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AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain

Cost-Effective, High Density, Wide Azimuth Seismic Sampling

Turki M. Al-Ghamdi1; Peter I. Pecholcs1; James A. Musser1

(1) Saudi Aramco, Dhahran, Saudi Arabia.

With most of the giant oil and gas four-way closure reservoirs discovered on land, we are now challenged with generating low-relief stratigraphic prospects from sparsely sampled spatial grids. To reduce risk, we propose a cost-efficient sampling scheme, which provides a full range of source and receiver offsets over a full range of azimuths within a square patch. This increase in source and receiver density is achieved by reducing the number of geophones per station, increasing the number of Vibroseis fleets, and using a combination of Slip-Sweep, Independent Simultaneous Source (ISS), and Distance Separated Simultaneous Source (DS3) recording techniques to maintain high production levels and high trace density for improved seismic data quality at reservoir objectives.

Recent field tests have shown that a reduction in the number of sensors per receiver group combined with an increase in source/receiver sampling density has a minimal impact on seismic data quality. Such trade-offs shift the main focus of random and coherent noise attenuation from the field arrays to the processing center. With the increase in recording channels and the reduction in the number of geophones in the field (or the use of single digital sensors per station), the overall cost of a seismic crew is minimally impacted.

To achieve the optimum wide azimuth square patch design, Vibroseis source points (VPs) can be positioned outside a dense receiver line patch. Although the source stations in such a design are typically reoccupied, the overall source productivity can be doubled (or better) by using two or more simultaneous Vibroseis sources separated by the width of the patch. This distance separation will also reduce interfering cross-talk and harmonic noise interference from the other Vibroseis sources. Equivalent sensor roll-rates can be easily achieved by reducing the source line interval (and increasing the resulting source density for better sampling). This balance between source and receiver effort provides a superior spatial sampling grid with minimal impact on existing seismic crew configurations.

We show how this new seismic crew configuration and design provides superior reservoir characterization with only an incremental increase in survey cost.