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Results: 126

Broadband seismic technology and beyond: Part VIII BroadSeis in explorationBroadband seismic technology and beyond: Part VIII BroadSeis in exploration
Geo Expro, March, 2014
Vetle Vinje | Jo Firth
Summary
The advantages of broadband seismic have been demonstrated around the world at all stages in the exploration and production cycle, for many different geologies, and in various different environments. High frequencies produce sharp wavelets, while low frequencies reduce sidelobes, so that with broadband, seismic events are single peaks or troughs corresponding to genuine geological layers. This clarifies impedance contrasts and creates sharp images of small features as well as clear differentiation between different sedimentary packages
Model-based Water-layer DemultipleModel-based Water-layer Demultiple
First Break, March, 2014
Ping Wang | HongZheng Jin | Min Yang | Yan Huang | Sheng Xu
Summary
This paper focuses on the attenuation of Water-Layer-Related Multiples (WLRMs) which reflect at least one time between the water bottom and the water-air surface. WLRMs are often the most dominant multiples in shallow-water seismic data. We propose a Model-based Water-layer Demultiple (MWD) algorithm to calculate the Green?s functions of the Water-Layer Primary Reflections (WLPRs) based on a known water-layer velocity model and then convolve them with the recorded data to predict the WLRMs. Combined with adaptive subtraction, MWD can effectively attenuate WLRMs. We apply MWD to field data from the Hibernia oil field area which has a water depth of approximately 70-90 meters. The results show that while SRME by itself has limited success, MWD is effective in attacking water-layer-related multiples. The effectiveness is attributed to the fact that MWD predicts the multiple models with correct relative amplitude and a spectrum similar to the input data?s. SRME, on the other hand, suffers in shallow-water situations, primarily due to cross-talk among multiples. Once the WLRMs are removed by MWD, successive SRME can then be applied to predict and eliminate other types of surface-related multiples (SRMs) which tend to have longer periodicity and less cross-talk. The combination of MWD and SRME is demonstrated as an effective multiple attenuation package for shallow-water data and results in fewer residual multiples and better preserved primaries over tau-p gapped deconvolution. This, in turn, contributes to a more realistic velocity model and, finally, higher quality images.
Integrating surface seismic, microseismic, rock properties and mineralogy in the Haynesville shale playIntegrating surface seismic, microseismic, rock properties and mineralogy in the Haynesville shale play
First Break, February, 2014
Gabino Castillo | Simon Voisey | Kevin Chesser | Norbert Van De Coevering | Antoine Bouziat | Guy Oliver | Chi Vinh Ly
Summary
Workflow integrating reservoir and geomechanical properties obtained from pre-stack seismic inversion and incorporating stress and fracture information extracted from azimuthal analysis of the seismic data.
An efficient 4D processing flow for variable depth streamer dataAn efficient 4D processing flow for variable depth streamer data
Leading Edge, February, 2014
Eric Hicks | Henning Hoeber | Gordon Poole
Summary
We present a new processing algorithm to co-datum two or more streamer datasets acquired with different cable shapes to a common depth. This method is applied early in the processing sequence so that standard 4D co-processing can easily be performed. The core of this technique, Ghost Wavefield Elimination (GWE), can also be used to remove as much of the ghost in the legacy data as possible. A North Sea data example from early 2013 is used to demonstrate these ideas. We achieve excellent 4D repeatability with around 10% background noise (NRMS).
