Re-Interpretation of the North Flank of Qarun "A" Field (Western Desert, Egypt), Based on SCAT Analysis and Reprocessing of the A-17 Dipmeter

James D. Morse
Computational Geology, Inc, Weybridge, VT

The A-17 penetrates the steep northwest flank of Qarun “A” Field, an asymmetric, SW—NE anticline in Egypt's Western Desert. The original dipmeter processing indicates <10° dip to the WNW from ~7850' (MD) to ~8565', where dips increase abruptly to ~35°. Based on this, interpreters inferred that at the A-17 the NW limb dips ~35°. We re-analyzed the A-17 using Tangent Plots, SCAT, etc. Below 8565', the data were highly scattered on Transverse and Longitudinal Plots, but stopped abruptly at an apparent dip of 35°. This clipping is even more obvious on Dip vs. Azimuth and Tangent Plots, which show that dips and azimuths are highly scattered, with no dips >35°. We suspected that below 8565' (1) the search angle (35°) had been set too low, (2) most if not all of these computed dips were noise, and (3) the actual dip below 8565' is much higher than 35°. We re-processed the dipmeter using a search angle of 80°. The results show that dip increases rapidly from < 10° above 8585' to 60° at ~8625', thus confirming our suspicion.
Although much modern dip data have been picked by hand and do not involve search-angle problems, there are thousands of logs that have been picked by machine. Some, like the A-17, may have been processed with incorrect search angles. A careful check of machine-picked logs for this problem could (1) prevent the drilling of unnecessary dry holes or (2) lead to new discoveries or improved reservoir management.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece