Abstract
Understanding fracture development in the context of the chemical and physical processes undergone by the reservoir from deposition through burial is a powerful tool for reservoir characterization. These processes control the distribution and density of different fracture types and their effective flow properties. Classification of fractures from a genetic standpoint has provided a robust framework to develop conceptual models on fracture distribution in this large carbonate field.
Three distinctive fracture generations are defined in this field based on direct core observations. Generations are named A, B, C based on their relative timing. Generation A corresponds to syn-depositional fractures, often filled with volcanic debris and early marine cements. Generation B corresponds to burial related fractures that develop due to vertical loading and compaction. They often appear in association with stylolites. Generation C also forms in the burial realm and they are thought to be related to overpressure in the context of the hydrocarbon charge.
Integration of core and image log observations suggests that syndepositional fractures are more abundant along the rim, with the maximum occurrence at the outer platform to slope transition. Burial fractures, on the other hand, are ubiquitous across the field. High fracture densities occur in the slope where dissolution processes also enhance the fracture network. The dynamic potential of these features is supported by the presence of severe mud losses while drilling, which is used as a proxy for excess permeability in the absence of well test or production data. Lost circulation events are evaluated using observations from core and image logs to determine their root cause.
