Structural Interpretation

Question 1

Short sequence of activities => in order to good structural interpretation

Answer 1

1. Check storage and display POLARITY !!!!!!!!! (SEG; NON SEG)
2. Perform well-to-seismic match with synthetic seismograms
3. Correlate essential geological markers to reflections on seismic data
4. Correlate those horizons around between wells
5. Fill in remaining lines by interpretation
6. Create maps

Question 2

Aspects on well-to-seismic matching

Answer 2

• Search for boundaries with appreciable AI contrasts – record their character
• Determine main unconformities and local disconformities
• Minor time-shifts unimportant, character match vital
• Be aware of structural complications, i.e. faults
• Very close markers do not have added benefit

Question 3

Correlation of markers

Answer 3

• Create/select connecting random lines between all wells & interpret
• For deviated wells take line through the well-path
• Major faults may prevent complete round-correlation

Round correlation :

Two approaches
• Draw random lines between wells
• Draw one random line with kinks

Question 4

Extension - delta

Answer 4

• Syn-sedimentary faults “soling-out” • Sediment accretion at low side fault • Clastics only

Question 5

Extension régime features

Answer 5

• Listric faults, soling out in depth, occur in delta’s: growth at downthrown side and fault-plane reflections common
• Steep, occasionally rotated faultblocks in more competent rocks – “basement” induced
• Regular map image, few folds and many - smaller – faults.
• Mostly not, but severely faulted fields yield complicated maps (Gullfaks)

Question 6

Compressional régime

Answer 6

basement involved

• Multi-curved faults, steepening in case of basement involvement or flattening – overthrusting - with depth
• Often associated with strong folding
• Can yield complex map image, many folds with
relatively few, large faults
• Overthrusts, such as the Canadian Foothills, yield the most complex structures
• Trace interpretation systems cannot – yet – handle multi-valued horizons

Question 7

Wrenching régime

Answer 7

Trans-pression and trans-tension

Wrench régime characteristics
• Multi-curved, compounded faults, steepening with depth: “flowers”
• Correlation over faults difficult if not impossible
• Faults have laterally changing throw and/or
character
• Contemporaneous normal and reverse faulting can be present in a section
• Very complex map image

Question 8

Salt tectonics features

Answer 8

• Salt bodies exhibit highly variable shapes
• Flanks often impossible to interpret
• Halite acoustically transparent
• Characteristic secondary features – rimsynclines and caprocks
• Extensional faulting above salt domes, sometimes in radial pattern
• Seismic image below salt often seriously degraded