petrophysics workflow
TRANSCRIPT
Petrophysics WorkflowPetra® User Group Session Series
Armin Schafer
Technical Sales Executive
PETRA/PetraSeis/GeoSyn
Encana Amphitheatre
Oct 20, 2011
noon – 1 pm
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Petra® User Session Agenda
• News and Announcements
• Petrophysics Workflow • Intro – what is Petrophysics
• Importing Digital Data
• Digital Logs QA/QC
• Log Calculations
• Log Generation
• Refine / Reiterate
• Questions
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PETRA® User Session Agenda
• News and Announcements
• Petrophysics Workflow
• Questions
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Petrophysics Defined
What is Petrophysics?
Petrophysics (petro is Latin for "rock" and physics is the study of nature) is the study of the physical and chemical properties that describe the occurrence and behavior of rocks, soils and fluids. Petrophysicists evaluate the reservoir rock properties by employing well log measurements, core measurements, and sometimes seismic measurements, and combining them with geology and geophysics. (Wikepedia)
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Reservoir petrophysical properties
Most petrophysicists are employed to compute what are commonly called
reservoir petrophysical properties. These are:
• Lithology : What type of rock is it. When combined with local geology and core study,
geoscientists can use log measurements such as natural gamma, neutron, density, Photoelectric,
resistivity or their combination to determine the lithology downhole.
• Porosity ϕ: The amount of pore (or fluid occupied) space in the rock. This is typically
measured using an instrument that measures the reaction of the rock to bombardment by neutrons
or by gamma rays. Sonic wave speed and NMR logs are also measured to derive rock porosity.
• Water saturation Sw: The fraction of the pore space occupied by water. This is typically
measured using an instrument that measures the resistivity of the rock.
• Permeability: The quantity of fluid (usually hydrocarbon) that can flow from the rock as a
function of time and pressure. Formation testing is so far the only direct downhole permeability
measurement. In case of its absence, which is common in most cases, permeability estimation is
derived from other measurements, such as porosity, NMR, sonic, by empirical correlations.
• Net Pay: Thickness of rock that can deliver hydrocarbons to the well bore at a profitable rate.
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Petrophysics Wireline logs
Example from Wikepedia (author Andy May)
Petra example
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Petra® Petrophysical Workflow Goals
• Automate petrophysical analysis and speed up
interpretation
• Biggest challenge is data handling• Best → KISS principle
• Log mnemonics reduced to minimal/optimal numbers
• Smart use of filtering, renaming and merging of normalized curves
• Workflows will be different based on work styles, areas of
expertise & allocated resources
• Ideal vs. practical
• Available HR and time
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Petra® Petrophysics Workflow
1. Import Relevant Digital Data
2. Verify Data QA/QC
3. Log Generation
4. Log Calculations
5. Refine / Reiterate
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Petra® Petrophysics Workflow
1) Import Relevant Digital Data
Digital Curves (via Direct Connect, Single LAS or Batch LAS)
Directional Surveys (via Direct Connect, Well-by-Well or Batch Ascii)
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Importing Digital logs
Single or Batch LAS Direct Connect
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Importing Digital Data
Skip Duplicates
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Importing Digital Data
Resample / Rename if Curve Exists
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Importing Digital Data
Convert Units
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Importing Digital Data
Curve Translation File
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Directional Surveys – Well-by-Well CSV
If possible, import Azimuth and Inclination data as this cannot be back-calculated within PETRA.
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If possible, import Azimuth and Inclination data as this cannot be back-calculated within PETRA.
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Directional Surveys – Import tabular ASCII File
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Petra® Petrophysics Workflow
2 Verify Data QA/QC
Garbage in = Garbage out
Log Aliasing
Checking Units/Scales
Log Histogram & Statistics
Normalization
Advanced Log Transforms
Log Merging
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Corporate or Project based strategy for data
imports
• Companies often have best practices – eg use decimal vs percentage for porosities, use .1 for sample rate
• Key is to be consistent
• Be aware of who is doing the updates and what data is being updated
• – where did the data come from – define source field of data.
• Add remarks or descriptions wherever possible.
• Always keep a copy of the original data, save changes to a new copy
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Data QA/QC
Check tool calibration and log quality
• Use correct type of curve – eg SS vs LS
• Log quality – year of log
• Service provider variation in naming
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Data QA/QC
Resampling under Advanced Log Transforms
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Data QA/QC
Resampling under Advanced Log Transforms
Keep in mind that decimating can lose data and interpolating creates new data points.
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Data QA/QC
Statistics and Log Histogram
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Data QA/QC
Statistics and Log Histogram
Data Statistics
Log Histogram
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Data QA/QC
Log Histogram
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Data QA/QC
Run statistics on curves
Stats useful for picks, cutoffs and normalization
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Data QA/QC
Check Scales and units
Check m vs feet and sample rate throughout the main module
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Data QA/QC
Merging in Log Transformations
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Data QA/QC
Merging Curves in the Log Previewer
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Data QA/QC
Log Normalization
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Data QA/QC
Log Normalization – Percentile Range
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Data QA/QC
Log Normalization – Restrict Depths/Wells
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Petra® Petrophysics Workflow
3) Log Generation
Log Equation Expression (Vshale, Water Saturation, Effective Porosity, etc.)
Crossover and Pay Flag Curves
Advanced User Models
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Log Generation
Log Equation Expression - SW
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Log Generation
Log Equation Expression – preloaded equations
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Log Generation
Log Equation Expression VSH
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Log Generation
Log Equation Expression – write your own
Can save this and share with others
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Log Generation
Advanced Transforms - Archie Water
Saturation
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Log Generation
Advanced Log Transform – Fortran scripts
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Log Generation
Advanced Log Transform – View Model
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Log Generation
Advanced Log Transform – Input and Output
Variables
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Log Generation
Compute from Logs - Crossover
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Log Generation
Compute from Logs – Pay Flag Curves
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Log Generation
Compute from Logs – Pay Flag Curves
Output Curve Tab
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Petra® Petrophysics Workflow
4) Log Calculations
Log Footage Summations
Payflag Continuity
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Log Calculations – Log Footage
Summation (Reservoir Properties)
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Log Calculations – Zone Field Name
Descriptions
Gross - Gross footage is computed using one of two methods selected in the Options Tab.
It is either the isopach thickness based on the zone's upper and lower depth or it is
summed using the GR/(Condition 4) log curve cutoff condition.
Net – Net footage is the summation of the total number of feet where the Porosity
/(Condition 1) curve passes its cutoff criteria. All checked log curve drop down boxes
cutoffs are used as cutoff criteria.
Net/Gr (NGR) - Ratio of the Net divided by Gross. You must compute Net and Gross in
order to compute Net/Gr.
Poros Ft (PHIH) - Summation of each sample interval multiplied by each Porosity/(Condition
1) curve value passing all cutoff criteria. You must also select Net with this option.
Perm Ft (KH) - Summation of each sample interval multiplied by each
Permeability/(Condition 3) curve value passing all cutoff criteria. You must also select Net
with this option.
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Log Calculations – Zone Field Name
Descriptions - continued
Hydrocar Ft (SOPHIH) - Hydrocarbon Feet is the summation of each sample interval
multiplied by each Porosity/(Condition 1) times 1.0 - Water Sat/(Condition 2) passing all
cutoff criteria. Requires porosity and water saturation curves.
Avg Poros (PHIA) - Arithmetic mean value of all Porosity/(Condition 1) curves values
passing all cutoff criteria.
Avg Perm (KA) - Arithmetic, geometric, or harmonic mean value of all
Permeability/(Condition 3) curve values passing all cutoff criteria. Select the method of
averaging in the Options Tab.
Avg SW (SWA) - Arithmetic mean value of all Water Sat/(Condition 2) curve values passing
all cutoff criteria.
User Ft - Summation of the total number of feet where all cutoff criteria are meet.
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Log Calculations – Log Footages
Depth Zones Tab
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Log Calculations – Log Footages
Options Tab
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Log Calculations – Log Footages
Capture Tab
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Log Calculations – Log Footages
Filter Tab
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Log Calculations – Log Footages
File Tab
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Log Calculations – Log Footages
Export Tab
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Log Calculations – Log Footages
Batch Tab
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Log Calculations – Log Footages
Example of Zone Items Output
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Log Calculations – Log Footages
Pay Interval Data (Other Tab Main Mod)
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Log Calculations – Log Footages
Results with criteria used
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Log Calculations – Pay Continuity
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Log Calculations – Pay Continuity
Zones and Options Tab
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Log Calculations – Pay Continuity
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Petrophysics Workflow
5) Refine / Reiterate
Plot Data and Analyze
Import New Data and Cull Old Data
Change Parameters
Document, Document, Document
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Petrophysical Curves Display Example
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Total Pay Footage Map – edit bullseyes
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Total Pay Footage Map –
check logs in X-section
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Average Continuous Pay Map
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Crossplot of NPHI vs DPHI vs Water
Saturation