January 16, 2003:

Interpretation Backup:

To backup your interpretation to disk, copy the folder C:\Documents and Settings\

All Users\Application Data\GeoGraphix\Sample Files\Projects\YourName \

InterpretationName and its contents (generally 20-60 files and folders).

Channel Amplitude Interpretation:

(Open a 2D Seismic Line). (on MHD-101). Scroll down to 0.860 seconds and SP 182.

Study amplitude of the peak and adjacent troughs. This appears to be a channel, and we

would like to interpret its location. Lets assume for now that the peak represents the top

of the channel. We want to pick only the peak representing the channel and nothing more.

PDW Horizons >Horizon Manager >(Add). ->Channel1 in Horizon name. ->Ch1 in

Symbol. (OK).

Click on color dot of Temp1. Pick a yellow color. (Close).

+Ch1 in the Horizons window and click on the seismic channel peak. Auto picking

interprets across the entire line. We only want the channel. Move the cursor along

the seismic channel and note the amplitude at the bottom of the window. The

channel appears to dim at amplitudes less than about 1000.

RightClick on the horizon >Pick Parameters >*Amplitude Test. ->1500 in Absolute

Threshold. (OK).

PDW Edit >Undo 2D Auto Pick. Pick the channel peak again. Note extent of

interpretation. Change threshold to 900 and pick again. No need to Undo previous

pick if you are lowering the threshold.

This technique is especially useful on 3D data. Practice on this channel and another

possible channel at SP 109 @0.875 seconds during the next interpretation

break.

Check other lines for the same channels.

Flattening:

Open line MHD-101. RightClick > Adjust Seismic Section > Scale Settings -> 10 tr/cm,

-> 15 cm/s. (OK). Look for stratigraphic changes. Nothing really jumps out.

We will use horizon flattening to bring out some subtle details.

+Temp1 in Horizons window. Click on the peak at 0.380 near the middle of the line.

Move cursor to seismic data. RightClick >Adjust Seismic Display >

Flatten to horizon: +Temp1. (OK).

Now look for stratigraphy. Note south [left] dipping progrades between 0.410 and 0.510

seconds. Note downlap pinchouts onto trough at 0.510 seconds.

This technique is very powerful, and very easy to do on computer workstations. Create

horizons F1-F3, and F5-F8. You already have F4 from last week’s class. Practice

stepping down one depositional package at a time looking for underlying

depositional structures and stratigraphy during the next interpretation break.

Hint: Each successive flattening horizon should be close to the first undulating seismic

reflector below your currently flattened horizon.

Fault Interpretation:

Open and Maximize LBT-201

Zoom to fault at SP 180-200. A scale of 10 tr/cm and 15 cm/sec is good for this.

PDW Faults > Fault Manager > (Add…) -> Fault1, -> Fault1 as symbol (OK). (Close).

(Fault1) in Faults window

(Segment Pick Mode) in Faults window

Identify a good break at the top [beginning of diffraction SP 182 @ 0.446 sec], a good break

near the bottom reflector [beginning of diffraction SP 192@ 1.157 sec], and select a

smooth concave-upward track for the fault.

Beginning at the top, LeftClick, move, LeftClick, move, LeftClick, move, DoubleClick to

terminate fault

There is no Undo button for faults.

To move fault, (Point Select Mode) in the Faults window, LeftClick fault point and drag

To add points, (Point Add Mode), LeftClick new point on existing fault and drag

To delete points, RightClick on a fault point, +Delete Point to remove

Repeat several times for practice.

Normal faults are concave upward unless proven otherwise.

(F4) in Horizons window.

(Zoom) to the F4 fault/horizon crossing, edit F4 horizon against fault using

(Drag picking mode) and the None pick parameter.

Make a continuous interpretation along fault from upthrown to downthrown contact.

You may have to try many times to move horizon into place. The software is not very robust.

Some of us might say it is full of bugs. Programmers prefer to call them features.

Fault Polygons:

In the Faults window (Fault Heave Pick Mode). On fault, LeftClick at the top contact, move to

bottom contact and click again.

Look on basemap for fault heaves.