Ekofisk Life of Field Seismic: Operations and 4D ProcessingEkofisk Life of Field Seismic: Operations and 4D Processing
Leading Edge, February, 2014
Sebastien Buizard | Henning Hoeber | Nam Pham | Sylvain De Pierrepont | Jon Schultzen
Summary
In 2010 the world?s currently largest optical Permanent Reservoir Monitoring (PRM) system was installed in the southern part of the Norwegian North Sea at Ekofisk. The Life of Field Seismic (LoFS) system consists of 3966 seabed multicomponent sensors along 200 km of mostly trenched fibre optic seismic cables and covering about 60 kmĀ² of the Ekofisk field. Seismic data are acquired via a top side recording unit (Nakstad et al., 2011) and a containerized source operated on a supply vessel. Five vintages of data were acquired between the end of 2010 and spring 2013 and a sixth one is scheduled to complete in fall 2013. In this paper, we present the different aspects of seismic operations at Ekofisk: seismic source, recording system and data transfer, QC and processing. One of the key factors in achieving the full value of a PRM system is to be able to handle such operations in a safe, integrated and efficient manner in order to deliver high quality seismic volumes for interpretation with rapid turnaround. We discuss in more detail key aspects of the 4D processing sequence, designed for robustness and optimal turnaround. Throughout, we show how integration of the different operational phases of the LoFS project, as well as integration of expertise between client and contractor, plays a key role in delivering clean, well resolvable 4D signals and low residual 4D noise with NRMS down to 5%. The high quality data delivered by operations and processing is now routinely used in well planning and reservoir management workflows.
Innovations for geophysical monitoring of 3D and 4D marine surveysInnovations for geophysical monitoring of 3D and 4D marine surveys
First Break, November, 2013
Julie Svay | Yuan Ni | Cheikh Niang | Nicolas Bousquie | Anna Sedova | Thomas Mensch
Summary
Time-lapse seismic surveys are carried out to reveal production changes in the subsurface reservoir. Ensuring optimal repeatability between the different vintage surveys provides a direct way to minimize 4D noise unrelated to reservoir changes. Positioning repeatability is one of the main issues in 4D towed-streamer acquisition. It is primarily optimized by steering the vessel, source and streamers to match the previous acquisition (or baselines). The remaining mismatches in positions must be assessed to ensure the high quality of the data being acquired. We address the 4D repeatability of positioning through a geophysical target-oriented approach, where repeatability is assessed from the impact on seismic illumination. New and complementary repeatability indicators are derived for onboard quality control at gradual discrimination scales, ranging from shots through navigation lines up to the full acquisition.
Can land broadband seismic be as good as marine broadband?Can land broadband seismic be as good as marine broadband?
Leading Edge, November, 2013
Michel Denis | Valerie Brem | Fabienne Pradalie | Frederic Moinet | Matthieu Retailleau | Jeremy Langlois | Bing Bai | Roger Taylor
Summary
The recent development of techniques to extend the bandwidth of marine towed streamer surveys has significantly changed the marine seismic landscape. In fact it has coined the new category of ?Broadband Seismic? now synonymous with the marine towed streamer market. The bandwidth challenge for marine towed streamer seismic is well-documented and is related to mitigating, or completely removing, the interference pattern from the interaction of the upgoing primary wave and its surface reflection (i.e. its ghost) at the source and receiver side. The interference results in the ghost notches in the amplitude spectrum which bound the useful bandwidth of the data at the high and low ends of the spectrum.
Salt emplacement-induced azimuthal anisotropy in Garden Banks, Gulf of MexicoSalt emplacement-induced azimuthal anisotropy in Garden Banks, Gulf of Mexico
Geophysical Society of Houston, October, 2013
Hao Shen | Guang Chen | Tianjiang Li
Summary
Azimuthal anisotropy often exists near salt diapirs, where we may observe radial faulting caused by salt emplacement. Seismic imaging with wide-azimuth or multi-azimuth datasets enlightens us to the existence of azimuthal anisotropy. However, if the azimuthal anisotropy is then neglected during velocity model building, inconsistent residual moveouts among azimuths may remain in the common image gathers (CIGs) around these areas. This can prevent a clear definition of the radial faults and other dipping events in the stacked image. Here we provide a geological explanation to for the azimuthal anisotropy near steeply dipping salt flanks in the Garden Banks region of the Gulf of Mexico (GOM). We present a production workflow to describe the discrepancy of wave propagation speed with different azimuthal angles using a tilted orthorhombic (T-ORT) anisotropy model. We demonstrate image improvements near dipping salt flanks when we correctly account for the azimuthal anisotropy.
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