1. Types of Data Lecture 3 Mega-Regional Local Present Circulation
Plate Reconstructions
Maps showing Features
SLIDE 1
This unit covers the main types of data that we use in industry
The scale of the data goes from mega-regional (e.g., major lithospheric plates) to microns (e.g., pores in reservoir rocks viewed with SEMs)
Outcrops
Local
Cores
Logs
Well-Seismic Ties
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L 3 - Types of Data

2. Data Types Vary with Scale
From a basin-scale analysis to a field-depletion study, we want to integrate information from all available sources
Regional Analysis
Basin Analysis
Block Analysis
Prospect Analysis
Field Analysis
Compartment Analysis
Mega-Regional
SLIDE 2
For exploration we may start with regional studies, developing an understanding of the factors influencing tectonics and sedimentation in the basin we are working
As fields are discovered and we move into development and then production, we focus on studies of much finer-scale
For each reservoir, how will fluids move as we produce oil & gas?
Where are the flow barriers and baffles – such as thin shale layers that may segment the field vertically or small faults that might segment the field horizontally (compartments)
Fine-Scale
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L 3 - Types of Data

3. Late Jurassic to Aptian
Mega-Regional Data
Geologic Maps
Plate Tectonics
Gravity & Magnetics
Regional Seismic Lines
Tectonic Evolution
Stratigraphic Charts
Paleogeographic Maps
Etc.
• Maast. to Present
Open marine
Cen. to Maastrictian M A R I N E A N O X I C
Albian to Cenomanian C A R B O N T E M A R I N E
Aptian G U L F
Mitchum et al., 1977b
SLIDE 3
At the mega-regional scale, we would develop and use:
Geologic maps
Plate reconstructions
Gravity & magnetic data and models
Available seismic lines – typically long, regional lines
A model of the tectonic evolution of the basin
A stratigraphic chart that summarizes deposition and highlights potential source, reservoir and seal units
Paleogeographic maps
And other information that will help use understand the controls on any hydrocarbon systems
Late Jurassic to Aptian R I F T
AAPG©1977 reprinted with permission of the AAPG whose permission is required for further use.
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L 3 - Types of Data

4. Mega-Regional Analysis
Usually mega-regional analysis is performed to :
Decide which basins hold sufficient potential
Determine how much to bid for blocks
Provide regional settings to help understand the characteristics of a field
To guide step-out wells, i.e., those that extend beyond a known field in search of a similar HC accumulation
SLIDE 4
The typical goals of mega-regional analyses are to:
Decide which basins hold sufficient potential
Determine how much to bid for blocks
Provide regional settings to help understand the characteristics of a field
Guide step-out wells, i.e., those that extend beyond a known field in search of a similar HC accumulation
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L 3 - Types of Data

5. Outcrop Studies (age-equivalent or analogs)
Local Data - Surface
Surface Measurements/Observations
Topographic/Bathymetric maps
Surface geology (structure & stratigraphy)
Nearby outcrops (or analogs)
Heat flow measurements
HC seeps
Etc.
Measured
Sections
20 ft
Outcrop Studies (age-equivalent or analogs)
SLIDE 5
Another main type of data is what we can gather from the surface, either from field measurements and observations or from remote sensing (e.g., satelite data)
These data include:
Topographic/Bathymetric maps
Surface geology (structure & stratigraphy)
Nearby outcrops (or analogs)
Heat flow measurements
HC seeps
Etc.
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L 3 - Types of Data

6. Local Data - Subsurface
Subsurface Measurements/Observations
Data from Wells
cores, cuttings, logs
lithology, ages, geochem, etc
Geophysical Data
Seismic (2D, 3D, 4D)
Gravity & Magnetics
SLIDE 6
A major source of data is subsurface measurements and the resulting interpretations
Subsurface Measurements/Observations
Data from Wells
Rock samples from cores and cuttings
Measurements from subsurface rock units via logs
Interpretations of lithology, ages, geochem, etc.
Geophysical data, usually collected at the Earth’s surface
Seismic data (2D, 3D, 4D)
Gravity & Magnetics
Logging a Well
Vibrators – Seismic Sources
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L 3 - Types of Data

7. Data from Wells Samples Measurements Conventional Cores Sidewall Cores
Cuttings
Measurements
Wire-line Logs
Pressure
Temperature
Fluid samples
Flow Properties
Vertical Seismic Profiles (VSP)
SLIDE 7
Data from wells comes from rock samples and measurements at depth from the well bore
Data from samples includes those from:
Conventional Cores
Sidewall Cores
Cuttings
Data from measurements taken in the well bore include:
Wire-line Logs
Pressure
Temperature
Fluid samples
Flow Properties
Vertical Seismic Profiles (VSP)
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L 3 - Types of Data

