--> Abstract: A Comprehensive Classification of Seals Based on Worldwide Subsurface Analogs; #90063 (2007)

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A Comprehensive Classification of Seals Based on Worldwide Subsurface Analogs

 

Guzmán, José I.1, Rod Sloan2, Shengyu Wu1, Shaoqing Sun2 (1) C&C Reservoirs, Inc, Houston, TX (2) C&C Reservoirs, Ltd, Maidenhead, Berks, United Kingdom

 

We have erected a comprehensive classification of seals based on the number, type, location, and combination of sealing surfaces of nearly 1000 reservoirs from around the world. Previous classifications focused on sealing and leaking mechanisms, on capillary properties, or on geometric configuration, but they have not been empirically tested or calibrated with the height of hydrocarbon columns. Our classification involves three end-members and their combination into nine families: Simple Top seals, Updip Lateral Fault seals, and Lateral Stratigraphic seals. Over one-half of the world's largest reservoirs are sealed by combination seals, and nearly half of the ultimately recoverable reserves in the reservoirs studied are contained in traps with simple top seals.

 

Our seals classification is the foundation for a systematic checklist of parameters that must be accounted for when evaluating the seal chance of success. For prospects involving only a simple top seal, key parameters include the lithology, thickness, depositional system, and orientation of the seal with respect to the trap, as well as the presence/absence of faults in the cap-rock. When updip fault seals are required, parameters such as the ratio of fault throw to reservoir thickness, maximum burial temperature, and structural dip, should be considered in addition to those listed for simple top seals. If the prospect involves lateral stratigraphic seals, the nature of the updip change in facies and the structural dip are the most important parameters. Commonplace conjectures in risking seals can be minimized by pre-drill methods that provide clues to these parameters.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California