--> ABSTRACT: Structural Modeling of Overturned Beds Using Dips from Wells Near Salt Structures, Northern Gulf of Mexico, by Xu, Weixin; Lewczynski, Nicole ; Etheredge, Mark R.; #90142 (2012)

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Structural Modeling of Overturned Beds Using Dips from Wells Near Salt Structures, Northern Gulf of Mexico

Xu, Weixin *1; Lewczynski, Nicole 1; Etheredge, Mark R.2
(1) Schlumberger, Houston, TX.
(2) White Oak Energy, Houston, TX.

Many oil fields in the Gulf of Mexico (GOM) basin are affiliated with salt structures. With new technologies, more oil is being extracted from these fields. However, subsalt exploration and development presents various challenges to the oil industry, one of which is to define structures and reservoir volumes beneath salts. As more wells have been drilled around salt domes, it is observed that many beds around salt domes are overturned. The overturned beds are found in offshore subsalt fields as well as onshore fields related to shallow piercement salt domes. These overturned structures can sometimes be interpreted from regular, open-hole wireline logs, such as Gamma Ray curves and Spontaneous Potential curves. They show up symmetrically about a hinge point. Regular wireline logs, however, are usually one dimensional. Many overturned structures coexist with faults and local unconformities, and do not have symmetric log features. All these make the interpreting of overturned structures near a salt dome very difficult, if not impossible.

Dips from borehole images have been used to define reservoir structures for many years; dips from tri-axial resistivity logs have started being used only recently. However, the interpretation of the dips from these tools is not straightforward, especially when overturned folds and faults are present near salt structures. Software for structural interpretation and visualization from formation dips derived from borehole images is sometimes used to model structures. Its application in the GOM to visualize overturned structure affiliated with salt domes has helped in the interpretation of these complex structures.

This paper presents interpretation of overturned structures using structural modeling and visualization software in a few examples from the GOM. The results suggest that many oil reservoirs surrounding salt structures in Louisiana and Texas remain to be exploited for remaining reserves. Without the use of dips from openhole logs and structural modeling, it would not have been possible to identify these structures.

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California