AS3D goniometer : a powerful tool for cored-based structural analysis.
Core CT Scanning: 3D imaging for a deeper formation evaluation.
Presented by: Marco Azevedo & Mathilde Rousselle LPS, New Technology Seminar 2016
RIGHT SOLUTIONS | RIGHT PARTNER Contents
A. AS3D Goniometer B. Core CT Scanning
• Introduction • Introduction • • Work flow CT principles • Equipment • Applications • Applications • Final Considerations • Final Considerations
C. Conclusions Introduction – Data types available
This is the scale we work on!
Geomechanical Well Data Core Data and Geometrical Seismic Data Data • Image logs; • Geometrical analysis of • Geomechanical • Pre-stack attributes; • Well test; fractures; modelling; • Post-stack attributes; • Production data; • Fracture density / • Spatial distribution of frequency; stress and strain: • Fracture porosity and • Reservoir geometry; permeability; Introduction – Why core-based structural analysis?
Tectonic history and evoluiton of the reservoir >60% of the world reservoirs are fractured Understand fracture networking
Fractures and poro-perm modelling
Why do Undersampling structural analyis on core? Misinterpretation
“Skewing” effect of the data
Image-based analysis Low resolution alone is not reliable Resistivity dependent (some) Workflow – Before data acquisition
Pump out Mark the Open the Clean the Check the the inner reference liner core connection barrel line
Core fitting and marking the reference line are the most important stages All measurements will be based on the reference line
Reliable fracture orientation Workflow – Data acquisition
AS3D tool-system Workflow – AS3D
The AS3D system is a computerized goniometric tool-system that helps the structural geologist by allowing:
Geometrical Analysis Fast, efficient Qualitative Description and accurate -Depth; Quantitative Description fracture logging -Azimuth; -Typology/Nature of -Dip; structures; -Length; -Linear orientations. -Filling and mineralisation; -Aperture; -Planar shape; -Abutting; -Intersections; -Stylolite amplitude; -... -Filling percentage by typology; -... Workflow – AS3D
The AS3D system is the most sophisticated and efficient geometrical measurement tool for study of cores in the market.
Fully portable system composed by: 3D Digitiser, Stylus, A careful revision of core fitting and connection as well as Computer, Cylindrical Rollers and Table. drawing of the master orientation line are required in order to have the best structural data acquisition.
Also capable of acquiring High precision three-dimensional digitization of all planar linear orientation along planar features, tectonic and sedimentary. features.
8 Workflow – AS3D
The AS3D system holds an intuitive, flexible and editable software with several quality control mechanisms.
Instant acquisition of all geometric Management module for geological features characteristics of geological planes. description.
Immediate data storage with an Constant revision and quality integrated database. control of all acquired data
9 Workflow – Data Reorientation
• Acquired data is plotted on stereonets for each reference line. 1st Step
• Stereonets are reprocessed to find the most coherent geometric orientation of the structures 2nd Step within all core.
• Reorientation to the true geographic position, using 3rd Step well deviation info or BHI data. Workflow – Data Reorientation
Schematic process of reorientation
Example: deviated well drilled in a subhorizontal sedimentary sequence. Layers should be visible on the core (in red on the Core Borehole drawing). Apparent dip in Vertical position Well azimuth (a) and inclination (d) should also be known.
h h ic Reference planes w t h e u n z im f l a a o l p e e ” a th i d tic s s o l d e r in g h to V t a h i o n “ i n g c h e n t f t i e o o r e th
inclination
2nd step: correction from the angle of the deviation.
BROKEN ZONE Reference layers return to horizontal position
1st step: rotation around the core axis .
3rd step: correction from the azimuth and the angle of the Well.
Aspect of the core taken from the deviated well. Aspect of the core in real position. These operation give then the true orintation of all tectonic and sedimentary structures on the cores. Workflow – Data Reorientation
Reorientation using BHI data
Interpreted logging data in real position
55 data
Raw cores data, reference line is not the true North
Reorientation
Final cores data in real position to North Workflow – Graphical Outputs
13 Workflow – Graphical Outputs Composite logs
Our data Applications – Core Data – Image Data Integration
Integration between core data and image data is made using detailed photos and graphical outputs. IMAGE LOG CORE Applications – Structural Geology Interpretation
Schematic structural geology sections with integration of core data into geological maps and study of the main stages of deformation can be done. Applications – Statistical Analysis
Statistical analysis between all data acquired from core with the AS3D tool- system.
100 Bedding 80 Stratification joint 60 disconformity
40 Strati glidding Fault 20 Partially open fracture 0 Cemented fracture 8 9 10 11 12 13 14 15 Core number Applications – True frequency vs Density
Frac /m Frac/m Frac/m 0 10 20 30 40 50 60 0 10 20 30 40 50 60 0 10 20 30 40 50 60
2534 2534 2534
2535 2535 2535 Family 1: N120 Family 2: N05 Family 3: N70
2536 2536 2536
2 2 2
e e e
r 2537 r 2537 r 2537
o o o
C 2538 C 2538 C 2538
2539 2539 2539
2540 2540 2540
3892 3892 3892
3 3
3
e e 3893 e 3893 3893
r
r r
o o
o
C C 3894 C 3894 3894
3895 3895 3895
4 4
4
e e
e
3896 r 3896 r 3896
r
o
o o
C C C 3897 3897 3897
3940 3940 3940
3941 3941 3941
3942 3942 3942
3943 3943 3943
3944 Fractures measured : 64 3944 Fractures measured : 16 3944 Fractures measured : 25 Fractures calculated : 285.1 Fractures calculated : 61.6 Fractures calculated : 95.2 3945 3945 3945
5
5 5
3946 3946 3946
e e e
r r r
o o 3947 o 3947 3947
C C
C 3948 3948 3948
3949 3949 3949
3950 3950 3950
3951 3951 3951
3952 3952 3952
4005 4005 4005
4006 4006 4006 N49 4007 4007 4007
6 6 4008 6 4008 4008
e e e N124
r
r r
o o 4009 o 4009 4009
C C C 4010 4010 4010 N174 4011 4011 4011 Strike rose diagram of Open 4012 4012 and Partially open fractures. 4012
4013 4013 4013
Fracture frequency (calculated) Fracture density (measured) Applications – Porosity-Permeability Modelling
Porosity in % Permeability K in millidarcy Permeability vectors (K1 and K3) orientation can be modelled in order to calculate the optimal drilling direction in case of injector (K1) or producer (K3) wells.
% porosity
K1 K2 K3 Applications – Maximum Horizontal Stress
Based on geometric information of induced fractures it is possible to calculate the actual maximum horizontal stress.
Strata Pax Core Bit Core e
a d b c Vertical Stress Array
Core Cut Line A schematic illustration of bit-induced stress stray array below core, modified from Jaeger & Cook, 1979 (After Lorenz and Finley, 1979) Final considerations
The AS3D tool-system allows:
• Reliable orientation of tectonic & sedimentary structures with real time outputs;
• Characterisation of natural fracture connectivity by utilising information on fracture orientation, fracture size and fracture density;
• Determination of the in-situ horizontal stress and relation between induced and natural fractures;
• Comprehensive study of deformation mechanisms and evolution;
• Fracture porosity and permeability estimation;
• Prediction of optimal drilling direction in order to maximise production/injection performance; Introduction – CT imaging
• Non destructive • Mineral phases – Fluid - Air mapping • CT scanning in geosciences since mid-80’ • Extensive research and advanced techniques: – Micro and nano-CT – Image reconstruction – Image processing and analysis: from a visual tool to a quantitative tool – Dual energy analysis Larger range of applications for deeper formation evaluation Geology, Petrophysics, Enhanced Recovery process Contents
• CT principles – X-ray attenuation; – Image reconstruction; – Density mapping
• Equipment – Helical Aquilion CX 64 slices – High resolution – 3D slices
• Applications – Core, preserve, plug visualisation; – QA, QC, sample selection, slabbing; – Structural geology, Petrophysics, correlation with BHI
• Structural analysis: CT scan vs. BHI vs. Core based analysis
• Conclusion
23 1. CT principles – Computed Tomography CT scanning = multiple angles X-radiography
X-ray beam cone
64 detectors
Attenuation dependant of material densities and X-rays energy • Denser material = Stronger attenuation • X-ray attenuation by photoelectric absorption (50-100KeV) by Compton scattering (>100KeV)
24 1. CT principles – Image reconstruction
Raw Data = X-ray beam intensity I Reconstruction
Processed Data = images mapping the CT densities on each element of volume
i µi, µw: linear attenuation coefficients of material i, water [H, Hounsfield unit]
2D-3D slices
25 2. Equipment
ALS is the only Oil & Gas UK Lab with in-house Helical CT scanner - Aquilion™ 64 Toshiba
