Changes

==Procedure==

==Procedure==

Follow the steps listed in the table below to perform a sequence analysis of a seismic section (adapted from Vail<ref name=ch21r44 />).

Follow the steps listed below to perform a sequence analysis of a seismic section (adapted from Vail<ref name=ch21r44 />).

# Look for places where two [http://wiki.seg.org/wiki/Dictionary:Reflector reflectors] converge. Where reflectors converge, there will be terminations.

# Mark the [http://wiki.seg.org/wiki/Dictionary:Reflection reflection] terminations with arrows.

# Draw in the discontinuity surface between the [http://www.glossary.oilfield.slb.com/en/Terms.aspx?LookIn=term%20name&filter=onlap onlapping] and [http://www.glossary.oilfield.slb.com/en/Terms/d/downlap.aspx downlapping] reflections above, and the truncating and [http://homepage.ufp.pt/biblioteca/Seismic/Pages/Page22.htm toplapping] reflectors above. If the discontinuity surface becomes conformable, trace its position across the section by reflection correlation.

# Continue the process described in steps 1, 2, and 3 for all the seismic lines in the grid.

| 1 || Look for places where two [http://wiki.seg.org/wiki/Dictionary:Reflector reflectors] converge. Where reflectors converge, there will be terminations.

# Close all seismic grid loops by checking the loop ties for each discontinuity or its correlative equivalent.

# Categorize each discontinuity.

| 2 || Mark the [http://wiki.seg.org/wiki/Dictionary:Reflection reflection] terminations with arrows.

#* '''If''' it is characterized by regional onlap above and truncation below '''then''' it is probably a [[Definitions_of_depositional_system_elements#Sequence_boundaries|sequence boundary]]

#* '''If''' it is characterized by regional downlap '''then''' it is most likely a downlap surface

| 3 || Draw in the discontinuity surface between the [http://www.glossary.oilfield.slb.com/en/Terms.aspx?LookIn=term%20name&filter=onlap onlapping] and [http://www.glossary.oilfield.slb.com/en/Terms/d/downlap.aspx downlapping] reflections above, and the truncating and [http://homepage.ufp.pt/biblioteca/Seismic/Pages/Page22.htm toplapping] reflectors above. If the discontinuity surface becomes conformable, trace its position across the section by reflection correlation.

| 4 || Continue the process described in steps 1, 2, and 3 for all the seismic lines in the grid.

| 5 || Close all seismic grid loops by checking the loop ties for each discontinuity or its correlative equivalent.

| 6 || Categorize each discontinuity.

* '''If''' it is characterized by regional onlap above and truncation below '''then''' it is probably a [[Definitions_of_depositional_system_elements#Sequence_boundaries|sequence boundary]]

* '''If''' it is characterized by regional downlap '''then''' it is most likely a downlap surface

==Marking a seismic section, marking==

==Marking a seismic section, marking==