Published Illustrations in Exploration-Type Synthesis:

Example - Hackberry Sand (Oligocene)

Southeast Texas – Southwest Louisiana

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Larry D. Gerken

MASERA Corporation

1743 E. 71^st Street

Tulsa, OK 74136

 

 

 

ABSTRACT

 

Geological journals, in particular AAPG publications, contain a wealth of information that is of considerable value to the modern explorationist. These journals with full-search capabilities on the Internet or on CD-ROM permit rapid retrieval of pertinent data, including illustrations, which are of significant use. With appropriate permission, they may be altered, edited, or enhanced as an expeditious means of determining trends or prospective areas, as well as providing a general framework.

 

The procedure in using illustrations is as follows: (1) perform a search using well chosen criteria, (2) from the results list (of references) select those articles considered to be relevant, (3) retrieve illustration(s) to be used after study of pertinent articles, and (4) edit images of selected illustrations within an appropriate software package.

 

Using three illustrations from three different articles in the AAPG Bulletin, a regional isopach map was prepared of sandstone in the lower part of the Hackberry Shale (Frio) in Southeast Texas and Southwest Louisiana. This map not only shows the framework for deposition of these deep-marine sandbodies, but it also shows trends sufficiently accurate for planning seismic surveys.

 

INTRODUCTION

 

Although geologic journals contain a wealth of data and ideas that are relevant to petroleum exploration and development, they commonly are not fully used.  In no small measure, this is because of the time required to search and retrieve the articles or elements of those articles that are most pertinent.  Digital versions of the journals, where available, can be used to reduce substantially the time that is required to obtain the needed information.

 

More specifically, valuable data are represented by AAPG publications on the Internet and CD-ROM. This digital library may be searched for any word, combination of words, or related words using Boolean operators. The searchable text is linked to page images, including figures, which of themselves are a vast data resource.

 

Figures in AAPG Publications are useful in more than one way. First, they are a basic element of information, commonly providing background, setting, or context. Second, some provide specific information, which with appropriate permission may be included in presentations or as part of the substantiating data package for prospects or areas of interest. Third, again with appropriate permission, information in the figures may be altered, edited, or enhanced, with speed, to form the basis for a synthesis of the data in order to develop a framework and delineate geologic features.

 

EXAMPLE: HACKBERRY SAND

 

During the study of sand in the lower part of the Frio Hackberry Shale in southeasternmost Texas and southwesternmost Lousiana, it became desirable to map the entire area of sand-bearing Hackberry. The specific objective in this part of the study was to prepare a regional isopach map of sand in the lower part of the Hackberry.

 

The Hackberry sandstone is considered to have been deposited in various parts of complex fans that formed in a deep-water embayment dominated by shale. In order to expedite preparation of the maps, the AAPG Digital Library (of AAPG Publications) was used to search and retrieve relevant articles. Because illustrations were to be utilized, it was anticipated that the term “Hackberry” should be accompanied by a connector in the search that would exclude abstracts. This was accomplished by the following search criteria: hackberry NOT abstract under the TITLE category (Figure 1).  The result of this search was the identification of 11 articles (Figure 2).

 

Each pertinent article was retrieved, and figure captions were read in order to determine which figures might be of value in preparation of an isopach map of the sandstone in the lower part of the Hackberry.

 

To view the images of the figures to be evaluated, the files that contain the particular page images (in PDF) are opened for viewing by selecting for each article the PDF icon accompanying the first page of the text.  Using CD-ROMs, the appropriate disks are selected and the search criteria are repeated to locate the desired article. For mapping of Hackberry sand, files for the following articles were opened: Cossey and Jacobs (1992), Eubanks (1987), and Paine (1968).

 

Cossey and Jacobs (1992) present an isopach map of Lower Hackberry Sand in southwesternmost Louisiana (Figure 3). A corresponding map for Jefferson County, Texas, is in the article by Eubanks (1987) (Figure 4). Paine (1968) contains a map of the Hackberry sand for the eastern part of the Hackberry embayment (Figure 5).

