Appendix A. Sample Use Case


This appendix is in support of the "Using QFD to Align Decision Making Horizontally Across a Company" section in Chapter 2, "Aligning Decision Making and Synchronizing Distributed Development Horizontally in the Organization." It provides a sample use case to illustrate the combined use of three disciplinesgeology, geophysics, and petrophysicsfor oil and gas exploration. This use case is provided as motivation to the central problem of the section, (i.e., selection of a developer's toolkit for shared earth modeling company-wide across all components of O&G's product suite).

While providing a tutorial on oil and gas exploration is out of the scope of this book (never mind that I'm not qualified to do so), some explanation on what the use case is actually doing will be provided after each use case step.[1]

[1] Thanks to John Fierstien and Gary Paisley for helping with the geoscience of this use case.

The name of this use case is Create 2D Cross Section. The goal is to gain a better understanding of where oil might be by producing a 2D display of a geologic cross section, augmented with measures made of wells (petrophysics) and data from seismic surveys (geophysics) for a line-of-section drawn on a basemap by an interpreter. Figure A.1 will be used as a visual reference in the use case. The steps for the use case follow:

1.

Log-in as an interpreter with valid ID and create new project or load existing project to be evaluated.

Explanation: Interpreters are geoscientists that interpret data to determine the location of oil and gas. A project is just a bundle of workmodels, data, notes, and so onthat gets saved. A given project may have a number of different interpreters, so logging-in not only prevents unwanted access to a project, but provides a way to keep separate the interpretations of one person from another.

2.

Set stratigraphic column to be used for the project.

Explanation: A stratigraphic column is a model of the sequence or layers of rock formations in an area. Different areas of the world have different geology: the strata that is exposed in Houston, Texas, is different from the strata that is exposed in Denver, Colorado. The interpreter is simply specifying the geology to be used for the project.

3.

Review available well data and select wells of interest.

Explanation: Wells are oil wells; actually wells drilled in exploration of oil: many are "dry holes." Wellseven dry holesare important because they provide one of the few opportunities to get a direct "look" inside the earth, called well logging. If an interpreter looks at half a dozen wells in a field, and all had oil bearing rock at the same depth in the hole, the interpreter might make the leap of faith that oil bearing rock lies at that same depth in other parts of the field.

4.

Select well log template or create new template with well template editor, then preview with well viewer.

Explanation: A well log is a report of the data obtained from logging a well. An interpreter uses a log template as a starting place to specify what properties are to be displayed on the well log, such as electrical resistivity. Because oil is an insulator, it "resists" electricity. By viewing a well log of the electrical resistivity measured up and down the borehole, the interpreter can spot depths where there may be oil.

5.

Review available 3D seismic surveys of the area and select one of interest.

Explanation: Whereas the geologic model of an area is based on observations of strata at the surface and what we know about geology of the earth in general, and whereas well logs are based on measures made at particular spots along the borehole of particular wells, seismic surveys are a way to remotely view inside the earth on a broader scale giving a fuller picture of the earth for the area of interest. 3D seismic surveys allow the geoscientist to select an arbitrary section through the seismic data that matches any cross section (explained in step 7) that a geoscientist might construct.

6.

Create basemap showing well locations.

Explanation: A basemap is basically what most of us think of when we think "map": a view of the earth's surface from above. Of particular interest on the basemap are the locations of wells that have been drilled in the area. See basemap (center) in Figure A.1. Wells selected from step 3 are shown on the basemap.

7.

Draw a line-of-section on basemap that includes wells to evaluate; View 2D cross section.

Explanation: A line-of-section is a straight line, or series of connected straight lines, on a basemap. An interpreter usually draws a line-of-section connecting several wells in an area, as has been done in Figure A.1; see the dark line running northwest to southeast on left of basemap. The line-of-section specifies that part of an area for which the interpreter wants to view the cross section. A cross section is a view of the earth from the side. When you drive your car through a hill where the hill has been cut-away for the road, you are looking at a cross section of the hill. Having included wells in the line-of-section, the interpreter will get a view of not only the geologic strata that corresponds to the line-of-section but also a well log superimposed over each borehole in the cross section. The interpreter will also get a cross section of the seismic data along the line-of-section. In this way, the interpreter combines information from three disciplinesgeology, petrophysics, and geophysicsto form a more complete idea of what actually lies beneath the earth and where oil and gas are likely to have been created and trapped in a reservoir.

Figure A.1. Basemap (center) with line-of-section (LOS)the dark line running northwest to southeast on left of basemapindicating that area for which the geoscientist wants a geologic cross section, well logs, and seismic survey displayed in 2D.




Succeeding with Use Cases. Working Smart to Deliver Quality
Succeeding with Use Cases: Working Smart to Deliver Quality
ISBN: 0321316436
EAN: 2147483647
Year: 2004
Pages: 109

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