| Title | Updated geological structure and 3D intrusion model as veritable fracture driver of fracture characterization in Wayang Windu geothermal field, Indonesia |
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| Authors | M. Purnomo, W. Diningrat, N. Kamel, A. Talita, W. Dimwani |
| Year | 2023 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Wayang Windu, Fracture Driver, Fracture Characterization, Geological Structure, 3D Intrusion Model |
| Abstract | Wayang Windu is a two-phase geothermal field located in Indonesia with electricity generating capacity of 230 MW. Several make-up well drilling campaigns have been conducted since the field started commercial operation in 1999, with the most recent campaign resulting in a steam gain that significantly exceeded expectations. As part of a continuous improvement process for selecting subsurface well targets, Star Energy Geothermal is applying a novel workflow to interpret permeability distributions, especially in relatively undrilled parts of the reservoir. Theworkflow is referred to as Fracture Characterization and Optimized Well Placement (FCOWP). FCOWP consists of two main processes. The first generates fracture orientations and intensity distributions, then the second models the range of fracture apertures and lengths and includes sensitivity and uncertainty analysis. This paper focuses on the creation of Discrete Fracture Network (DFN) realizations for Wayang Windu which is part of the first process. The major initiatives related to creation of a DFN include an updated interpretation of geological structures and a model of rock intrusions. The Wayang Windu’s FCOWP methodology depends on two fracture drivers. The first fracture driver is related to faults and associated stress, and the second fracture driver is related to intrusion geomechanics and thermal cooling. The input of the fracture drivers in Wayang Windu came from recently updated geological structures and a 3D intrusion model. Each fracture driver was validated by comparing fracture properties generated by the model (dip angle and dip azimuth) with fracture data observed in wells. Fractures from the well data are explained by a certain fracture driver if a fracture with the same properties is developed by that driver in the model. This validation process shows that up to 91% of fractures at Wayang Windu are explained by fracture drivers while the other 9% are not explained and can be dealt with stochastically. Incorporating all fracture drivers results in a DFN where the fracture properties are comparable to fracture data from the wells. Thus, the updated structural model and 3D intrusion model are considered as reliable fracture drivers to predict permeability distributions in Wayang Windu to improve the selection of subsurface targets and well placement. |