Changes

Files with optional ''x''–''y'' information contain cultural or specialty information. Cultural information, that is, lease or topographic data, is considered map enhancement not critical to a project. Cultural information allows technical information and subsurface interpretations to be related to natural or man-made surface features. These files are at times used to highlight certain information to augment map displays. Examples of customized files might include man-made features (towns, roads, pipe lines, and leases), geomorphic data (waterways and topographic relief), highlighted wells (horizon penetrations, exploratory wells, and platform locations), or contour data (gravity, [[magnetics]], and bathymetry).

Files with optional ''x''–''y'' information contain cultural or specialty information. Cultural information, that is, lease or topographic data, is considered map enhancement not critical to a project. Cultural information allows technical information and subsurface interpretations to be related to natural or man-made surface features. These files are at times used to highlight certain information to augment map displays. Examples of customized files might include man-made features (towns, roads, pipe lines, and leases), geomorphic data (waterways and topographic relief), highlighted wells (horizon penetrations, exploratory wells, and platform locations), or contour data (gravity, [[magnetics]], and bathymetry).

===Seismic preparation===

===Seismic preparation===

Displaying various vintages of data with the same datum, polarity, phase, and scaling is a convenience afforded by the workstation (Figure 2).

Displaying various vintages of data with the same datum, polarity, phase, and scaling is a convenience afforded by the workstation ([[:file:two-dimensional-geophysical-workstation-interpretation-generic-problems-and-solutions_fig2.png|Figure 2]]).

 

[[file:two-dimensional-geophysical-workstation-interpretation-generic-problems-and-solutions_fig2.png|thumb|{{figure number|2}}Seismic preparation.]]

Correcting for datum shifts between vintages of seismic data is a tedious chore on paper. In the electronic environment, these shifts are assigned to each seismic line and the data adjusted at the time of display. After loading relative to the ''x''–''y'' location, data are adjusted to a common reference plane. Some data require a bulk time shift to tie other data sets. Bulk shifts are executed primarily in two ways: a correction time is added or subtracted to each profile and a correction velocity is applied to the profile. During interpretation, corrections dealing with a horizon are linked to that horizon, thus allowing for time variant adjustments. These conveniences allow the explorationist to concentrate on interpretation and decision making and not on data management<ref name=pt08r22>Valusek, J. E., Chan, A. W., 1989, 2-D seismic workstations—tools or toys?: Asian Oil & Gas, Jan. 1989.</ref>.

Correcting for datum shifts between vintages of seismic data is a tedious chore on paper. In the electronic environment, these shifts are assigned to each seismic line and the data adjusted at the time of display. After loading relative to the ''x''–''y'' location, data are adjusted to a common reference plane. Some data require a bulk time shift to tie other data sets. Bulk shifts are executed primarily in two ways: a correction time is added or subtracted to each profile and a correction velocity is applied to the profile. During interpretation, corrections dealing with a horizon are linked to that horizon, thus allowing for time variant adjustments. These conveniences allow the explorationist to concentrate on interpretation and decision making and not on data management<ref name=pt08r22>Valusek, J. E., Chan, A. W., 1989, 2-D seismic workstations—tools or toys?: Asian Oil & Gas, Jan. 1989.</ref>.

The electronic environment provides the interpreter with a greater degree of detail than does paper. This detail is quantified by the size “word” written to tape and used for transfer of data. Typically, processed data are written as 16-or 32-bit words. This density of information translates to large volumes of information and requires a great deal of storage space. Retrieval and display time are slowed, even with the latest hardware. To minimize the display time and reduce storage space, data are reformatted during loading to an 8-bit word size for structural and stratigraphic interpretations. Once interpretation is complete, the 32-bit data can be loaded for detailed computations and attribute analysis.

The electronic environment provides the interpreter with a greater degree of detail than does paper. This detail is quantified by the size “word” written to tape and used for transfer of data. Typically, processed data are written as 16-or 32-bit words. This density of information translates to large volumes of information and requires a great deal of storage space. Retrieval and display time are slowed, even with the latest hardware. To minimize the display time and reduce storage space, data are reformatted during loading to an 8-bit word size for structural and stratigraphic interpretations. Once interpretation is complete, the 32-bit data can be loaded for detailed computations and attribute analysis.

===Geological preparation===

===Geological preparation===

Well information is used in a variety of ways. The most basic is incorporation of geological tops into the [[seismic interpretation]] (Figure 3). These tops are input digitally or via keyboard entry. Once in the database, this information is easily manipulated and can be used for modeling.

Well information is used in a variety of ways. The most basic is incorporation of geological tops into the [[seismic interpretation]] ([[:file:two-dimensional-geophysical-workstation-interpretation-generic-problems-and-solutions_fig3.png|Figure 3]]). These tops are input digitally or via keyboard entry. Once in the database, this information is easily manipulated and can be used for modeling.

 

Models generated from log data aid the seismic interpreter in relating seismic reflections to lithological information. Well tops associated with horizons on the seismic profiles fully integrate an exploration concept. Lithology types from the log model can be superimposed on the seismic traces for display or modification. By integrating a sonic log and density log (if available), one-dimensional seismograms that are created can help to identify seismic reflections representing geological interfaces. Log models can also be converted to 2-D synthetic seismic models by integrating velocity information and convolving the model with a seismic wavelet. Models can imitate seismic response to test geological concepts. Seismic resolution of geological features are determined, and simulated profiles are generated to tie wells.

Models generated from log data aid the seismic interpreter in relating seismic reflections to lithological information. Well tops associated with horizons on the seismic profiles fully integrate an exploration concept. Lithology types from the log model can be superimposed on the seismic traces for display or modification. By integrating a sonic log and density log (if available), one-dimensional seismograms that are created can help to identify seismic reflections representing geological interfaces. Log models can also be converted to 2-D synthetic seismic models by integrating velocity information and convolving the model with a seismic wavelet. Models can imitate seismic response to test geological concepts. Seismic resolution of geological features are determined, and simulated profiles are generated to tie wells.

Velocity information is important in relating geological data to seismic data. This information is derived by the interpreter from a variety of sources, the most common being check shot surveys obtained from wells, time-depth charts derived from stacked seismic data or seismic to well correlation, and velocity function curves. These data are input in digital form via digitizer pad or keyboard entry (Figure 3). When concatenated to a well, the wellbore, log curves, and geological tops can be displayed with the seismic. A three-dimensional velocity field can be created for conversion of time surfaces to depth maps.

Velocity information is important in relating geological data to seismic data. This information is derived by the interpreter from a variety of sources, the most common being check shot surveys obtained from wells, time-depth charts derived from stacked seismic data or seismic to well correlation, and velocity function curves. These data are input in digital form via digitizer pad or keyboard entry ([[:file:two-dimensional-geophysical-workstation-interpretation-generic-problems-and-solutions_fig3.png|Figure 3]]). When concatenated to a well, the wellbore, log curves, and geological tops can be displayed with the seismic. A three-dimensional velocity field can be created for conversion of time surfaces to depth maps.

With a time-depth relationship established, the [[synthetic seismograms]] are then adjusted to tie the seismic to the well control. Velocity data are used to adjust synthetic curves, seismic and well log models, depth converted horizons, and interval maps.

With a time-depth relationship established, the [[synthetic seismograms]] are then adjusted to tie the seismic to the well control. Velocity data are used to adjust synthetic curves, seismic and well log models, depth converted horizons, and interval maps.