Lecture 10: Seismic Stratigraphy:Lecture 10: Seismic Stratigraphy:

Amplitide: Thick lines = high amplitude.alternating rock properties or environments.

Thinner more sporadic lines = low amplitude.stable environments chalk.

Continuity: Broken up lines = discontinuous.environments that quickly change laterally.Fluvial/alluvial.

Trace lines laterally = continuous.Stable uniform environments.Deep-marine/Lactustrine.

Frequency: Lines close together = high frequency.

Lines spaced out, discontinuous = low frequency.

Interval Velocity: Can calculate intervals from acoustic impedance sections. Extreme velocities may be indicative of a lithology.Anomalously low = gas sand.Anomalously high = limestone, salt, coal.

Seismic Reflections as Timelines:e.g. Prograding Delta.Sands in proximal end Muds in distal end.This is a gradual transition so no reflectors over the boundaries. Without an abrupt change there will be no reflector.However there are often pauses in the sedimentation. This allows differential digenesis/lithification along a time line.

Seismic Sequence:Genetically related sediments normally comprise of a sequence of concordant strata that exhibit discordance with under and overlying sequences.i.e. they are bounded by unconformities or their correlative conformities.

Seismic Facies Analysis:Environment and lithofacies are interpreted from seismic data.Groups of reflectors that have parameters such as amplitude, frequency and continuity that differ from adjacent groups.

Facies Geometry:Consists of external forms and internal reflection configurations. Interpreted in terms of sedimentary environment then lithological potential. If the environment has enough energy to move sand grains then it is interpreted as sand prone.