Surface Seismic Multicomponent Imaging of Deep Tight Gas Sands

Ron Harris¹ and John O'Brien^2
1Bossier Development, Anadarko Petroleum, The Woodlands, TX
²Geophysical Technology, Anadarko Petroleum, The Woodlands, TX

In 2004, Anadarko Petroleum initiated a comprehensive geophysical program to evaluate how to best image deep over-pressured tight gas sands in the East Texas Basin, USA. These Upper Jurassic sands have a low acoustic impedance contrast with the encasing shales leading to a weak P-P reflectivity series. This program included the following elements:

1) 3-D Seismic Imaging. A 72 sq. mile conventional 3-D seismic survey was recorded with single-component analog geophones. The seismic source consisted of buried explosive charges infilled as needed with vibroseis source points.

2) Multicomponent Seismic Imaging. A 9 sq. mile three-component 3-D survey was recorded with a static spread of Vectorseis accelerometers centrally embedded within the larger conventional 3-D survey. All source points for the conventional P-wave survey were recorded concurrently by the Vectorseis spread.

3) Multi-offset, multicomponent VSP survey. The objectives of the VSP program were (a) to provide direct observation and comparison of P-P versus P-S imaging of these tight gas sands, (b) to provide calibration of the P-P and P-S surface seismic data to well log data, and (c) to provide a means of registering the P-P and P-S data.

The VSP program, provided strong encouragement for the use of 3-D surface multicomponent seismic to image deep tight gas sands. The P-P 3-D survey was also successful, producing significantly improved imaging of the target interval when compared to existing 2-D data. However, the P-S imaging of these deep targets (12,000’ - 16,000’) was disappointing. The deep section experienced poor signal to noise, limited bandwidth, and image quality that was inadequate for structural mapping purposes.

In this poster we present the P-P and P-S 3-D seismic results, and discuss possible factors that may have influenced the surface seismic multicomponent imaging results.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas