Petrophysics Workflow

Petrophysics WorkflowPetra® User Group Session Series

Armin Schafer

Technical Sales Executive

PETRA/PetraSeis/GeoSyn

Encana Amphitheatre

Oct 20, 2011

noon – 1 pm

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

PETRA® User Session Agenda

• News and Announcements

• Petrophysics Workflow

• Questions

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)

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.

Petrophysics Wireline logs

Example from Wikepedia (author Andy May)

Petra example

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

Petra® Petrophysics Workflow

1. Import Relevant Digital Data

2. Verify Data QA/QC

3. Log Generation

4. Log Calculations

5. Refine / Reiterate

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)

Importing Digital logs

Single or Batch LAS Direct Connect

Importing Digital Data

Skip Duplicates

Resample / Rename if Curve Exists

Convert Units

Curve Translation File

Directional Surveys – Well-by-Well CSV

If possible, import Azimuth and Inclination data as this cannot be back-calculated within PETRA.

Directional Surveys – Import tabular ASCII File

2 Verify Data QA/QC

Garbage in = Garbage out

Log Aliasing

Checking Units/Scales

Log Histogram & Statistics

Normalization

Advanced Log Transforms

Log Merging

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

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

Data QA/QC

Resampling under Advanced Log Transforms

Data QA/QC

Resampling under Advanced Log Transforms

Keep in mind that decimating can lose data and interpolating creates new data points.

Data QA/QC

Statistics and Log Histogram

Data QA/QC

Statistics and Log Histogram

Data Statistics

Log Histogram

Data QA/QC

Log Histogram

Data QA/QC

Run statistics on curves

Stats useful for picks, cutoffs and normalization

Data QA/QC

Check Scales and units

Check m vs feet and sample rate throughout the main module

Data QA/QC

Merging in Log Transformations

Data QA/QC

Merging Curves in the Log Previewer

Data QA/QC

Log Normalization

Data QA/QC

Log Normalization – Percentile Range

Data QA/QC

Log Normalization – Restrict Depths/Wells

3) Log Generation

Log Equation Expression (Vshale, Water Saturation, Effective Porosity, etc.)

Crossover and Pay Flag Curves

Advanced User Models

Log Generation

Log Equation Expression - SW

Log Generation

Log Equation Expression – preloaded equations

Log Generation

Log Equation Expression VSH

Log Generation

Log Equation Expression – write your own

Can save this and share with others

Log Generation

Advanced Transforms - Archie Water

Saturation

Log Generation

Advanced Log Transform – Fortran scripts

Log Generation

Advanced Log Transform – View Model

Log Generation

Advanced Log Transform – Input and Output

Variables

Log Generation

Compute from Logs - Crossover

Log Generation

Compute from Logs – Pay Flag Curves

Log Generation

Compute from Logs – Pay Flag Curves

Output Curve Tab

4) Log Calculations

Log Footage Summations

Payflag Continuity

Log Calculations – Log Footage

Summation (Reservoir Properties)

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.

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.

Log Calculations – Log Footages

Depth Zones Tab

Options Tab

Capture Tab

Filter Tab

File Tab

Export Tab

Batch Tab

Example of Zone Items Output

Pay Interval Data (Other Tab Main Mod)

Results with criteria used

Log Calculations – Pay Continuity

Zones and Options Tab

Petrophysics Workflow

5) Refine / Reiterate

Plot Data and Analyze

Import New Data and Cull Old Data

Change Parameters

Document, Document, Document

Petrophysical Curves Display Example

Total Pay Footage Map – edit bullseyes

Total Pay Footage Map –

check logs in X-section

Average Continuous Pay Map

Crossplot of NPHI vs DPHI vs Water

Saturation

Petrophysics Workflow

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