Open line MHD-101

Make up imaginary left dipping normal fault on far-left side of line. Zoom to F4

fault/horizon crossing.

You should see 2 fault lines. The dark one is the one you just created. The light one is the

computer’s projection.

Do not edit the F4 horizon, but (Fault Heave Pick Mode) and draw an imaginary offset

on the fault.

Examine base map and the resulting fault polygon.

Open Line MHD-102 and note fault projection. This is useful on closely spaced seismic lines

when interpreting fault planes.

Return to Line MHD-101 and erase the imaginary fault. RightClick on fault >Delete Segment.

Edit horizon offsets against Fault1 during the next interpretation break. Remember to

include Fault Heaves for each horizon.

 

Interpretation Break: 40 Minutes

Experiment with Channel Interpretation, Flattening, and Faults

 

Load Well Logs to Project:

PDW Wells > Add Wells and Formations… > (Next >). Select all formations using (>>).

(Finish). Note three well locations now on basemap.

Annotate Wells on Base Map:

(Zoom) to wells. Need annotation. PDW Interpretation > Settings… > Well Display >

Horizontal Views. Line 1: +Operator Name. Line 2: +Well ID. Well Bore Display

Mode: +Show entire well bore. (OK).

PDW Map > Active Map Display Properties > Wells. Line 1: +Operator Name. Line 2:

+Well ID.

(OK).

Annotate Wells and Display Logs on Seismic:

PDW Interpretation > Settings… > Well Display > Vertical Views. Line 1: +Operator

Name. Line 2: +Well ID. Well Bore Display Mode: +Show entire well bore.

(OK).

Open seismic Line MHD-101. Note well 00-03 location. We are missing the well bore

and well logs. The project has no velocity information to calculate what time to use

for the depth values of the well logs. To load velocity information, click on the

(WellBase) icon which looks like a star on the right hand side of the window. [10th

icon from the top].

Near the top of the window, Well ID says 00-01. We want 00-03, so in the toolbar at the

top, look for the right arrow and click until you see Well ID:00-03.

About 1/4 down from the top, there is a line of pull down windows beginning with

Header. Select Velocity. Survey ID: ->1. Survey Type: ->checkshot. Ref.

Elevation: -> 493.4.

Shot Number ->1. Two-way time ->512.6. Measured Depth ->627.5.

Vertical Depth ->627.5.

Next line: Shot Number ->2. Two-way time ->1090. Measured Depth ->1790.6.

Vertical Depth ->1790.6.

PDW File >Exit.

(Update Well Data). (Update Well Logs).

PDW Wells > +Well ID 00-03. Component: Velocity/Synthetics Surveys. Survey: +1.

(Activate). Close window.

Select Display Curves one well at a time! Each well has different logs, and they

are not coded similarly.

On Line MHD-102, LeftClick 00-01 well dot. It will double in size. RightClick >

Well Log Display… >Left Curve Display. Curve Name: +DT.

Line Thickness: ->7. Color: +Pink. >Right. Curve Name: +IRDP.

Line Thickness: ->7. Color: +Pink. (OK).

On Line MHD-101, LeftClick 00-03 well dot. It will double in size. RightClick >

Well Log Display… >Left Curve Display. Curve Name: +DT.

Line Thickness: ->7. Color: +Pink. >Right. Curve Name: +IRDP.

Line Thickness: ->7. Color: +Pink. (OK).

There are no well logs for well 00-02.

It is customary to place SP or Gamma Ray curve on left and Resistivity curve on right.

For seismic correlation, DT [sonic] on one side and the synthetic on the other.

Log Codes:

SP: SPOT

Gamma Ray: GAM, DFGR

Resistivity: IMRD, IRDP, FOCR, SFSL, ILD

Density: RHOB, CNL, CNLL, FDCC

Sonic: DT

Post Well Tops:

Scroll down the seismic and look for Well Tops [formation names] next to the wells.

They are very faint.

To make them more obvious, PDW Wells >Default Formation Annotation.

Formation Annotation Marker: *Formation Tag, and select a fill color such as

Yellow. (OK).

(OK).

