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Mitigating Water Encroachment in a Fractured and Faulted Carbonate Gas Field: An Uncertainty Management and Field Optimization Study Using Unstructured Discrete Fracture Models

Robin Hui
Chevron Energy Technology Co., San Ramon, California, USA

The reservoir of interest is early Triassic bedded dolostone and limestone, located at a depth of more than 3 km. The depositional environment is carbonate platform and ramp with oolitic shoals. Gas is trapped in different pools in thrust-related anticlinal structures and seals comprise tight limestones and anhydrites. There is well-based data suggesting the existence of effective natural fractures: well productivity indicates substantially higher permeability than expected from matrix, and natural fractures are commonly seen in core and image logs. Several major faults also exist in the reservoir and are thought to be sealing. Because high-permeability fractures have been known to result in significant downside risks to gas production (rapid water breakthrough), it is important to assess their impact on fluid flow for effective development planning. In this work, we will describe a study to evaluate the effects of natural fractures on gas and water production for this field. The focus was to address the chief field-development-plan concerns around aquifer-water mitigation and well-pattern optimization. An experimental design (ED) approach that entails multiple unstructured discrete fracture models (DFMs) for a large sector of the field was applied.

AAPG Search and Discovery Article #120034©2012 AAPG Hedberg Conference Fundamental Controls on Flow in Carbonates, Saint-Cyr Sur Mer, Provence, France, July 8-13, 2012