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INTERACTIVE SANDSTONE PETROLOGY:
A 
DIGITAL
TUTORIAL FOR FUTURE RESERVOIR GEOLOGISTS*
By
Suk-Joo Choh1, Kitty L. Milliken2, and Earle F. McBride3
Search and Discovery Article # 40041 (2002)
*Adapted for online presentation, as a demonstration of the Tutorial, based on a poster session by the authors at the 2001 AAPG Annual Convention, Denver, CO. Winner of the SEPM best poster award from the 2001 Denver AAPG Convention.
* Department of Geological Sciences, The University of Texas at Austin, Texas, USA (www.geo.utexas.edu)
A new,
cost-efficient approach to teaching undergraduate-level sandstone petrography is
being devised. The main goal of this multimedia tutorial is to provide a
quantity of petrographic information sufficient to allow students to attain a
high level of expertise in rock description. Development in digital format will
permit effective delivery of the tutorial via CDs and the Internet. The tutorial
is based on a collection of high-resolution digital petrographic images and
utilizes a hierarchical menu and topics for navigation. The tutorial is composed
of modules for sandstone types and other topics. Each module is further divided
into sub-modules. Within a sub-module, forward and backward arrows, and other
navigational choices allow the user to move around and explore the contents. The
interface is dominated by the petrographic image with minimal screen space
devoted to tutorial functions. The user is able to determine the presence of an
interactive area within the image by moving the pointer across the screen until
the pointer changes from an arrow to a hand. When an active area is clicked by
mouse, relevant instructional information appears. An online glossary is
provided. Each sub-module is designed to add information gradually so that the
user fully absorbs the topic at the user’s own pace. This interactive tutorial,
which intitially will contain up to 300 interactive photomicrographs, represents
the first step towards a digital library of petrographic images that will serve
as a reference work for use in reservoir description.
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Petrography, description and
interpretation of rock properties at the microscopic scale remains,
fundamentally, a qualitative field of study highly dependent upon the
involvement of a trained observer. However, instruction in petrography
in the universities, where it is still practiced, remains largely
unchanged since the 19th century. A trend toward removing petrographic
experience from university curricula arises primarily because of
economic considerations relating to the labor-intensive character of
petrographic instruction, yet the practical value of such training
remains and is becoming a concern of industry professionals who seek to
hire students possessing basic skills in rock description (Thomasson,
2000). Preserving petrographic studies in the modern curriculum
requires that new, more cost efficient methods be devised for passing
skills from instructor to student. This project attempts partially to
mimic the highly visual and interactive character of traditional
petrographic instruction with the goal of training and motivating
students in the use of these methods. Preserving petrographic studies is
also important for the petroleum industry and service companies because
forward numerical models for risk analysis, porosity
Existing Petrographic Contents In Multimedia Format
An online search of Science Citation
Index (http://wos.isiglobalnet.com/)
reveals that The Goals Of Current Tutorial1. Expose students to a large and diverse amount of visual material, comparable to that formerly provided in petrographic laboratory activities that have been largely displaced from the curriculum. 2. Allow students to attain a higher level of expertise in rock description than current instructional practices allow by the use of substantial interpretive material and an interactive structure that will guide the student through a process that will itself promote absorption of the information. 3. Motivate students to persist in higher level petrographic studies as well as career path toward petroleum and service industries.
