2. SEDPAK BASICS
2.01 Functions and Variables
2.02 The Architecture of SEDPAK
2.03 The SEDPAK Graphical User Interface
2.04 Accelerators and Mnemonics
2.05 SEDPAK LAUNCH and Other Menus and the SEDPAK Window
2.06 The File Menu
2.07 Sedpak Files
2.08 The Option Menu Command
2.09 The Balloon Help and Help Menu.
2.10 The Plotter
2.11 The Data Sheet
2.12 The Calculator
2.13 Warning Dialogs
2.14 User Inputs versus Default Values in SEDPAK
2.15 Non-Interactive Execution of SEDPAK
2.16 Overlay
2.17 Adobe
In order to interpret and use the results of the SEDPAK simulation, a clear understanding is required concerning the nature of the inputs and outputs to the program. Towards this end, there is a short discussion of the role each plays in the SEDPAK software. The terminology defined in this section will be used throughout the manual, so take a moment to become familiar with them now.
Constructing a SEDPAK model is an iterative process. The output from a simulation model is 'observed', the input 'refined', and the model 'executed' again. This process is repeated until the desired and observed sedimentary geometries of the basin are in agreement. This process of repeatedly running the simulation is the key to determining the most appropriate input values, even when using carefully defined datasets determined from seismic, well data and/or outcrop. This iterative approach often leads to the re-examination of the original datasets, and a recognition when their interpretation may not be accurate.
Simulation parameters used in SEDPAK are distinguished as:
A control variable is used by SEDPAK to limit or redirect some aspect of the computations
and has no dimensions. For example, the number of time steps over which
the simulation is to be executed.
A process variable represents some physical basin characteristic which has dimensions. For example, the rate of pelagic carbonate deposited in meters/thousand years within some basin column during a particular time step.
A preset variable is an independent parameter that has been assigned a fixed value, or range of values within SEDPAK. For example, the number "Pi" is set to 3.1416. Preset values may represent either process or control parameters. Preset process variables reflect the assumptions made regarding geological processes modeled by SEDPAK, whereas preset control variables usually reflect limitations imposed on the software by its computer host environment. Preset variables cannot be changed in the SEDPAK inputs. However, it is important to know the actual values used, because they impose limitations and constraints on the program which should be taken into account when interpreting SEDPAK output. Preset variables and their values are described throughout this manual. Those who wish to change preset parameters should contact the University of South Carolina Stratigraphic Modeling Group (see front page).
A user-specified variable is an independent variable which takes a value, or range of values, as input during initialization. Like preset variables, user-specified parameters can be process or control variables. Because the results of a simulation run are explicitly dependent on user-specified inputs, SEDPAK users should become familiar with the meaning of each such value, and how each one constrains or alters the program output.
The SEDPAK editor assigns a default value to each user-specified variable. In almost every case this value is zero, and has little relationship to the actual value needed by the SEDPAK program. The recommended technique for creating a new file is to modify a file which has values similar to those desired for the new file. The new file would, of course, inherit the values of the user-specified variables from the old file in the benchmarks directory.
A numeric variable is associated with a function whose domain and range are sets of real numbers. For example, the porosity (ø) in sand as a function of depth (d) in feet below the earth's surface is calculated as ø(d) = 5670/(21000+d). Here (ø) is the function, (d) is an independent numerical variable whose domain of possible values is (roughly) the real interval [0 to 20,519,716]; and ø(d) is a dependent numeric variable whose range of possible values is (roughly) the real interval [0.000027 to 0.27]. Note that numeric variables and their values can be independent or dependent, process or control, and/or default or user-specified. An integer variable is a special case of a numeric variable, wherein each value in the domain and range is integral, such as -2, -1, 0, 1, etc.
A logical variable is associated with a function whose domain and range are linguistic terms. For example, the clastic source direction(s) that SEDPAK uses for deposition are "neither side", from "the left", from "the right", from "both sides". Logical variables can be independent or dependent, process or control, and/or default or user-specified.
2.02 The Architecture of SEDPAK
Chapters 3, 4, and 5 of this manual describe interactive editing and execution
of SEDPAK. The program executes the sequence of steps described in Table
2.2.1 and Figure 2.2.1 for as many time steps as specified. Parameters used
by the program have been grouped logically and are accessed by category.
Names of the categories and the section of this manual corresponding to
the category are shown in Table 2.2.2.
READ DATA FILE
ALLOCATE SYSTEM RESOURCES
INITIALIZE
LOOP FOR EACH TIME STEP
DETERMINE CLASTICS AVAILABLE
SET SEA LEVEL
APPLY TECTONIC ADJUSTMENT
LOCATE SHORELINE
ERODE ALLUVIUM
DEPOSIT CLASTIC SEDIMENT
DEPOSIT CARBONATES
DEPOSIT PELAGIC CARBONATES
COMPACT SEDIMENTS
PERFORM SEDIMENT LOADING ADJUSTMENT
WINNOW SHALES
APPLY DEUS EX MACHINA SURFACE ADJUSTMENTS
DEPOSIT SEDIMENT FROM OUT OF PLANE
CALCULATE MATURATION
PLOT GEOMETRIES
END LOOP
PERFORM FINAL COMPACTION
PLOT FINAL GEOMETRIES
Table 2.2.1. Flow diagram for SEDPAK.
The SEDPAK simulation model is initiated by determining the most reasonable initial shape for the basin and its subsidence history. Subsidence is determined by tracking the behavior of the lowest surface of interest in the basin through time. These varying subsidence or uplift rates are then input for specific locations and times. The gross sedimentary geometries from seismic and/or cross sections are visually matched with simulation outputs by iteratively modifying such parameters as rate of sediment input, distance of sediment transport into the basin, position of wave base, and position (or offset) of the sea level curve with respect to the basin surface.
SEDPAK uses forward modeling techniques and operates in equally spaced time steps on a two-dimensional cross section divided into columns of equal widths. The user enters the initial and time varying parameters. The values of these parameters are important to the quality of the simulation and care needs to be taken in choosing them. SEDPAK reads the parameters and generates sedimentary geometries according to depositional and erosional rules.
Figure 2.2.1. Flow diagram for SEDPAK.
As illustrated in Figure 2.2.1, within each time step, a fixed sequence of operations creates or modifies the sedimentary geometries. First, tectonic adjustments change the accommodation at points defined by the user across the basin. Next, the intersection of the sea level position with the basin surface defines a bayline location (Posamentier and Vail, 1988) marking the base of the alluvial plain. Sediment eroded landward from the bayline location is added to the sediment supply. Seaward of the bayline, sediment erodes or is deposited according to geometrical rules. After clastic deposition is completed, carbonates accumulate in-situ to form reefs. From the reef positions, excess carbonate is transported downslope as talus or turbidite, or backslope as lagoonal sediment. Next, a pelagic drape, specified as a rate, blankets the submarine setting. Sediment loading and compaction adjustments, followed by winnowing of shales, and out-of-plane erosion and deposition complete the operations for the time step. These operations are summarized by the 16 steps are described below and represented diagramatically in the Figure 2.2.1.
0. Define initial conditions (Figure 3.3.1)
- Start and Stop time
- Start and end location
- Number of Time Steps and Columns
- Basin Surface topography (Figure 3.4.1)
- Sea Level Offset
- Angles of Erosion and Deposition (Figure 3.10.2)
1. Depositional triangles determined by SEDPAK from:
- Time/rate pairs (Clastic Supply) (Figure 3.8.1)
- Time/distance pairs (Depositional Distance) (Figure 3.8.2)
2. Set Sea Level
- Time/depth pairs (Figure 3.5.2)
- Mathematically computed curves (Figure 3.5.4)
3. Set Subsidence
- Time/rate pairs at specified locations (Figure 3.6.1)
4. Locate shoreline (Figure 3.8.3)
- Locate bayline/intersection of sea level with basin margin
5. Perform alluvial erosion (Figure 3.8.3)
- Erosion landward of bayline
- Sediment added to depositional triangle
6. Deposit alluvial and marine clastics
- Deposit sediment in columns to sea level on coastal shelf (Figure 3.8.4)
- Simultaneously fill columns of alluvial plain
- Sediment wedge is deposited from shore break to deeper water
- Sedimentation controlled by angles of deposition and repose (erosion)
(Figure 3.8.3).
7. Deposit carbonates
- In-situ, dependent on water depth (Figure 3.11.1); accumulation can reach 90š,
accumulates in intermediate time steps of 1000 years.
- Lagoonal Damping (Figure 3.13.1)
- Talus/turbidite from shelf break into basin and/or lagoon - depends on
prescribed distances and depositional angles (Figure 3.16.2)
- Clastic suppression of carbonates
8. Pelagic Deposition (Figure 3.15.1)
- Uniform over basin
- Time varying
9. Perform Compaction (Figure 3.17.1)
- Function of porosity and lithology
- Baldwin-Butler North Sea equations
10. Sediment loading (Figure 3.17.1)
- Isostatic response
- Crustal rigidity
11. Winnow Shales (Figure 3.9.1)
- Depth/rate pairs
- Position dependent
- Effective down to wave base
- Direction set opposite to direction of sedimentation
12. Deus ex machina (Figure 3.6.2)
- Erosional surface drawn by geologists
- Time dependent
- Sediment removed is lost from system
13. Out of plane deposition (Figure 3.20.1)
- Used to account for sedimentation from out of plane
- Location and thickness of lithology specified
- Time dependent
14. Determine thermal history (Figures 3.21.1, 3.22.1, and 3.23.1)
- From thermal gradient and surface temperature
- TTI or kinetic model
- Calculate potential for maturation if source rock present
15 Plot
SECTION PARAMETERS 3.1 Comments 3.2 Constants 3.3 Setup 3.4 Basin Surface 3.5 Sea Level 3.6 Subsidence 3.7 Clastic Supply 3.8 Depositional Distance 3.9 Winnowing 3.10 Depositional Parameters 3.11 Carbonate Rates 3.12 Hardgrounds 3.13 Lagoonal Damping 3.14 Wave Damping 3.15 Pelagic Deposition 3.16 Carbonate Parameters 3.17 Overburden 3.18 Time Boundaries 3.19 Pseudo Wells 3.20 Out of Plane Deposition 3.21 Thermal Gradients 3.22 Surface Temperatures 3.23 Maturation Parameters
Table 2.2.2. Input parameters.
2.03 The SEDPAK Graphical User Interface
The graphical user interface (GUI) of SEDPAK has been built upon Motif,
from the Open Software Foundation. It is quite similar to other GUIs, e.
g., Windows, or work place shell. Several of the terms used in this manual
to define operations for the SEDPAK GUI are defined here. SEDPAK uses only
the left button on the mouse. This may not be true for the window manager
for your system or for other applications which may run on your system.
abandon Abandon changes not yet applied to plotter and/or data sheet.
accelerator A key or keyboard combination that activates menu items without posting a menu. Accelerators are useful for accessing frequently used commands, independent of the mouse.
apply Applies changes and up dates the associated plotter and data sheet.
cancel Causes the plotter and/or data sheet to close without activating any changes not yet applied.
click To press and release a mouse button.
cursor The vertical bar (|) which appears in text. The cursor indicates the position at which characters typed at the keyboard will appear in the text.
dialog A dialog is a window invoked by the application for the purpose of grouping components that are secondary to the main tasks of the application.
double-click To press and release a mouse button twice in rapid succession.
drag To press and hold a mouse button while moving the mouse.
icon A graphical image which activates an application.
menu A list of currently available selections.
menu bar A rectangular area at the top of a window which displays the titles of pull-down menus.
mouse A pointing device typically used along with a keyboard for applications using a GUI.
mnemonic A single character, indicated within a menu label by an underline, which provides a quick way to activate a menu item on a posted menu.
ok Applies any changes and upgrades associated plotter and data sheet (same as Apply) and then closes plotter and/or data sheet.
open To begin working with a text or data file or to start an application program.
pointer The graphical image which appears in a window to indicate the current position of the mouse.
pull-down menu A menu pulled down from the application's title bar.
scroll area An area of a window which contains text or a list. The contents can made to move up or down (or left or right) in order that all of the contents may be viewed.
scroll bar A graphical device used to change the viewable section of a list or data file. The scroll bar has a slider, scroll area, and scroll arrows. The view is changed either by pressing on one of the scroll arrows or by moving the slider within the scroll area. The position of the slider in the scroll area indicates the position of the section of the list or data file being viewed.
select To choose an action to be performed or an object to be acted upon by double clicking or dragging (see above). Selected text will acquire a dark background, and will be deleted when new words or numbers are typed in the same window.
select button The mouse button used to make a selection (for SEDPAK it's the left button).
tear-off A pull-down menu that can be torn off and displayed independently.
window A rectangular subset of the display screen.
