--> Abstract: The Effects of the Properties Changes of the Near-surface on Seismic Repeatibility at Naylor Field, by Yousuf Y. Al-Jabri and Milovan Urosevic; #90105 (2010)
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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

The Effects of the Properties Changes of the Previous HitNearNext Hit-Previous HitsurfaceNext Hit on Seismic Repeatibility at Naylor Field

Yousuf Y. Al-Jabri1; Milovan Urosevic1

(1) Exploration Previous HitGeophysicsNext Hit Department, Curtin University of Technology, Kensington, WA, Australia.

High seismic repeatability is critical to the monitoring program of the Naylor Field because of small time-lapse effect related to CO2 injection into depleted gas reservoir (Naylor). To understand the effect of ground conditions and improve repeatability we conducted so-called “micro-array” investigations of the Previous HitnearNext Hit-Previous HitsurfaceNext Hit layers at this site.

A feature of the injection test site area is the Previous HitnearNext Hit-Previous HitsurfaceNext Hit karst topography. In such geological terrane, any change in water table level can influence the seismic response due to change in a scattering pattern. Hence the aim of micro-array measurements is to determine the properties of the Previous HitnearNext Hit Previous HitsurfaceNext Hit layers during the wet and dry seasons. This could help us understand and ultimately predict the seismic response and hence survey repeatability. The elastic properties measured are then used for the forward modeling of the seismic response to variable soil conditions. Comparison of numerical and field data will allow us verify the validity of this approach.

More specifically we investigate the variation of elastic properties of both top soil and the deeper rugose clay-limestone interface as function of water depth level. Such tests in fact simulate the measurements conducted in dry and wet seasons and evaluate the effect of these seasonal variations to seismic signature, which is then analyzed in terms of non-repeatability. In this study we use both micro-borehole (micro VSP) and micro-refraction arrays to analyze directional properties on the Previous HitnearNext Hit-Previous HitsurfaceTop. These measurements are subsequently calibrated by core sample tests. Finally numerical tests are performed with calibrated soil.