ダリール油田における地震探査の適用

Abstract

The Daleel oil field is located at the western corner of the Wadi Aswad contractarea of Japex Oman Ltd. Basic seismic exploration of 2, 883km in line length in this area wascarried out during 1981-1983. Several additional seismic surveys including two 3D surveys wereperformed later in the Daleel oil field and adjacent area for the purpose of reservoir delineation. Specifications of the former field data acquisition were basically 120 channel and 60 fold. Westarted first with end-on spread at 30m receiver and source intervals, and a few months laterchanged it to split spread at 50m receiver and source intervals. The latter specifications weresimilar to so-called ‘(ideal) stack array’ which was discussed later a lot on The Leading Edge ofGeophysics in 1986. This change seems to have contributed to speeding up work progress and toacquiring data in requisition of broad band, no much skew, and wide dynamic range, with leastnoise for tracing subtle and cache information. The stack array was generally good as spacedomain filter design and needed no much additional, irrationally large labor efforts.Uphole shooting from the depth of 40m on average at 465 points was useful not only forcalibrating weathering correction data, but also studying shallow layer situations, which did notalways fit typical two layer model.Interpretation pitfalls were checked occasionally on cross points of lines when trackingstratigraphical or lithological features in 2D seismic sections.After checking surface seismic velocity data with those of nearby wells we found veryreasonable harmony between them and successfully estimated a standard velocity function.Our main concern was to delineate reservoir features of the Daleel area. The effort delineatingthem also resulted in better definition of fault systems and subtle structural features. Everyinformation used here contributed to integrating complete interpretation.