrate that all current migration and migration inversion methods make high frequency asymptotic assumptions, that consequently do not provide for equal effectiveness at all recorded frequencies, at the target and reservoir. The consequence is that in the process of migration, they lose or discount the information in the newly acquired lowest frequency components in the broad band data, and (2) we address that problem, with the first migration method that will be equally effective at all frequencies at the target and reservoir, and will allow the broad band lower frequency data to provide improved structure and more effective amplitude analysis. Seismic acquisition and seismic processing must be consistent and aligned to provide interpretive value from broad band data.
The ISS (Inverse-Scattering-Series) internal-multiple attenuation algorithm (Araújo et al. (1994), Weglein et al. (1997) and Weglein et al. (2003)) is the most effective algorithm today for internal multiple removal. It is the only multi-dimensional method that can predict the correct time and approximate amplitude for all internal multiples at once, without any subsur-face information. When combined with an energy minimization adaptive subtraction, the ISS internal-multiple attenuation algorithm can effectively eliminate internal multiples when the primaries and internal multiples are separated. However, under many offshore and onshore circumstances where internal multiples are often proximal to or interfering with primaries, the criteria of energy minimization adaptive subtraction can fail (e.g., the energy can increase when a multiple is removed from a destructively interfering primary and multiple). Therefore, Weglein (2014) proposed a three-pronged strategy for providing an effective response to removing internal multiples without damaging interfering primaries. Currently, there is no capability available in the petroleum industry that addresses that type of serious and frequently occurring challenge. A major component of the strategy is to develop an internal-multiple elimination algorithm that can predict both the correct amplitude and correct time for all internal multiples. The initial idea to achieve an elimination algorithm is developed by Weglein and Matson (1998) by removing attenuation factors (the difference between the predicted internal multiples and true internal multiples) using reflection data. There are early discussions in Ramírez (2007). Based on the ISS attenuation algorithm and the initial idea for elimination, Herrera and Weglein (2012) formulated an ISS algorithm for a normal incident wave on a 1D earth, that eliminate first-order internal multiples generated by the shallowest reflector and further attenuates first-order internal multiples from deeper reflectors. Zou and Weglein (2014) then advanced and extended these initial contributions for the pre-stack and for all first order internal multiples generated at all reflectors. In this paper, we further extend the 1-D elimination algorithm and provide the first ISS multi-dimensional elimination method for all first order internal multiples.
Presentation Date: Tuesday, October 18, 2016
Start Time: 10:45:00 AM
Presentation Type: ORAL
The ISS (Inverse-Scattering-Series) internal-multiple attenuation algorithm (Ara´ujo et al. (1994),Weglein et al. (1997) and Weglein et al. (2003)) can predict the correct time and approximate amplitude for all first-order internal multiples without any subsurface information. When combined with an energy minimization adaptive subtraction, the ISS internal multiple attenuation algorithm can effectively remove internal multiples when the primaries and internal multiples are separated, and not overlapping or proximal. One of issues that the adaptive subtraction is addressing is the difference between the amplitude of the internal multiple and the approximate amplitude of the attenuation algorithm prediction. However, under certain circumstances, both offshore and onshore, internal multiples are often proximal to or interfering with primaries and the criteria of adaptive subtraction may fail, since the energy can increase when e.g., a multiple is removed from an interfering primary. Therefore, in these situations, the task of removing internal multiples without damaging primaries becomes more challenging and subtle and currently beyond the collective capability of the petroleum industry. Weglein (2014) proposed a three-pronged strategy for providing an effective response to this pressing and prioritized challenge. One part of the strategy is to develop an internal-multiple elimination algorithm that can predict both the correct amplitude and correct time for all internal multiples. In this paper, we provide an ISS internalmultiple elimination algorithm for all first-order internal multiples generated from all reflectors in a 1D earth and provide an example from an elastic synthetic data that shows the value provided by the new algorithm in comparison with the value provided by the internal multiple attenuation algorithm.
The ISS (Inverse-Scattering-Series) allows all seismic processing objectives, such as free-surface-multiple removal and internal multiple removal to be achieved directly in terms of data, without any estimation of the earth’s properties. For internal-multiple removal, the ISS internal-multiple attenuation algorithm can predict the correct time and approximate and well-understood amplitude for all first-order internal multiples generated from all reflectors, at once, without any subsurface information. If the events in the data are isolated, the energy minimization adaptive subtraction can fix the gap between the attenuation algorithm prediction and the internal multiples plus, e.g., all factors that are outside the assumed physics of the subsurface and acquisition. However, in certain situations, events often interfere with each other in both on-shore and off-shore seismic data. In these cases, the criteria of energy minimization adaptive subtraction may fail and completely removing internal multiples becomes more challenging and beyond the current capability of the petroleum industry.
A new method to remove internal multiples has been derived under 1D normal incidence. This new method is a step further from the inverse scattering series(ISS) internal-multiple attenuator(IMA) to an eliminator under 1D normal incidence. In the procedure of the method, it constructs the reflection coefficients in order to remove the extra transmission coefficients of the events and then constructs a new function based on the reflection coefficients. This method may be relevant and provide value when primaries and internal multiples interfere with each other in both on-shore and off-shore data under near 1D circumstances. This method does not seek higher order terms in the ISS to construct an algorithm that eliminate first order internal multiples generated by all reflectors.