Geothermal Application of Borehole Logging in New Zealand

Transcription

1 Geothermal Application of Borehole Logging in New Zealand D. McNamara, C. Massiot, M. Lawrence HADES 2011, 25th May

2 New Zealand s High Temperature Geothermal Logging Drilling Parameters e.g. rate of penetration Cuttings and core PTS (Pressure, Temperature and Spinner) Mechanical caliper Natural gamma Temperature & pressure profiles (heat-up runs) Deviation surveys Since 2009 high temperature BHTV (acoustic televiewer - AFIT) Combined these data resources have useful application to the geothermal industry in New Zealand

3 Applications Borehole Quality Mechanical caliper, acoustic televiewer Structural Analysis Acoustic televiewer, core and cuttings, drilling parameters Stratigraphic Refinement Acoustic televiewer, natural gamma, cuttings and core, drilling parameters Core Correlation Acoustic televiewer, core Permeability Identification PTS tools, acoustic televiewer, temperature and pressure profiles 3D Modelling

4 Borehole Acoustic Televiewer Run in 14 wells in 5 fields since 2009 Answers an increased interest by developers to improve understanding of fracture permeability in New Zealand high temperature geothermal fields

5 Borehole Acoustic Televiewer tool : AFIT

6 Borehole Quality 3D borehole image Borehole cross-section Acoustic amplitude Tool centralized, circular borehole Tool decentralized / cave on one side of the borehole Drill pipe keyseat Very bad borehole conditions

7 Borehole Quality

8 Structural Analysis 250 m

9 Structural Analysis

10 Structural Analysis Sh max DITF Tensile fractures Breakouts Sh min DITF and Breakouts 1 m Travel-Time Amplitude

11 Structural Analysis Changes in in-situ stress orientations down a borehole infer local variation in the stress field suggesting recent activity of faults or fault zones Affects the dominant fracture orientation and thus potentially fluid flow pathways in a reservoir Active fault Rotation of Sh max and Fracture strike Sh max Main fracture strike Above the fault Sh max Main fracture strike Below the fault

12 Stratigraphic Refinement Refinement of lithological and stratigraphic boundaries Acoustic amplitude Ignimbrite Conglomerate 20 m

13 Stratigraphic Refinement Observation of internal structures 5 m

14 Core Correlation Core orientation to extract maximum data Quality control of acoustic images 1 cm Determination of relationships between fracture fill and image characteristics Acoustic Image Core picture side 1 Side 2 Core tracing 1 m

15 Permeability Analysis Fluid Velocity Temperature Profiles Heat-up / Pressure Profiles Fracture density / Fracture width Fracture orientation Depth

16 16

17 3D Modelling Visualisation of results New input for fault modeling Multi-well correlation Direct use: well targeting, complement of the regional geology.

18 Potential Data Use and Future Work Geomechanics - Rock property testing - Stress magnitudes - Critical stress permeability - Well planning Tool development - Utilise NZ as testing ground for new tool development Improved interpretation - Combined tool data - Improved processing techniques

19 Conclusion High temperature geothermal logging is currently a powerful tool for: Determining borehole quality Structural characterisation of resources Refining stratigraphy Qualifying secondary permeability Limited well targeting and field management With future advancements in tools and data manipulation: Field management - geomechanical models Risk mitigation - borehole collapse etc. Quantification of permeability EGS application: better understanding fracturing processes in the TVZs low permeability basement Deep Drilling Projects: Begin to explore New Zealand s hotter and deeper geothermal resources Further development of high temperature logging tools and advanced processing techniques data becomes increasingly useful