Panos G. Kelamis

Surface‐related multiple elimination on land seismic data—Strategies via case studies

Three processing strategies for the estimation and subsequent elimination of surface-related multiple energy on land seismic data are presented. They can be applied in a prestack mode (to shot and common-midpoint gathers) or in a poststack mode. The algorithm for the multiple attenuation is based on wave theoretical principles in which the data are used as a prediction operator. The estimated multiples are then adaptively subtracted from the input data to obtain primary-only data. A processing step prior to applying multiple elimination is an important component of these methodologies, particularly in the prestack analysis. Its aim is to regularize the data, improve the S/N ratio, and balance the seismic amplitudes. This results in smooth prediction operators. The effectiveness of these schemes in suppressing multiples is demonstrated with a number of case studies involving processing land seismic data.

Velocity-independent redatuming A new approach to the near-surface problem in land seismic data processing

It is well known that a complex near surface—encountered in areas such as desert, mountainous, and glacial till environments—can significantly distort primary reflections from deeper horizons of interest. This has been and remains a major problem in seismic data processing.

Elimination of land internal multiples based on the inverse scattering series

Despite the explosion of new, innovative technologies in the area of multiple identification and subsequent attenuation, their applicability is mostly limited to marine environments especially in deep water. In land seismic data sets however, the application of such multiple-elimination methodologies is not always straightforward and in many cases poor results are obtained. The unique characteristics of land seismic data (i.e., noise, statics and coupling) are major obstacles in multiple estimation and subsequent elimination. The well-defined surface multiples present in marine data are rarely identifiable in land data. Particularly in desert terrains with a complex near surface and low-relief structures, surface multiples hardly exist. In most cases, we are dealing with so called “near-surface-related multiples.” These are primarily internal multiples generated within the complex near surface.

Over 40,000 vibrator points per day with real‐time quality control: opportunities and challenges

To evaluate high-density source and receiver land seismic acquisition designs, two sets of simultaneous highproductivity vibroseis field tests were performed in a relatively flat terrain area with good signal-to-noise ratio. These included distance separated simultaneous sweeping (DSSS) (Bouska, 2009), slip-sweep (Rozemond, 1996), distance separated simultaneous slip-sweep (dynamic slipsweep) and independent simultaneous sources (ISS) (Howe et al., 2008) with unique sweeps. The second dynamic slipsweep field test used a 29 km active fixed super-spread (12 receiver lines separated by 300 m) with 20 point vibrator fleets on a 25 m x 25 m source grid. A group of 10 point vibrators were oriented orthogonal to the receiver spread in the North and 10 in the South direction with a lateral separation distance of 14.5 km. This method achieved 30,346 vibrator points (VPs) in a 24 hour period. The same fixed active receiver spread was reduced to continuously record two unconstrained simultaneous sources (microseismic mode) in 18 sectors (3x6). Each sector was 1.8 km x 1.8 km with 4,320 VPs on a 25 m x 25 m source grid (77,760 total VPs) with 18 unique 12 s pseudorandom sweeps (Sallas et al., 2008) and repeated with 18 unique linear upsweeps (14.5 s average sweep length) from 5 to 110 Hz. We achieved optimum productivity rates of 45,501 and 44,793 VPs per 24 hours, respectively, with real-time quality control (QC) – we were not sweeping blind. Seventy two drivers were organized in three eight-hour shifts along with four vibrator pushers per shift. Three helped with fleet management and one for TDMA real-time communication between the vibrators and the recorder. Even higher productivity rates could have been achieved with stakeless guidance training of the vibrator drivers and pushers.

Acquisition footprint suppression via the truncated SVD technique: Case studies from Saudi Arabia

An acquisition footprint is noise in 3D seismic data that should be removed prior to interpretation. This paper presents an adaptation of the standard truncated singular value decomposition (TSVD) algorithm that is not only capable of removing random noise, but is actually a very powerful tool for suppressing acquisition footprint artifacts in seismic data.

Focus on land seismic technology: The near-surface challenge

A new era in land seismic is at hand. Growing energy demand will spur greater efforts in exploration and development into regions of the world where hydrocarbons occur in land environments. Interpreters will require accurate near-surface solutions for mapping low-relief structures and stratigraphic traps, and to improve data quality for placing horizontal wells. This will require solutions to near-surface challenges, such as energy penetration, scattering, source-generated noise, surface-generated multiples, statics, and source and receiver coupling. Solutions to these problems will become possible due to advances in seismic acquisition, including simultaneous source acquisition and wireless seismic-driven ultrahigh channel systems. Additionally, advances in seismic processing technology for processing the resulting huge data volumes will be made possible by continual growth in computational capability. These advances will for the first time allow acquisition of true 3D seismic data. This will not only re...

Simultaneous inversion of multiples and primaries: Inversion versus subtraction

In this article, we propose an inversion scheme to replace the adaptive subtraction approaches which are widely used in conventional two-step (prediction + subtraction) multiple elimination methods. This new method, named SIMP (simultaneous inversion for multiples and primaries), inverts seismic data using constraints (e.g., modeled multiples and/or geologic discriminants) for multiples and primaries simultaneously. SIMP incorporates pattern recognition and shaping filters into one concise and practically solvable formulation. Its main advantages are that no orthogonality between multiples and primaries is assumed and that wavelet information is not necessary for the inversion.

Data-driven internal multiple attenuation - Applications and issues on land data

Summary Surface-related and internal multiple elimination schemes, firmly rooted to the acoustic wave equation, have been successfully applied to marine datasets. In land however, the applicability of this type of technology is rather limited. Using the CFP-based, layer-related internal multiple removal algorithm, we propose two data-driven, practical strategies aiming for the estimation and subsequent attenuation of internal multiples on land data. Specific issues and assumptions related to this type of technology with emphasis on land data applications are also considered. The effectiveness of the proposed methodologies is demonstrated with a number of field datasets from the Arabian Peninsula.

Efficient tau-p hyperbolic velocity filtering

Time and offset varying velocity filtering can be achieved by limiting the data input to forward tau‐p transforms. This limiting procedure, called hyperbolic velocity filtering (HVF), suppresses transform‐related artifacts as well as coherent and noncoherent noise while retaining elliptical (reflection) events. We show that HVF can be viewed as a muting process in the slant‐stack domain. Based on this simple but physical interpretation of HVF, a more efficient computer implementation is proposed. We further examine possible applications of HVF for processing seismic reflection data and illustrate the results using both synthetic and real data examples.

Internal multiple reduction in inverse‐data domain

We propose two new methods to attenuate internal multiples in the inverse-data space. The first method involves a datuming step to the top of the multiplegenerating interface. Thus, internal multiples become surface-related and can be removed by a simple muting process. The second method is based on a new theoretical formulation in the inverse-data domain and results in a fully automated, data-driven algorithm. The correctness of both methodologies is verified using synthetic data. These two approaches have been applied poststack on field data, and promising results were obtained.