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 S O L U T I O N S RIGHT PARTNER
Contents A. AS3D Goniometer Introduction Work flow Applications Final Considerations B. Core CT Scanning Introduction CT principles Equipment Applications Final Considerations C. Conclusions
Introduction Data types available This is the scale we work on! Well Data Core Data Geomechanical and Geometrical Data Seismic Data Image logs; Well test; Production data; Geometrical analysis of fractures; Fracture density / frequency; Fracture porosity and permeability; Geomechanical modelling; Spatial distribution of stress and strain: Reservoir geometry; Pre-stack attributes; Post-stack attributes;
Introduction Why core-based structural analysis? >60% of the world reservoirs are fractured Tectonic history and evoluiton of the reservoir Understand fracture networking Fractures and poro-perm modelling Why do structural analyis on core? Undersampling Misinterpretation Skewing effect of the data Image-based analysis alone is not reliable Low resolution Resistivity dependent (some)
Workflow Before data acquisition Pump out the inner barrel Open the liner Clean the core Check the connection Mark the reference 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 -Depth; -Azimuth; -Dip; -Linear orientations. Qualitative Description -Typology/Nature of structures; -Filling and mineralisation; -Planar shape; -Intersections; -... Quantitative Description -Length; -Aperture; -Abutting; -Stylolite amplitude; -Filling percentage by typology; Fast, efficient and accurate fracture logging -...
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, Computer, Cylindrical Rollers and Table. A careful revision of core fitting and connection as well as drawing of the master orientation line are required in order to have the best structural data acquisition. High precision three-dimensional digitization of all planar features, tectonic and sedimentary. Also capable of acquiring linear orientation along planar features. 8
Workflow AS3D The AS3D system holds an intuitive, flexible and editable software with several quality control mechanisms. Instant acquisition of all geometric characteristics of geological planes. Management module for geological features description. Immediate data storage with an integrated database. Constant revision and quality control of all acquired data 9
Workflow Data Reorientation 1st Step Acquired data is plotted on stereonets for each reference line. 2nd Step Stereonets are reprocessed to find the most coherent geometric orientation of the structures within all core. 3rd Step Reorientation to the true geographic position, using 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 drawing). Well azimuth (a) and inclination (d) should also be known. Core Borehole Apparent dip in Vertical position Ve r t ic a l p la n e w h ic h c on ta in s t he a z im ut h o f t h e h i g h sid e o f t he o rie nt ing to ol d Reference planes 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 toolsystem. 100 80 60 40 20 0 8 9 10 11 12 13 14 15 Core number Bedding Stratification joint disconformity Strati glidding Fault Partially open fracture Cemented fracture
Applications True frequency vs Density Frac /m Frac/m Frac/m 30 40 30 40 30 40 0 10 20 50 60 0 10 20 50 60 0 10 20 50 60 2534 2534 2534 2535 2535 2535 2536 2536 2536 Family 1: N120 Family 2: N05 Family 3: N70 Core 4 Core 3 Core 2 2537 2538 2539 2540 3892 3893 3894 3895 3896 3897 Core 4 Core 3 Core 2 2537 2538 2539 2540 3892 3893 3894 3895 3896 3897 Core 4 Core 3 Core 2 2537 2538 2539 2540 3892 3893 3894 3895 3896 3897 3940 3940 3940 3941 3941 3941 3942 3942 3942 3943 3943 3943 3944 3945 Fractures measured : 64 Fractures calculated : 285.1 3944 3945 Fractures measured : 16 Fractures calculated : 61.6 3944 3945 Fractures measured : 25 Fractures calculated : 95.2 Core 5 3946 3947 Core 5 3946 3947 Core 5 3946 3947 3948 3948 3948 3949 3949 3949 3950 3950 3950 3951 3951 3951 3952 3952 3952 4005 4005 4005 4006 4007 4006 4007 N49 4006 4007 Core 6 4008 4009 Core 6 4008 4009 N124 Core 6 4008 4009 4010 4011 4010 4011 N174 4010 4011 4012 4012 Strike rose diagram of Open 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. Vertical Stress Array Core a b c Strata Pax Core Bit d e 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 [H, Hounsfield unit] i µ i, µ w : linear attenuation coefficients of material i, water 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 segmentation+ geometrical analysis Porosity segmentation Virtual Plugging 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/cm 3 ), effective atomic number
3. Structural analysis - Core based analysis vs. CT scan vs. Borehole Data Core based observation + AS3D High resolution CT scan Borehole microresistivity Number structures picked Parameters Spatial Resolution Advantages Limitations 60 50 6 Mineralogy, grain size, fractures, colours, acid reaction, hardness, etc. Phases Density Formation Resistivity <0.1 mm ~ 0.2 mm 3-5 mm Detailed charact. of sed. & struct. features Fast, efficient data acquisition (planar and linear features) Accurate geometrical reorientation Only on cored intervals Only on connectable segments of core Volumetric view of all core Ability to distinguish bedding within a similar lithological unit Full view of fractures shape & connectivity Only on cored intervals Density dependant Validation of core connectivity and data orientation Slower picking On full borehole Quick data orientation Skewing effect Undersampling Resistivity dependant (some) 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.