How To Use The Tutorial
The principle subdivisions of the
tutorial are based on the major ‘clans’ of the Folk sandstone
classification: quartzarenite, arkose, litharenite (Folk,
1974), and a fourth group of sandstones that do not fit within this
standard scheme (Figure
1). For each of these clans there are images that deal principally
with provenance and those that are primarily instructive about
diagenesis (Figure
2). Within each of the four major subsections the user has the
option to review text outlining the principal facts and themes conveyed
by the subsection (Figure
2, “Goals”) and to proceed through the tutorial images one at a time
(Figure
2, “Tutorial”), in the order they are arranged. Alternatively, all
the images within a subsection can be reviewed in a thumbnail section (Figure
2, “Browse”;
Figure 3), which allows the user to navigate to a full-frame image
at any point within the tutorial. Once the user is in one of the main
tutorials, general information on the specimen can be retrieved from the
“Info” button on the function bar (Figure
4). Active regions of the image are indicated when the cursor
changes from an arrow to a pointing hand. Clicking on such a region
calls up information (Figure
5) in one of two modes. In the first, a click brings up a short
identification of the
activated region, a tiny bit of text
that quickly disappears on its own. Clicking on the region related to
the major theme of the image retrieves a larger box of text. The user
then clicks anywhere on the image or function bar to remove this textbox
and proceed with his/her explorations. Holding a click
on an active region allows the
user to get a leisurely look at the mapped area relevant to the textbox.
An online glossary is provided by a hyper-linked textbox, which appears
in orange color with underline (Figure
5). Navigation to sequentially positioned images within tutorial
subsections is accomplished with arrow buttons on the function bar.
Plane light and cross-polar views can be toggled with “PPL/XPL” button
on the function bar (Figure
6 and
Figure 7). In some cases plane light and cross-polar views are
mapped somewhat differently, and clicking on the same regions in these
different imaging modes may activate different informational boxes. The
“History” button allows the user to create a sequential record of pages
visited in their path through the tutorial; double-clicking on any page
in this list allows the user to return to that point in the user’s trek
(Figure
8). The “Search” button allows the user to generate a list of pages
featuring an image or text relating to a particular topic; it therefore
turns the
Ongoing Activities And Future Plan
The demonstration version of the
tutorial described here is presently being evaluated in laboratory
exercises in an undergraduate-level sedimentary rocks course at the
University of Texas at Austin. A proposal currently in development
will seek to expand the tutorial content and extend the evaluation
process to other universities. Plans for future tutorial content
include: specific examples from well-known sandstone reservoirs;
inclusion of more petrographic features that play a significant role in
reservoir quality (e.g., an expanded section on clay cements);
utilization of a wider variety of petrographic image types (for example,
scanning electron and cathodoluminescence micrographs); quiz functions;
greater graphical content in the compaction and texture sub-tutorials.
Our long-term goal is linking teaching modules for sandstones and other
rocks to a major archive of images from the
University of Texas at Austin petrology collections. In fully
realized form, this AcknowledgementsSupport for the development of this tutorial has been provided by the College of Natural Sciences, the University of Texas at Austin through student-funded technology fees, and the National Science Foundation, Division of Undergraduate Education, Course Curriculum and Laboratory Improvement Program; under grant #DUE-0088763. We thank Drs. Kathie Marsaglia, Shirley Dutton, Ted Walker, and Robert Folk for reviewing the tutorial in its early stages. Luis Crespo and Petro Papazis provided assistance for image mapping. ReferencesCarozzi, A.V., 1996, Carbonate petrography: grains, textures, and case studies, in Scholle, P.A. and James, N.P. (eds.), SEPM Photo CD, Volume 9: Tulsa, Oklahoma, SEPM. Christiansen, E.H., 2001, PetroGlyph 1.0 Multimedia CD-ROM: Malden, Maryland, Blackwell Science. Folk, R.L., 1974, Petrology of sedimentary rocks: Austin, Texas, Hemphill Publishing, 184 p. Lander, R.H., and Walderhaug, O., 1999, Predicting porosity through simulating sandstone compaction and quartz cementation: AAPG Bulletin, v.83, p.433-449. Thomasson, M.R., 2000, Rocks are still key exploration clues: AAPG Explorer, v.21, p.4, 13. Walderhaug, O., 2000, Modeling quartz cementation and porosity in Middle Jurassic Brent Group sandstones of the Kvitebjorn Field, northern North Sea: AAPG Bulletin, v.84, p.1325-1339.
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