2.04 Accelerators and Mnemonics
The user may wish to access menu items using the keyboard, rather than
the mouse, and take advantage of accelerators and mnemonics. The accelerators are available from the pull-down menus on the SEDPAK EXEC and SEDPAK EDIT
menu bars and are invoked by a control key stroke and a keyboard character
(upper or lower case). For example, Ctrl + o implies the user should press
the "Control" key and "o" at the same time, to open a file for execution
or editing. The mnemonics are indicated by an underlined character on the SEDPAK EXEC and the SEDPAK
EDIT menus, as well as on all the plotters associated with the EDIT panel.
They are executed by pressing that character (upper or lower case) and the
"Alt" key at the same time. The location of the "Alt" key varies for different
machines and keyboards and it may be necessary to experiment with the keyboard.
The mnemonics used in SEDPAK are listed below. When the mouse pointer is on the SEDPAK EXEC menu, the following mnemonics may be invoked.
Alt + f The pull-down menu under File is activated.
Alt + o The Initialization File Interface dialog (from Option) is activated.
Alt + h The Help file is activated.
When the mouse pointer is on the SEDPAK EDIT menu, the following mnemonics may be invoked.
Alt + f The pull-down menu under File is activated.
Alt + o The Initialization File Interface dialog is activated.
Alt + h The Help file is activated.
Alt + e The Comments dialog will be activated.
Alt + n The Constants dialog will be activated.
Alt + s The Setup dialog will be activated.
Alt + b The Basin Surface plotter will be activated.
Alt + l The Sea Level cascade menu will be activated.
Alt + u The Subsidence plotter will be activated.
Alt + y The Clastic Supply cascade menu will be activated.
Alt + t The Depositional Distance cascade menu will be activated.
Alt + w The Winnowing cascade menu will be activated.
Alt + d The Depositional Parameters dialog will be activated.
Alt + c The Carbonate Rates plotter will be activated.
Alt + r The Hardgrounds plotter will be activated.
Alt + g The Lagoonal Damping plotter will be activated.
Alt + v The Wave Damping cascade menu will be activated.
Alt + p The Pelagic Deposition plotter will be activated.
Alt + m The Carbonate Parameters dialog will be activated.
Alt + a The Time Boundaries data sheet will be activated.
If the mouse is located on one of the EDIT panel parameter pull-down menus such as Sea Level, Subsidence, Clastic Supply, Deposition Distance, Winnowing or Wave Damping, mnemonics are indicated as before by an unlined character and activated by pressing that character and the Alt key. If the mouse is on one of the plotters invoked from the SEDPAK EDIT panel, the following mnemonics may be used.
Alt + c Activates the Curves pull-down menu.
Alt + p Activates the Points pull-down menu.
Alt + o Activates the Option pull-down menu.
Alt + r Activates the Printer pull-down menu.
Once a pull-down menu appears, the mnemonics are listed on the menu labels by a single underlined character. A mnemonic can invoke a variety of actions. For instance, under the File menu on the SEDPAK EXEC panel the following mnemonics are available:
o Open a file for execution.
p Pause the execution of SEDPAK.
r Resume the execution of SEDPAK.
l Load then Restart the execution of SEDPAK.
s Activates the Print Selection pull-down menu.
c Close Simulation of SEDPAK and close the active simulation window.
q Quit SEDPAK execution and the SEDPAK EXEC menu is removed.
If the mouse arrow is placed on the SEDPAK EXEC menu, the following accelerators may be used:
Ctrl + o Open a file for execution.
Ctrl + p Pause the execution of SEDPAK.
Ctrl + r Resume the execution of SEDPAK.
Ctrl + l Load then Restart the execution of SEDPAK.
Ctrl + s Activates the Surface Snapshot file dialog
Ctrl + c Close Simulation of SEDPAK and close the active simulation window.
Ctrl + q Quit SEDPAK execution and the SEDPAK EXEC menu is removed.
If the mouse arrow is placed on the SEDPAK EDIT menu, the following accelerators may be used:
Ctrl + o Open a file for editing.
Ctrl + c Close the file being edited.
Ctrl + s Save the file being edited.
Ctrl + a Save as - save the current file being edited as a new file.
Ctrl + q Quit SEDPAK EDIT menu and remove it.