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TechLink

TechLink is a Technical e-newsletter written by the technology and R&D groups in PGS Geophysical. Each month TechLink will highlight key PGS technology developments and applications, covering our complete breadth of products and services.

Listed below are the recently published TechLinks. To sign-up to receive TechLink, click here.

TL #52: Marine Source Modeling and Wavelet Analysis in Nucleus+

PGS has extended the capabilities and scope of the Nucleus modeling package to a new platform known as Nucleus+. A project-based and project sharing capability is now offered, enabling greater flexibility and easier user access to libraries of results and files. A new tree structure during parameterization provides greater interactivity and the capability to execute several jobs in a workflow or batch manner. A “job builder” enables easier modification and revision later during projects. Read more

TL #51: 3D Beam Prestack Depth Migration

In 1999 AGS (now part of PGS) started development of Beam Pre-Stack Depth Migration (BPSDM). The anticipated merits were simplicity, economy, flexibility and future development possibilities. The unknowns were the migration accuracy and quality. Read more

TL #50: Radon Transform Demultiple

The sheer variety of multiple removal techniques is a testament to the importance and complexity of the demultiple problem in seismic processing. Perhaps the most widely used class of techniques over the past of couple of decades has been those based on the Radon transform. These methods, based on differences in moveout between primary and multiple events, have evolved over the years and continue to improve to the present day. Read more

TL #49: North Sea Lower Cretaceous

This study has used the laterally-extensive PGS CNS (Central North Sea) MegaSurvey 3D seismic volume and all relevant released exploration and appraisal wells (over 1,200 wells) to create a systematic seismo-stratigraphic model for the Lower Cretaceous over some 34,000 km2 of the Central North Sea; spanning the Moray Firth, Witch Ground Graben, South Halibut Platform, East and West Central Grabens. Read more

TL #48: Advanced Multiple Elimination

In Wintershall’s onshore concessions in the Libyan Sirte Basin the main challenges in processing seismic data are the attenuation of severe noise, high-amplitude surface related multiples and internal reverberations that are interfering and partially masking the primary signal. The application of pre-stack depth migration is vital to obtain the best structural image. Read more

TL #47: Seismic Regularization

PGS has a comprehensive toolkit of regularization and interpolation technology that will help improve the imaging of all types of data and, in the case of 4-D data, the repeatability between data vintages. Read more

TL #46: Ramform Sovereign

The history of the Ramform seismic vessel design begins with the Norwegian Navy surveillance ship Marjata in the early 1990s. The PGS engineers drew the conclusion that Marjata’s wide stern made her perfect for seismic acquisition where it is desired to have as little noise as possible from the vessel itself during data acquisition. Read more

TL #45: Innovations in Marine Operations

PGS has developed two significant towed source and streamer technologies. Both are now in the early stages of full-scale production deployment, and are expected to gradually be rolled out across the PGS fleet. Read more

TL #44: Improving the PSDM image by efficient velocity volume editing

By addressing localized velocity anomalies in the shallow area of a 3D seismic volume, the imaging below the anomalies can be significantly improved. These improvements will then have a direct impact upon the interpretation of the data set. Read more

TL #43: MTEM

Multi-Transient EM (MTEM) is a proven remote sensing method for direct hydrocarbon detection and delineation. Profiles are rapidly derived to describe the resistivity of the earth, spatially correlated with the structural information provided by seismic data. Hydrocarbon fluids and gas can thus be discriminated in terms of location and saturation – prior to any drilling decisions. (5.8 MB) Read more

TL #42: Crystal WATS Processing Strategies

Wide Azimuth Towed Streamer (WATS) seismic has found increasing commercial application on a large scale in recent years. WATS exploits acquisition geometries of increased effort and complexity in comparison to “conventional” 3D surveys, but the benefits delivered typically far outweigh the increased costs, particularly in areas where seismic imaging complexities have previously proven insurmountable. (6.8 MB) Read more

TL #41: GeoStreamer

PGS has been developing an entirely new towed marine streamer concept for about five years. The project objective was to engineer a streamer that is capable of recording both the scalar pressure field and the vertical component of the vector particle velocity field. (1 MB) Read more

TL #40: Reverse Time Migration

Reverse Time Migration (RTM) is a sophisticated wave equation depth migration method that has recently become achievable for large 3D surveys because of advances in computational power and clever programming. (1.5 MB) Read more

TL #39: Source Measurements

In July 2006 PGS conducted a new series of farfield signature measurements of single air guns and two-gun clusters in cooperation with the main vendors of marine seismic air guns; Bolt Technology Corporation and Sercel. The main objective of this project was to perform measurements of new guns for NUCLEUS source modelling calibrations. (400KB) Read more

TL #38: Migration Scanning

The traditional method of migration scanning for velocity analysis has been updated and modernized for use in sub-salt wave equation processing. A new set of tools along with an efficient methodology have been developed at PGS to accurately determine the velocity in these difficult areas. (900KB) Read more

TL #37: Infill Management

A method for efficiently modelling the effects of coverage holes in migrated data is presented. It is shown that the modelling predictions are in good agreement with the effects observed in real data. The modelling is performed as part of presurvey planning, and the results used to assess infill requirements based on permitted levels of data degradation. Examples of the application of this method to define a priori infill specifications and to assess the quality impact of coverage holes during acquisition are demonstrated with real data applications. (570 KB) Read more

TL #36: Source Monitoring

It is well established that modern airguns are inherently stable in a laboratory situation. However, when deployed at sea, the wavefield of arrays of airguns varies from shot-toshot because of gun drop-outs, and variations of geometry, depth, pressure, timing, water velocity, sea temperature, and sea surface conditions affecting the source ghost. (574KB) Read more

TL #35: FSB MegaSurvey

Continuing the trend towards providing MegaSurvey data volumes over the worlds most promising and active petroleum provinces, PGS Reservoir has recently announced the availability of its interpretation package on the entire 3D seismic dataset in the Faroe-Shetland Basin (FSB) on the United Kingdom Continental Shelf (UKCS) (1.8 MB) Read more

TL #34: Optical Seismic

Fiber optic seismic sensor systems have been under development for many years at PGS, who have produced several generations of prototype seismic equipment to demonstrate the technology. Ongoing projects include applications to 4C seafloor systems, streamers and near-field airgun recording. (599 KB) Read more

TL #33: 3D SRME

PGS has invested significant resources in the development of its 3-D SRME capabilities. This has led to a portfolio of methods that allows for choosing the most suitable method for each individual multiple problem at hand. (1 MB) Read more

TL #32: Flemming 4D

4D (time-lapse) seismic has become a powerful technology for oil companies to manage their reservoirs and optimize production. (519 KB) Read more

TL #31: gAS/Viper

The gAS (generic Acquisition System) and Viper systems were developed in PGS for onboard data recording, quality control (QC) and data reformat, and are the standard on all PGS seismic vessels. (1 MB) Read more

TL #30: Continuous Long Offset (CLO) Acquisition

Continuous Long Offset (CLO) acquisition is a patented, multi-vessel technique that can deliver the longer offsets and longer record lengths required to successfully image survey objectives without compromising on fold and shot sampling. (671 KB) Read more