--> ABSTRACT: Development of Crestal Collapse Structures above Dissolving Salt Anticlines: Application to Seismic Interpretation within Salt-Controlled Basins, by Randles, Tom; Clarke, Stuart M.; Richards, Phil; #90142 (2012)

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Development of Crestal Collapse Structures above Dissolving Salt Anticlines: Application to Seismic Interpretation within Salt-Controlled Basins

Randles, Tom *1; Clarke, Stuart M.1; Richards, Phil 2
(1) Research Institute for the Environment, Physical Sciences and Applied Mathematics (EPSAM), Keele University, Keele, United Kingdom.
(2) British Geological Survey, Edinburgh, United Kingdom.

Salt-controlled basins represent some of the principal hydrocarbon provinces of the world. Their potential, and their exploitation, are governed by complex three-dimensional interactions between host sediments and structural geometries related to salt mobility. However, the limitations of seismic reflection data, particularly with respect to resolution, are such that much of the complexity of salt-controlled regimes is often overlooked. In the UK Central North Sea, structures related to the Tertiary dissolution, and subsequent crestal collapse, of salt walls provide ideal geometries for hydrocarbon entrapment, but are poorly imaged on seismic data. An in-depth understanding of the structural styles that control salt wall collapse, particularly at the ‘sub-seismic’ scale, is essential in order that meaningful interpretations of potential prospects can be made based on seismic data.

The excellent exposure and preservation of a number of collapsed salt walls and related structures within the Paradox Basin, south-east Utah, USA, provides an ideal opportunity to investigate the structural development of crestal collapse structures at field scale. Detailed structural mapping and satellite image interpretation provide input to a series of idealised three-dimensional numerical models that represent the key structural styles that facilitate crestal collapse of the salt wall. These summary models are used to improve upon previous interpretations of seismic data across equivalent structures from the UK Central North Sea.

Crestal collapse of salt walls in the northern Paradox Basin is shown to be controlled primarily through development of a single listric fault, with an associated hanging-wall rollover anticline. Hanging-wall faults systems are highly complex, comprising numerous syn- and antithetic normal faults with an en-echelon arrangement, showing displacements typically in the range of 10—50 metres. Faults commonly show rapid changes in displacement along strike, resulting in complex accommodation zone geometries and numerous small closed structures. An improved interpretation of seismic data across collapsed salt walls from the UK Central North Sea is presented based on these summary models.

This work represents the early stages of development of one of the first detailed frameworks to guide interpretation of seismic data in salt-controlled basins, and has application to both exploration and production in sub-surface salt-controlled hydrocarbon provinces.

 

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