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Magnetically Inferred Basement Structures in the Central Part of the Kuwait Arch
(1) Exploration, Kuwait Oil Company, Ahmadi, Kuwait.
Magnetic
data over the Kuwait Arch concealed by overlying Phanerozoic strata, shows a broad circular magnetic high over the Kuwait Bay area and a conspicuous E-W trending associated magnetic low on the north over the Bahrah area of nearly comparable amplitude. The gravity and seismic data shows a major high over the same area which is as per the tectonic events in the area. The present study is focused on the conspicuous magnetic low over the crestal part of the dominantly N-S trending Kuwait Arch where a comparatively complex Bahrah oil field is located. On the basis of magnetic signatures, it appears that shield elements (basic metavolcanics like basalt and rhyolite with high magnetic susceptibility) extend beneath Phanerozoic cover resulting in a dipole signature of magnetic anomaly. In order to infer the basement structures lying beneath the Bahrah and Kuwait Bay areas, magnetic anomaly data has been processed, filtered and integrated with the gravity and seismic data.
To locate the observed magnetic anomalies directly over the magnetic source bodies that caused these anomalies, the Total Magnetic Intensity (TMI) data has been transformed into Reduced-To-Pole (RTP) map. The TMI data also processed for 3D Analytic Signal, produces maxima over magnetic contacts regardless of the direction of magnetization. The enhancement of magnetic anomalies associated with faults and other structural discontinuities was achieved by the application of bandpass filter (4-12km) to the TMI-RTP data which defined the best continuity and resolution of the linear features.
Basement structures, faults and shear zones can easily be traced along linear features which prove the effectiveness in the interpretation. Faults and shear zones coincide with zones of significant changes in magnetic and structural characteristics. The NNE-SSW orientation of basement-involved structures over Bahrah and Kuwait Bay area are easily identified on bandpass filtered TMI-RTP data. The Bahrah oil & gas wells producing from Cretaceous/Jurassic levels are located on magnetically inferred basement highs. Basement structural highs control the structural development of the sedimentary cover. The magnetic
data after integration with gravity, seismic, borehole and geologic data reveals the elements of basement structures over which the Bahrah oil field is located. This study can assist in effective placement of future wells in Kuwait Bay and Bahrah area.