Application of Advanced Seismic Attributes for Fault Network Characterization in Geothermal Exploration
[HIE Geo-energy consultancy, Netherlands]
The prospects of geothermal exploitation in the Netherlands (NL) are on an upward trend following resolutions by the Dutch government to gradually phase out dependence on energy from the Groningen gas field. The Master Plan for Geothermal Energy in the NL lays foundations to increase geothermal production from the current 830000 Megawatt Hour (MWh) to a planned 55555555 MWh by 2050. Estimates of the technical potential in the NL is around 277777777 MWh. This “New Energy” is expected to be tapped by greenhouse horticultural and district heating. The seven strata in the NL that are potentially suitable for geothermal exploitation are the Rotliegend, the Triassic, the Jurassic-Chalk, the Upper Carboniferous, the Chalk, the Tertiary and Zechstein plays. The ultra-deep geothermal energy (UDG) potential is most promising in the three Dinantian sub-plays, namely, Friesland, Midden-Nederland and Rijnmond. Around 80 % of the demand for heat in the NL is in areas where there is little subsurface knowledge. Hence de-risking geology during the exploration phase of geothermal plays is crucial. The Dutch government has set a positive example by mandating the release of 3D seismic datasets to the public domain within a stipulated time by operators. Synergies between the oil and gas industry and the geothermal sector is encouraged with respect to industry best practices in subsurface modelling. In this contribution, we highlight the utility of efficient workflows for fault mapping based on 3D seismic data for geothermal developments. Geothermal systems are dominantly fracture-controlled i.e. structural settings and resultant fault architecture can dominate flow and thermal response of fluids and hence determine the ultimate productivity of a planned development. Fault step over regions, fault intersections and fault tips are often favorable targets for geothermal drilling. On the other hand, faults may also act as flow barriers due to sealed and non-conducting fault cores, fault-controlled hydrothermal developments, therefore, require a systematic structural analysis to understand natural permeability patterns. Conventional fault characterization workflows based on reflection seismic involve a great deal of manual effort in tracing faults. We present an automated workflow to characterize fault planes from 3D reflection seismic. The methodology involves a novel workflow of advanced seismic attributes i.e. dip steered and filters followed by harmonic signal processing-based edge detection and finally automated fault plane rendering. Our technique is able to extract fault planes and calculate fault intersection and terminations delivering and revealing rapid 3D fault network patterns in an automated manner with. We are able to create rapid fault geometry realizations that can subsequently be used as an input for numerical simulations of fluid, heat transport, or coupled processes such as pore pressure changes related or due to induced seismicity along faults. We showcase our methodology to a case study from a seismic dataset from the F10 Block, Dutch offshore. The example that is presented encompasses complex faulting over the characteristic group dominated by carbonates. The methodology enables to determine a robust fracture characterization that may be applied to any 3D reflection seismic dataset.
|        Topic: Exploration||Paper Number: 11162|