The three-dimensional seismic interpretation of Arab-D Reservoir, Uthmaniya Area, eastern Saudi Arabia
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Saudi Digital Library
Abstract
The study utilized the 3-D seismic interpretation method to interpret Arab-D reservoir in GOSP 2&7 area in the northern part of north Uthmanyah field NE Saudi Arabia. GOSP 2&7 is bounded between inline 7932 and 7230 NS and between crossline 1781 and 712 EW. Arab-D marker and the faults cutting it are mapped in the whole survey at every 10th line. Mapping every 5th line, every 2nd, and every other line were used for the detail mapping and infill-picking. The 3-D seismic interpretation method is discussed in chapter one. The discussion summarizes the main interpretation objectives and gives more attention to the structural interpretation method, which is the main objective of this study.
The 3-D seismic interpretation provides two way travel time (TWT) and fault maps of the top Arab-D horizon in GOSP 2&7 area. The main structural elements in GOSP 2&7 area include NNE to NS anticline axis plunging toward the north, EW high angle normal and reverse faults, and NW NE secondary faults. The EW high angles normal and reverse faults group interacted to produce an association of both graben and horst at different scales. This association may be due to a compressional stress after an extensional stress related to the Oman and reactivation of Najd fault system. The model suggests the possibility of Zagros impact in the lower strata such as Arab-D horizon. The study combines seismic and time slices to enhance the 3-D interpretation. Comparison of the TWT and fault maps with the flattened coherency maps shows an excellent correlation. This result can provide a useful tool for fault extrapolation in un-interpreted areas. The Arab-D marker doubling was observed and mapped at several localities of the area. This phenomenon may be an indication of calcarenites lens or bands that are porous and permeable. Seismic section and time slices movies are excellent tool for mapping these bands. The area faults continue cutting across the upper strata up to Tertiary and lower horizons of pre-Permian. Other sets of fault operated only within the Jurassic carbonate and died out in one of the anhydrite zones. Some small-scale faults have, only, a local impact on Arab-D marker and/or next to it. The TWT maps and seismic sections show the presence of faults free zones which are assumed to be of low porosity and permeability and, probably, of low fluid movements.