You will also notice that the WAB GRP top is far from the Wab horizon we interpreted

last week. We need to tie the well logs to the seismic. We do this with synthetic

seismograms or synthetics. We use the sonic log and occasionally combine it with

the density log to simulate a seismic wiggle trace.

Tie Synthetics:

Open Line MHD-101. The Wab Seismic horizon is at 0.520 sec, but the well top is at

0.945 sec. We will fix this.

LeftClick 00-03 well dot. It will double in size. RightClick >SynView. Maximize the

window. Scroll through data to familiarize yourself with the logs. Sonic first.

Shorter Density second, computed Interval Velocity, Reflection Coefficients,

Synthetic, and Seismic. Wavelet is displayed at top. Default is Ricker, but I prefer

Butterworth.

Edit Butterworth to 8/16/60/90 & 10/90% or Ricker to 45 Hz. (OK).

Tie Synthetic Wab at 0.480 sec. to the seismic at 0.517 sec. (Time shift mode), click on

synthetic peak, click on seismic peak. Synthetic will shift down.

Stretch synthetic to tie seismic. Synthetics almost always need to be stretched, seldom

compressed. Do not over do it, about 10-20% max. You should use interval

velocities for quality control. They must remain reasonable. Do not trust the

first or last few wavelets as they can be artifacts of bad data.

Look at synthetic peak at 0.848 sec and the seismic peak at 0.853 sec. Stretch from the

Jean Marie [0.650 sec] to here. (Time stretch mode). First click on the Jean Marie

peak indicating the top of the section to be stretched. Next, click on the

synthetic peak 0.848 sec. Third, click on the seismic peak at 0.853 sec.

Everything from 0.650 to 0.848 will be stretched.

(Remove last time stretch/shift) will undo last edit. Repeated clicking will back out each

edit until all are removed.

The synthetic peak at 0.963 will stretch to the seismic peak at 0.969. Stretch from the last

correlation at 0.853 sec.

The synthetic trough at 1.114 sec will stretch to the seismic trough at 1.152 sec. Stretch

from the last correlation at 0.969 sec.

Scroll through the data and examine the tie.

When satisfied, PDW Synthetics >Update Well Velocity & Synthetics. ID: ->2. (Add new

survey). Close window.

On Line MHD-101, zoom to well tie and Wab Group. The tie should be almost exact.

RightClick on well dot >Well Log Display… >Right Curve Display. Curve Name:

+Synthetic. Wiggle Fill *Right. Trace Deflection: 70%. Study synthetic tie.

To find which velocity survey is providing current velocity control, PDW Wells >

Well List Well ID +00-03, Component: Velocity/Synthetics Surveys. You will

see that Survey 2 is active. This is the synthetic we just created. You can

select between velocity surveys here. Close window.

 

Interpretation Break: Until End of Class

Experiment with Synthetics.

Generate Synthetic for Well 00-01.

Begin Interpreting:

Bluesky Fm peak

Wab Group peak (already done)

Fort Simpson trough

Slave Point peak

Fort Vermilion (already done)

Muskeg Fm weak peak

Keg River Fm weak trough

Study Log Ties:

Select various well logs and examine ties to seismic data. Often the quality of a synthetic

well tie can be evaluated by comparing sonic [DT] and other log breaks to the

seismic response.

 

Homework Due 1/23 at Beginning of Class:

Extend Well Top interpretations for these horizons: Bluesky Fm, WAB Group, Fort Simpson Fm, Slave Point Fm, Muskeg Fm, and Keg River Fm.

Be sure to edit bad seismic autopicks to best represent interpreted horizons. Remember when interpreting areas of weak signal, that horizons in this project tend to be parallel and your interpretations should be as smooth as the brightest seismic reflectors.

Manually edit horizons across fault on LBT-201. Remember that for normal faults, offset usually increases with depth. Because of increasing formation velocity with depth, offset in time may technically decrease, but honoring the data in this case may raise more questions than it answers. Therefore, try to force increasing time offset with depth whenever possible.

Make a print showing a close-up of the fault on LBT-201 with horizon offsets.

Make a print of Line MHD-101 showing horizon well ties.