Penetrating Evaporites--New Information from Old Seismic Data in Suez Rift, Egypt

Stephen K. Perry, Susan L. Gawarecki, Steven Schamel

Structures in the prerift sediments, Gulf of Suez, are of primary interest for petroleum exploration. However, the overlying thick blanket of Miocene synrift evaporites severely limits resolution of deep structures in seismic reflection lines. A technique for maximizing accuracy of prerift maps and sections is illustrated by examples from the south-central Gulf of Suez. Preliminary structural maps of prerift units are generated from limited well data, good seismically derived maps of the base evaporite, and fragmentary deep seismic data. Through rigorous application of conventional cross section balancing techniques and geometric "rules" for listric normal fault-block rotation, trial cross sections are constructed. Construction of trial cross sections relies heavily on th following information from seismic lines: (1) thickness variations of synrift fill; (2) sequence boundaries representing unconformities over buried tilt blocks; (3) dip domains faintly visible beneath Miocene evaporites; and (4) faulting in Miocene sediments in response to deeper normal faults.

The integration of well data allows control of seismic interpretation and of depth to prerift rocks. The sections are refined through iteration and are then used in conjunction with areal balancing methods to correct the structure maps. The subsequent serialization of balanced sections results in an internally consistent, geometrically constrained, three-dimensional picture of the basin which best fits all the available data. Important information on prerift structures which results from this technique includes location of normal faults and the magnitude of their throw, attitude of deep tilt blocks, and location of tilt-block terminations. Using this methodology, old prospects can be refined and new plays and prospects generated. These can then be tested by local detailed seismic work or by the drill.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.