• High energy & intensity X-ray (250mA -135kV)
for better resolution/contrast
• Cone beam = 3D images
• 64 X-ray detectors = high speed scan, 1 slice/0.5mm
• Large range of sample sizes
Diameter: 1” plug to 5.25” core in liner
Max. length: 1.20m
Non destructive and fast technique for density mapping High quality 3D CT images 2. Equipment - Output
Aquilion 64: high quality 3D images
• 3D images - 1 slice every 0.5mm
• High Resolution
• Good quality in contrast of density
• Different reconstructed images available
spatial resolution vs. contrast vs. artefact/noise correction 3- Applications – qualitative, visualisation
CT images reflect the density of rock matrix, fluids and the distribution of fractures and porosity (macro)
Core/Preserve visualisation
Formation damage
Changes in lithology, matrix heterogeneity and density
Selection of preserves/plugs from core
Preserves QA/QC, inspection
Structural analysis
Slabbing orientation
Correlation with Borehole imaging (resistivity) 3- Applications - qualitative Plug/SWC
QA/QC before or after SCAL or geomechanical testing 3- Applications – density logs
He Porosity = 13% He Porosity = 25% He Porosity = 26% 3- Applications – Advanced Image analysis
3D Fractures/Lithological units Porosity segmentation Virtual Plugging segmentation+ geometrical analysis
CT Porosity 14% vs. He Porosity 16.5% 3. Applications – Petrophysics, Reservoir Engineering
Porosity, Permeability, Core flooding evaluation
• Porosity based on CT scanning – dry / saturated core
• Core flooding and EOR process evaluation
• Acid wormhole in carbonates – more effective stimulation
• Hydraulic fractures orientations
Pore scale imaging
• Micro, nano CT scan: pore space characterisation, interaction fluids-grains
• Fluid dynamics, permeability
Dual Energy scanning – true density (g/cm3), effective atomic number 3. Structural analysis - Core based analysis vs. CT scan vs. Borehole Data
Core based observation High resolution Borehole micro- + AS3D CT scan resistivity
Number structures 60 50 6 picked Mineralogy, grain size, Parameters fractures, colours, acid Phases Density Formation Resistivity reaction, hardness, etc. Spatial <0.1 mm ~ 0.2 mm 3-5 mm Resolution • Detailed charact. of • Volumetric view of all • On full borehole sed. & struct. features core • Quick data • Fast, efficient data • Ability to distinguish orientation Advantages acquisition (planar and bedding within a similar linear features) lithological unit • Accurate geometrical • Full view of fractures’ reorientation shape & connectivity • Only on cored intervals • Only on cored intervals • ‘Skewing’ effect • Only on connectable • Density dependant • Undersampling segments of core • Validation of core • Resistivity Limitations connectivity and data dependant (some) orientation • Slower picking • Slower picking 3. Structural analysis - Core based analysis vs. CT scan vs. Borehole Data 4- Final considerations
CT scan imaging
• 3D visualisation = help for the representation and modelling of geological formations and structures
• CT density logs can be correlated with Gamma-ray, Formation resistivity, etc. logs
• Up-scaling of RCA/SCAL data, micro-CT scan data
• Visualisation of transport mechanisms, fronts
Valuable information for a deeper understanding of the reservoir capacity, productivity and enhanced recovery processes Final Conclusion
• Integration of AS3D goniometric tool-system and Core CT Scanning data provide a deeper understanding of formation:
• Structural framework and distribution;
• Lithology variation;
• Porosity/Permeability;
• Grain size;
• Etc.
• AS3D and CT Scanning data can be used in reservoir characterization and modelling and integrated with other data (e.g. petrophysical analysis, seismic, etc) for bigger scale analysis of reservoirs.
• ALS Oil and Gas has exclusive use of the AS3D goniometric tool-system developed by CORIAS;
• ALS Oil and Gas is the only core laboratory in the UK operating a CT Scan and is the only laboratory offering such combined and complementary in-house services.