John Quigley

Scattered ground‐roll attenuation using model‐driven interferometry

Scattered ground roll is a type of noise observed in land seismic data that can be particularly difficult to suppress. Typically, this type of noise cannot be removed using conventional velocity-based filters. In this paper, we discuss a model-driven form of seismic interferometry that allows suppression of scattered ground-roll noise in land seismic data. The conventional cross-correlate and stack interferometry approach results in scattered noise estimates between two receiver locations (i.e. as if one of the receivers had been replaced by a source). For noise suppression, this requires that each source we wish to attenuate the noise from is co-located with a receiver. The model-driven form differs, as the use of a simple model in place of one of the inputs for interferometry allows the scattered noise estimate to be made between a source and a receiver. This allows the method to be more flexible, as co-location of sources and receivers is not required, and the method can be applied to data sets with a variety of different acquisition geometries. A simple plane-wave model is used, allowing the method to remain relatively data driven, with weighting factors for the plane waves determined using a least-squares solution. Using a number of both synthetic and real two-dimensional (2D) and three-dimensional (3D) land seismic data sets, we show that this model-driven approach provides effective results, allowing suppression of scattered ground-roll noise without having an adverse effect on the underlying signal.

An integrated 3D acquisition and processing technique using point sources and point receivers

Summary An integrated 3D acquisition and processing technique is described. Uncommitted point-source/point -receiver recording is combined with the use of acquisition templates suitable for the generation of appropriately sampled representations of the continuous seismic wavefield, allowing manipulation by data processing methods, including spatial resampling. The method is compared to current industry practice using source and receiver arrays.

Model-based Coherent Noise Attenuation For Complex Dispersive Waves

The attenuation of source-generated coherent noise energy can be a challenging problem for land data where surface waves often exhibit complex behavior with multiple propagation modes, high lateral variability and relatively short wavelengths. The traditional acquisition and processing strategy for mitigation of coherent noise has combined analog spatial filtering through source and receiver arrays in the field, with multi-channel digital filtering in data processing. The field arrays act as complementary spatial anti-alias filters for data processing algorithms which have difficulty in dealing with aliased events. Limitations of the available processing procedures place constraints on the acquisition design which can potentially both limit flexibility and increase the cost of the acquisition. A new model-based approach to sourcegenerated coherent noise attenuation is presented, where the local properties of the multi-mode surface waves are estimated from the seismic data and used to generate a detailed model of surface-wave noise, spatially-variable over the survey area. The method has significant advantages with respect to the handling of aliased coherent noise energy, and robustness to spatial irregularities. The availability of effective processing tools for aliased noise attenuation can have a significant impact on required survey geometry, and on the cost of land exploration.

A comparison of seismic explosives - a case history

Summary A seismic field test is described where comparison shot records were recorded using both a conventional seismic explosive and dBX*. Comparison of te st records on an individual shot basis finds the dBX product more energetic. Though desirable, this is only one aspect to be considered when selecting seismic explosive source parameters. A seismic survey is necessarily made up of a multiplicity of source points. Analysis of the consistency of the seismic data, in both signal and noise content, generated across multiple shot points can provide insight as to how the field data will interact with later data processing work.

A review of nodal land seismic acquisition systems

As the pages of this magazine will attest there is currently much interest in nodal land seismic acquisition systems. The benefits claimed within the marketing materials of such systems are many but just how do they stack up? And with the number of different systems reaching double figures how do they compare? In this article we give a snapshot summary of the various systems available, their relative pros and cons, a comparison with cabled systems and look at the geophysical implications of acquisition system choice.

Acquisition Geometries For Model-driven Interferometric Ground-roll Removal

David Halliday WesternGeco Summary Model approach that takes advantage of a modified seismic interferometry t scattered ground roll from land was data and a novel 2D acquisition geometry. In this abstract we review the existing applications shortcomings of the application to 3D data. We then consider better application Introduction Interferometric on the cross observed at a pair of receiver locations due to a number of appropriately placed sources (Halliday et al., 2010). The result of this correlation and summation process is an estimate of the wavefield at one receiver as if a source had been placed at the ot process can be configured such that the result is dominated by ground roll. Provided located close to a receiver, the resulting estimates can be adaptively subtracted from sourc receiver records. In this abstract, we consider a modification to interferometric input to interferometry by a model of the direct ground roll (Halliday, 2010

Making Waves in the Desert - A Case Study in Sparse Acquisition

al heritage issues these methods are not feasible in the deserts of Australia. In general wide line intervals are preferred and it is highly desirable to avoid straight lines. Even though minimal or no line clearance is performed, the lines are still highly visible on satellite images and on the ground due to compaction by the passage of vehicles. Wide line intervals lead to low fold data but can provide a low environmental impact and still give a reasonable image of the target. However, they often suffer from strong amplitude artefacts commonly known as acquisition footprint. To reduce these artifacts, we deployed sources in a smooth “wavy” sinusoidal pattern and where required, followed natural features in the terrain. This methodology results in both acquisition with a minimal visual impact and provides significant benefits in reducing the acquisition footprint, providing high quality seismic where channel features are clearly visible on the migrated volumes.

Broadband Full-Azimuth 3D Land Seismic Acquisition - Managing 100,000 Channels, Over 20,000 Vibrator Source Points, and 24 Terabytes of Uncorrelated Data per Day

On land, broadband simultaneous vibroseis acquisition methods and high-channel count recording systems provide key technologies for the acquisition of full-azimuth 3D seismic surveys. This paper focuses on the experience gained in the acquisition and processing of two high density source (1,280 and 3,200 VPs/km2) and receiver (640 stations/km2) surveys, and reviews a new high-productivity field test for optimal de-noising.

Meeting the challenge of Mesozoic exploration

The Western Desert of Egypt challenges the exploration for oil and gas both from the reservoir as well as from the surface. The reservoir rocks, Jurassic sandstones and Cretaceous sandstones and carbonates, are often intensely faulted and fractured as a result of the long tectonic history of the area.