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Articles
Autonomous Nodes For Time Lapse Reservoir Seismic: An Alternative To Permanent Seabed Arrays
Time lapse (or 4D) seismic monitoring of producing oil fields is an accepted method for optimisation of field development and product recovery, providing significant improvements in recovery rates and savings in drilling costs. This paper provides an overview of the concept and design of an autonomous seismic node recording system, and a comparative analysis of using nodes versus permanent sensor cable installations for 4D seismic analysis and monitoring of an oil field.
PN101_SeaBird.pdf
Node Seismic Study Continues to Gain Momentum
Two major milestones both in the US Gulf of Mexico have recently been passed in the emerging ocean bottom node (OBN) geophysical technology. First, SeaBird Exploration has conducted the industry´s first ever multi client 4C OBN survey in Southeast Green Canyon Area in water depths ranging from 1,300 to 2,200 metre water depths. This multi client approach was done to enable potential user of this technology to have low cost access to actual raw field data – a valuable resource for use in planning and execution of future node programmes.
Node Seismic Study Continues to Gain Momentum.pdf
Emerging Geophysical Technologies: Is Planting and Re-planting of Nodes in a 4C-4D Scenario the Optimum and Most Cost-Effective Solution for Field Reservoir Monitoring?
Seabed data acquisition methods offer numerous advantages over towed streamer data. These advantages can lead to improved static and dynamic reservoir characterization. By recording complete vector field data at the sea floor with full azimuth acquisition improved shallow resolution, signal-to-noise ratio, spectral content, deep imaging and 3D illumination can be achieved. Also in the presence of obstacles such as production facilities a regular coverage can be assured.
Improved Sihil Image From 4C Full Azimuth Node Data
AA large 4C OBS seismic program was acquired for Pemex over the Cantarell field offshore Mexico to improve the structural definition of the deeper Sihil field underlying the giant Akal field. The acquisition was made using autonomous receivers planted with accurate positioning on a regular grid in the seabed. The data is acquired with a regular and full azimuth/offset distribution. High quality data was recorded. The PP and PS data is time processed with migration before stack. Better resolution of the top of the Sihil under the overthrust of Akal is obtained. The converted wave has a better resolution for the shallower data.
Evaluation and impact of sparse-grid, wide-azimuth 4C-3D node data from the North Sea
In July 2002 a 3D multi-component survey was recorded on a North Sea field as part of the DEMO 2000 sponsored IMPREDO project. The recording systems deployed were autonomous nodes: the result of over 5 years of research, development and testing of 4C systems. The PP dataset has been successfully processed with full 3D pre-stack time migration.
Vector Fidelity Analyses of Seabed Seismic Data
The vector fidelity analyses are performed on the first break of three different data sets. RMS mapping, modelling, polarization analyses and frequency analyses all prove to differentiate the sensors with respect to vector fidelity. One cable sensor and three planted sensors (nodes) are evaluated. There are significant differences between the cable sensor and the planted nodes. The results suggest that cable sensors are not qualified for wide azimuth acquisitions.
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