8. Well Samples: Conventional Cores
Coring apparatus positioned at the bottom of the drill stem
Often gets intact samples of 1 meter or more
Good for analyzing lithology, sedimentary features, porosity, permeability, paleontology (ages, environments)
Interval is cored ‘blind,’ i.e., before the interval is logged
Expensive (2 round trips for the drill stem = lots of rig time)
SLIDE 8
Our best subsurface data comes from conventional cores
The coring apparatus is positioned at the bottom of the drill stem
We often get intact cores of 1 meter or more
Cores are good for analyzing lithology, sedimentary features, porosity, permeability, paleontology (ages, environments)
One drawback is that we have to core ‘blindly,’ i.e., we have to decide where to take a core before the interval is drilled and logged
Another drawback is that cores are very expensive
To take a core, we have to
pull out the drill stem
Attach the coring device and lower the drill stem (1 round trip)
Obtain the core and pull the drill stem again
Detached the coring device and send the drill stem down again (a second round trip)
All of this takes a lot of time, which is expensive (about $1 million per day)
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L 3 - Types of Data

9. Well Samples: Sidewall Cores
Small samples
(1 x 2.5 inches)
30 samples per run
Sampling based on logs
Step 1:
Gun in position
Step 2:
Shot fired
Stabilizer
Gun Body
Core Barrels
SLIDE 9
This slide explains what a sidewall core is
The tool (pictured on the left) is part of the drill stem
It has about 30 casings that can be fired into the formation
The casing captures a small sample of rock
The samples are retrieved at the end of a logging run
This does not require very much extra rig time – so is relatively inexpensive
The drawback is that the sample is small – we get the rock type but nothing about vertical variability, sedimentary structures, etc.
Step 3:
Core retrieved
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L 3 - Types of Data

10. Well Samples: Cuttings
The ‘rubble’ that comes up the sides of the well bore with the circulating fluid
Can provide samples for certain kinds of analysis – e.g., lithology, paleo
Not suitable for porosity, permeability, sedimentary structures (pulverized)
Very inexpensive – no lost rig time
PROBLEM – no control on the depth from which the samples came from – any zone not cased
SLIDE 10
Cuttings are the ‘rubble’ that comes up the well bore and reaches the surface
Think of drilling into a block of wood
Shavings of wood come up as you drill down
In general, the shavings indicate the property of the wood being drilled – with a built in delay
The delay relates to the time it takes for a shaving cut at the drill tip to move up to the surface
Cuttings are the rock ‘shavings’
There is a delay related to the time it takes for ‘shavings’ cut at a certain time (say high noon) to reach the surface – a distance that can be several thousand feet
Another problem is that cuttings do not all come from the bottom of the hole
As drilling proceeds, material can break free anywhere along the well bore and get mixed in with the ‘bottom of the hole’ cuttings
So the drilling operations are not delayed at all (~ no cost)
BUT there is a lot of uncertainty about the depth from which the material came from
The material is also pulverized, so we can not get rock properties such as sedimentary structures, porosity and permeability
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L 3 - Types of Data

11. Well Measurements: Wire-line Logs
A well log is a record of one or more physical measurements as a function of depth in a borehole
Gamma Ray
Resistivity
Density
Depth
SLIDE 11
There are many ‘tools’ that can be lowered into a well bore to take measurements
Usually a section is drilled, a string of tools is lowered to the (current) bottom, and measurements are recorded as the tools are slowly pulled up the well bore
Some tools work only before the well bore is lined with steel casing – called open-hole logs
Other tools can work in cased holes
In the old days, the measurements were recorded on a strip of paper that was registered by the depth of the toll as the measurements were made – a log (right image)
Now everything is captured digitally, but the data are still displayed as ‘logs’
Photo on left some the wire-line on a drum
The tools are attacked to the end of the wire-line and lowered into the well bore
The wire-line is pulled back and measurements are recorded.
The rotation of the drum is calibrated to translate into the depth of each tool as measurements come in
The white/blue building houses the recording equipment and the operator
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L 3 - Types of Data

12. Examples of Logging Tools
SLIDE 12
This photo show SOME of the tools that can be used to take measurements
We will discuss several of these tools and what they measure in Unit 4
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L 3 - Types of Data

13. Property What Logs Measure Lithology/Mineralogy Porosity Fluid Type
Fluid Saturation
Permeability
Stratigraphy
Downhole Pressure
Density
Acoustic Velocity
SLIDE 13
As a preview of Unit 4, here is a list of some of the rock and fluid properties that we can measure/interpret in a typical logging run
The recorded data often have to be processed and then interpreted to get the rock and fluid properties
In many cases, several logs are analyzed jointly to get information
Log analysis is a complex procedure, larger companies have experts that spent their entire career analyzing well logs
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L 3 - Types of Data

