From Bureau of Economic Geology, The University of Texas at Austin (www.beg.utexas.edu).
For more information, please contact the author.

AAPG Southwest Section Seminar, Abilene, Texas, November 23, 2002

Paleocave Reservoirs: Origins, Burial-Depth Modifications, Spatial Complexity, and Reservoir Implications

Robert Loucks

ABSTRACT:

Paleocave systems form an important class of carbonate reservoirs that are products of near-surface karst processes and later burial compaction and diagenesis. Origins of fractures, breccias, and sediment fills and other features associated with paleocave reservoirs have been studied in modern and ancient cave systems. Information about such cave systems can be used to reconstruct the general evolution of paleocave reservoirs and understand their associated scale, pore networks, and spatial complexities at various depths of burial.

The 7-hour seminar covered the following topics:

· Introduction to Karst Systems
· Modern Cave Origin and Development
· Evolution of Cave Passages from the Surface to Deep Subsurface
· Paleocave Facies Classification
· Evolution of Cave Systems from Surface to Deep Subsurface
· Core Logging Exercise
· Coalesced Collapsed Paleocave System Mapping Exercise
· 3-D Architecture and Features of a Coalesced Collapsed Paleocave System
· Some Other Origins of Caves (Vugs, Breccias, Fractures)
· Seismic Examples of Coalesced Collapsed Paleocave Systems
· Examples of Paleocave Reservoirs
· Comments on Development of Paleocave System Reservoirs
· Comments on Exploration for Paleocave System Reservoirs
· Discussion

The goal of the seminar is to provide the participant with the ability to:

· Understand the origin of paleocave reservoirs and their dimensions.
· Appreciate the internal architecture and spatial complexity of collapsed paleocave reservoirs.
· Recognize paleocave reservoir systems from cores, image logs, wireline logs, and seismic.
· Predict dominant paleocave pore network relative to depth of burial.
· Apply concepts of reservoir characterization to this complex carbonate system.