 

To use these images in an image-editing package, such as Canvas, which is the package used in this example, they must be received  in a format such as “tiff” or “bitmap”. The images can be “cut and pasted” directly from the provided pdf files into the selected image-editing package as a “bitmap” image.  From the Internet, the pdf file is opened and the image to be used is located.  The image can be copied by using the select graphics menu item under the tool menu, and the tool is dragged across the image to outline the area being considered. The image is enlarged to maintain resolution quality; “copy”, opening of the editing package, and “paste,” which follow, represent the subsequent requirements for conversion.  From the CD-ROMs, the images can be exported to the format HPGL (Hewlett Packard Graphics Language) and subsequently converted. Many different software packages are available for file conversion. By using the “file convert” command, within Hijaak, the selected files are converted into tiff and placed into a separate folder.

 

Direct scanning of the figures is another option of capturing images in image-editing acceptable formats. After scanning, the image may or may not need to be converted, depending on capabilities of the scanning hardware.  Scanning provides a somewhat more flexible method of obtaining the image; it provides greater flexibility and control of the images; and it may allow for enhancement of the contrast (and quality) of the image over what can be obtained from conversion of the digital version.

 

After conversion, the tiff images are imported into Canvas (in this example) for manipulation, by either the “Place” command or the “Open” command. Once the images are in Canvas, the “save as” command is used to convert the image to Canvas format. The files are easily manipulated in this format.

 

The images should be cropped or trimmed before enhancement is begun. The image can be cropped in Canvas, simply by selecting the item and using the control dots around the image.  The control dots are pulled inward to eliminate the excess.  Once information is cropped, it cannot be restored; caution is advised.

 

The cropped images can then be placed into a single file. When working with black and white images, it is convenient to convert the figures to different colors; e. g., black changed to blue or red. This process is accomplished by changing the “fore” color of the image, in Canvas, using the fore color box which is located in the central part of the toolbox. Color can be selected from a palette that is activated by clicking on the appropriate icon.

 

At this stage, a scale must be selected. In the Hackberry example, the images are also oriented to a common reference and positioned accordingly. The image from Cossey and Jacobs (1992) (Figure 3) is used as the base image. Maps from Eubanks (1987) and Paine (1968) (Figures 4 and 5, respectively) can then be imported using the (place) command.  To place a figure into the file, under the “file” menu item, one proceeds to place, selects the desired file name of the figure, and selects “OK”.  Images can be placed onto the same layer or on a unique layer. Images from the other two articles can be made transparent, scaled, and oriented with respect to the Cossey and Jacobs image (Figure 6). Figures with overlap need to be transparent to allow viewing of all figures at any given time. Creating transparent figures is accomplished by selecting the image and using the (copy) box located near the base of the toolbox. Clicking once on the (copy) box activates it; using the “or” option will allow underlying images to be seen and to retain their original colors.

 

The final step is enhancement or editing of the image. The data in the images were enhanced from information from selected well logs. The isopach map resulting from this compilation / synthesis (Figure 7) shows trends of deep-marine fan sands sufficiently accurate to outline 3-D seismic surveys.  Obviously, problems may occur where different vintage images are used; however, in most cases, data are sufficiently compatible to allow preparation of good generalized maps.

 

 

REFERENCES

 

COSSEY, STEPHEN P. J., and JACOBS, RICHARD E., 1992, Oligocene Hackberry Formation of Southwest Louisiana: Sequence Stratigraphy, Sedimentology, and Hydrocarbon Potential: AAPG Bulletin, Vol. 76, p. 589–606.

 

Eubanks, L. G., 1987, North Sabine Lake Field: Complex Deposition and Reservoir Morphology of Lower Hackberry (Oligocene), Southwest Louisiana: AAPG Bulletin, Vol. 71, p. 1162–1170.

 

Paine, William R., 1968, Stratigraphy and Sedimentation of Subsurface Hackberry Wedge and Associated Beds of Southwestern Louisiana: AAPG Bulletin, Vol. 52, p. 322–342.