14. Objective: Analogy: Geophysical Data
Take measurements at the surface that give us an image of the subsurface
Analogy:
A sonogram
SLIDE 14
Geophysical methods provide us with a wealth of data about the subsurface
Well data is more direct and detailed than the data we get from geophysics
The problem with well data is that it gives us information at or close to the well bore – what about locations not near a well?
The biggest advantage of geophysical data is that we can obtain data over very large areas
The objective:of geophysical data is to take measurements at the Earth’s surface that will give us an image of the subsurface
As a analogy, think of a sonogram
We may want to get an image of a baby in a womb
The technology for this has many parallels to imaging the subsurface:
Sound waves are used to get the image
Sound travels down through the mother’s tummy
Some of the sound waves are reflected (bounce off) the baby’s surface
Data processing ‘focuses’ the sound waves bouncing off the baby to give us an image
Unit 5 goes into more detail on how we use sound waves (acoustic energy) to image the subsurface
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L 3 - Types of Data

15.  Seismic Data .3 s .1 s .5 s 0 s .2 s .4 s .6 s .7 s .8 s 0 s Energy
Some Energy is Reflected
Most Energy is Transmitted
Energy
Source
.1 s
.5 s
Some Energy is Reflected
Most Energy is Transmitted 
An Explosion!
0 s
.2 s
.4 s
Listening Devices
.6 s
.7 s
.8 s
0 s
SLIDE 15
As a preview of Unit 5
We use an energy source at the surface – such as a dynamite explosion
Sound waves propagate in a radial fashion down through the Earth
At major rock boundaries (more detail in Unit 5) a small part of the acoustic energy is reflected – most is transmitted (continues downward)
We have “listening” devices at the surface
In this simple cartoon, the left device “hears” acoustic energy that bounces off the top of the orange layer at 0.4 seconds
The right device “hears” acoustic energy that bounces off the top of the brown layer at 0.8 seconds
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L 3 - Types of Data

16. Raw Seismic Data For the explosion we just considered ...
Device #1
Device #2
For the explosion we just considered ...
Time
0.0
0.1
0.2
0.3
0.4
Listening device #1 records a reflection starting at 0.4 seconds
Listening device #2 records a reflection starting at 0.8 seconds
0.5
0.6
0.7
0.8
SLIDE 16
This shows the raw data recorded by the two “listening” devices on the previous slide
The acoustic wave is recorded at device #1 at 0.4 seconds
The acoustic wave is recorded at device #2 at 0.8 seconds
To image the subsurface, we use hundreds of shots (explosions) and millions of receivers (listening devices) arranged in lines either on land or offshore
To Image the Subsurface, We Use Many Shots (explosions)
and Many Receivers (listening devices)
Arranged in Lines either on Land or Offshore
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L 3 - Types of Data

17. From Raw Data to an Image
Field Record
(marine)
Data Processing
Stream
Offset
Time
SLIDE 17
This first image shows what the raw seismic data for one “explosion” recorded at about 50 “listening” devices looks like
The raw seismic data is sent to a data processing center
Here specialists in signal analysis, data analysis, imaging, math, computer science, etc. transform the raw data into an image of the subsurface
Again at large companies, there are many experts in data processing that can spend an entire career processing seismic data
Seismic imaging is an area that remains a focus of R&D – obtain better images faster and cheaper
We cover some basics of data processing in Unit 5
Once the data are processed and we have an image of the subsurface, the next step is to interpret the data – turn images such as the one in the lower right into a model of the subsurface rocks and fluids
Several Units focus on sesimic interpretation and data anlysis
Subsurface
‘Image’
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L 3 - Types of Data

18. Gravity & Magnetic Data
Instruments measure the local gravity and magnetic field
Data are processed to highlight local anomalies (residual maps)
Bodies with anomalous density or magnetic susceptibility are modeled/interpreted
SLIDE 18
Seismic data accounts for 90%+ of geophysical data collection dollars each year
There are other geophysical data types
The other two main geophysical data types are gravity data and magnetic data
Gravity data is used to interpret the density structure within sedimentary basins and the underlying lithosphere
Magnetic data gives us information on magnetic susceptibility within sedimentary basins and the underlying lithosphere
G&M data is often used to map “basement” and thus get the total sediment thickness for an area
G&M data can also help locate bodies with anomalous densities or magnetic susceptibilities
An example of a body with an anomalous density is a salt dome
An example of a body with an anomalous magnetic susceptibility is a volcanic sill
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L 3 - Types of Data