The Eriboll
Formation of
A GIS database for steps to understanding fracture
patterns and
outcrop
analogues to subsurface well data.
Kira Diaz
Tushman
December 8, 2005
Overview:
The Cambrian Eriboll Formation of
Northwestern Scotland, a fractured sandstone, is an
outcrop analogue to tight gas sandstones at depth. There are many types of data that need to be
collected in order to understand the relationship between the outcrops and the
information that is readily available from a four inch well core. The difficulty in studying rocks such as
tight gas sandstones, is that there are no outcrops
that directly related to the rocks being drilled; thus finding outcrops that
show the same patterns seen in SEM/CL imagery of the core and having similar
fracture relationships is important to understanding what is truly going on at
depth. Preliminary imaging of the Eriboll Formation shows not only structures that were
before only thought of as joints caused by uplift (thus of little structural
importance), but the images also show structures that were identical to
structures found in core samples (structures such as lined fractures and
bridges).
The Problem:
The process to get from the outcrop and samples to
comparing the results to the core data from wells is a long and involved one,
usually requiring multiple people on multiple computers using multiple programs
to work together in order to produce useful results.
The Objective:
The objective is to create a fully interactive map of
The data will include:
1.
Regional
Satellite Images
2.
Digital Elevation
Model
3.
2 1:250000
Geologic Maps
4.
GPS point
location –
a.
sample location,
b.
scanline locations,
c.
image locations
This database will then be
used for
1.
Easy retrieval of
distance between samples
2.
Ease in locating
data tables, computations, results and continued work in on data processing
3.
Ease in comparing
orientations of fractures in images from North to South
4.
Comparing the
fault orientations to their type (thrust, normal, strike slip)
5.
Easy comparison
between data sets of different operators
Data acquisition:
Due to the supposed simplicity of the outcrops that are of
interest, there has been very little work done in this area. Also because my field area is not located in
the
Procedure:
1
NASA ZULU map was
downloaded from https://zulu.ssc.nasa.gov/mrsid/
by selecting the area that I wanted to download - N-30-55_2000.tar, since it
was .tar, I downloaded untar.exe. to run in dos with
the help of another student. This was
then looked at in arc catalogue – it had the spatial reference of
WGS_1984_UTM_30N and a resolution of 14.5m.
2 The DEM was downloaded from http://seamless.usgs.gov/ at 1km resolution. It was also downloaded with Cartesian Coordinates, and projected on the fly in ArcMap to the WGS_1984_UTM_30N
Figure 1: SEM layered on mrsid Satellite
image of
3
The two paper
maps (references below), need to be scanned georeferenced
and rectified onto the DEM and Satellite images. Processed followed to rectify maps are listed
in http://www.geo.utexas.edu/courses/371c/Labs/lab5.htm
and http://www.geo.utexas.edu/courses/371c/Labs/Software_Tips/Georeferencing.htm
. These directions were great when
dealing with UTM coordinates. However
due to most of the maps being referenced in British National Grid units (BNG)
it was easier to find points if I could convert between BNG and UTM: http://franson.com/coordtrans/ , this
site allows a 7 day free download, and one is able to transfer between most map
units
Figure 2: Layers from bottom to top (with transparency percentage): DEM
(0%), Satellite (50%),
southern map Great Glen (50%), northern map Sutherland (50%)
4
There are two
sets of GPS data collected over 3 years.
The older set from 2003-2004 was collected by Steve Laubach. This BNG data was written in a data table for
future use. This data was not in a
format that could be imported to GIS.
With same program listed above, I converted all the BNG points to UTM
and created a table with all pertinent data that could be imported (.dbf) (see
link for exact information to create a .dbf for GIS (http://www.geo.utexas.edu/courses/371c/Labs/Software_Tips/Exccel_to_Dbase.htm)
Figure 3: image of final excel .dbf of Steve’s
sample information
Figure 4: Basic directions to adding X Y
coordinated and setting the coordinate system.
Tools – add XY coordinates –
Chose table – Set X and Y column – edit –
Select coordinate system – UTM – WGS etc…
Figure 5: Geologic Maps with data collected
by Steve Laubach
5
The second set of
GPS data was collected by me with a person GPS unit. The geographic coordinate was selected in the
unit (WGS_UTM_30). This data was
downloaded with Mark Helper. The gps4U
shareware program created both a .dbf and a shape file that could be loaded
directly into the GIS map and assign a coordinate system.
Figure
6: Geologic maps with data collected by Kira Diaz Tushman
Data Preprocessing:
Creating required Feature classes for a new
map
Geodatabase
was created to hold all geology files
Polygons: Geologic Unit of the Eriboll
Sandstone
Polylines:
regional and local faults
Methods
for creating a Geodatabase with all feature classes
and then digitizing is located in http://www.geo.utexas.edu/courses/371c/Labs/lab5.htm
* The amount of preprocessing done is sufficient
accomplish to goals of the specific aspects of this project – however at some
later time a fully functional map that follows topology rules may be useful,
which would only involve adding new features to the map in arc catalogue and
digitizing in the dikes, other geologic layers, and the rest of the faults. *
Figure 7: Digitized Cambrian Eriboll Formation and all faults that crosscut it.
Figure 8: Attribute table created with the
faults listing orientation and type.
