Fracture Attribute and Topology Characteristics of a Geothermal Reservoir: Southern Negros, Philippines

Pastoriza-Primaleon, Loraine; McCaffrey, Kenneth J.W.; Holdsworth, Robert E.

Abstract

The characterization of fracture networks using attribute and topological analyses has not been widely applied to the understanding and prediction of the secondary porosity, permeability and fluid flow characteristics of geothermal resources. We acquired fracture length, aperture, intensity and topological data from remotely sensed images and surface exposures of the Cuernos de Negros region and compared these data with well cores and thin sections from the underlying active geothermal reservoir: the Southern Negros Geothermal Field, west central Philippines. We show that the fracture attributes of the analogue and reservoir are best described by a power law distribution of fracture length and aperture intensity across six to eight orders of magnitude. This characterization of outcrop and borehole fractures validates the use of surface exposures as analogues for the Southern Negros Geothermal Field reservoir rocks at depth. An observed change in the scaling exponent in the 100–500 m length scale suggests that regional to sub-regional fracture systems scale differently from those at the meso- and macroscale, which may be a strata-bound effect or a sampling issue. Topological analyses show a dominance of Y-nodes and doubly connected branches, that indicates a high degree of fracture connectivity, which is important for effective fluid flow.

Citation

Pastoriza-Primaleon, L., McCaffrey, K. J., & Holdsworth, R. E. (2020). Fracture Attribute and Topology Characteristics of a Geothermal Reservoir: Southern Negros, Philippines. Journal of the Geological Society, 177(5), 1092-1106. https://doi.org/10.1144/jgs2019-126

• Journal Article Type: Article
• Acceptance Date: Apr 30, 2020
• Online Publication Date: Jun 5, 2020
• Publication Date: 2020-09
• Deposit Date: May 7, 2020
• Publicly Available Date: Jun 5, 2021
• Journal: Journal of the Geological Society
• Print ISSN: 0016-7649
• Electronic ISSN: 2041-479X
• Publisher: The Geological Society
• Peer Reviewed: Peer Reviewed
• Volume: 177
• Issue: 5
• Pages: 1092-1106
• DOI: https://doi.org/10.1144/jgs2019-126
• Public URL: https://durham-repository.worktribe.com/output/1264762