With the digitized polygons of the geologic area it is easy to see the square meters of outcrop that could possibly be around – This sandstone outcrops in huge bedding planes. If there is ever a satellite image with a higher resolution than 14.5 meters these bedding planes that range from 2km2 to 1m2 will be easy to see and get accurate measurements of the true area that is outcropping in a manner conducive towards scanline measurements.
Figure 9: White and Pink areas in satellite
image are Eriboll Formation outcrops. The Distance
across
this image is 4.6 km. With higher resolution satellite imagery
finding the area of the outcrops (with green
sample points on them) would be useful in the
study of the fracture patterns.
Arc View Processing:
The Arc View processing was a way to
manipulate the data in order for it to full function as an interactive
database. The computers at the BEG are
all located on the BGNets network, and as long as
files are stored in the proper folders the entire bureau can access data. This is the premise of this project – to
allow people an easy way to see all the data involving the
1 A hill shade was created from the DEM in
order to show 3D space. This procedure
was taken from http://www.geo.utexas.edu/courses/371c/Labs/Lab8.htm
however there was on difference. Due to
the type of data the x and y coordinated were recorded in the data as decimal
degrees while the z coordinate was recorded as meters. The conversion for this is 1 degree = .000009
meters.
Figure 10: How one gets to the Hillshade
Figure 11: Hillshade
text box with default settings – good if X,Y, and Z
are in the same units
Figure 12: Change in the Z factor because X and Y are in Decimal
Degrees and Z is in meters.
If left along Z would be greatly exaggerated.
Figure 13: Hillshade
layered under the satellite images (75% transparency) with the geology
layer (75% transparency) and the faults
above. The white spots are on the
satellite images where
there was no data collected.
Hyperlinking:
The
main focus of the GIS project is to have a comprehensive map. This map will have links to all the data and
results that have been collected for each sample. This type of map is most effective when there
are many network computers that store the data.
There
are two ways to hyperlink data: Field Hyperlinking and Dynamic Hyperlinking.
Field Hyperlinking
Field
hyperlinking is simply attaching a field of the
attribute table with links to documents that relate to the map. With this method you can only attach one
value to each point from the attribute table.
This is good for batch hyperlinking. If however you need to add more documents to
any specific point you need to add them with dynamic hyperlinking
(described below).
How
to Field Hyperlink
1.
In attribute
table: Options > add a field (make sure that editing toolbar is off)
2.
Have field type
be text with 200 variables
3.
Turn on editing
toolbar
4.
Put relative link
into each sample. (Ex. C:\Tushman\Field Work Data\Things accompished in the field.doc )
5.
Place link in
each blank that has something to be hyperlinked
6.
Save edits
7.
Layer >
Properties > Display tab > Hyperlinks
8.
Click support Hyperlinks
using field > drop down menu to field that has links listed
9.
Make sure
document has the black dot in front of it
10. Click OK
Figure 14: Add Field
Figure 15: Add Field dialogue box – Add a
Name, Change Type to Text, Change Length to 200
Figure 16: Properties Menu > Display tab
> Click Support Hyperlinks > Dropdown menu
and chose field with hyperlinks > click
document > click OK
** To see those points with
hyperlinks
Click lightning bolt on tool bar
The points with Hyperlinks will turn Bright Blue
Hold Lightning bolt end over point (must be end or
the hyperlink will not
show up)
Link will appear – click on link and new program
will open
Now you can edit the original document
Figure 17:By clicking Hyperlink on the Tools toolbar, points that were red are now Blue
Figure 18: Hyperlink for Point shows up
when the very tip of lightning bolt is placed on the hyperlinked point
Figure 19: Program where hyperlink was
originally created opens up, and the document can be edited and saved.
Dynamic Hyperlinking:
Dynamic Hyperlinks are very
useful when you only need to add one or two hyperlinks, or a point needs to
have more than one hyperlink. This does
not preclude field hyperlinking, nor does a point
need to have a field hyperlink before a dynamic hyperlink can be added.
How to Dynamic Hyperlink
Click the Identify tool on Tool bar
Pick point that you want to hyperlink a document to
In identify box > right click point to hyperlink
Chose hyperlink on menu
Navigate to document to hyperlink
Click Ok
*** To add more documents
REPEAT all steps until you have hyperlinked all documents for any given
point***
Figure 20: Identify tool, after a point was
clicked. Right click on point and chose
“Add Hyperlink”
Figure 21: After browsing for link to
document
See direction above to show
hyperlinks. When a point has more than
one hyperlink, click on the yellow hyperlink flag and a new box will pop
up. Chose hyperlink that you want, and the
file will open in a program that you can edit in.
Figure 22: When there is more than one
hyperlink, clicking on dot brings up this text box
Figure 23: New program opened after one document was chosen.
Results:
With all the points
hyperlinked to every bit of data ever created for them, anybody can go back to
my master’s thesis and understand what I did.
With everything organized there is no problem transferring information
from one generation of fracture research students to another. Other researchers can add to this map,
correct any mistakes and rework data for new and different problems.
References:
British Geologic Survey:
Sutherland Map: Sheet 58N 06W, Solid Edition.
Scale 1:250,000. 1989
British Geologic Survey:
Great Glen Map: Sheet 57N 06W, Solid Edition.
Scale 1:250,000. 1989
