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ISTANBUL UNIVERSITY. ASSOCIATE PROF.DR. HÜSEYİN TUR. Basic seismic interpretation. RECORDING SEISMIC DATA. Compressional (P) and Shear (S) waves. P wave: the fastest kind of seismic wave. The P wave can move through solid rock and fluids
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ISTANBUL UNIVERSITY ASSOCIATE PROF.DR. HÜSEYİN TUR
Compressional (P) and Shear (S) waves • P wave: the fastest kind of seismic wave. The P wave can move through solid rock and fluids • S wave: slower than a P wave and can only move through solid rock
P-wave Source CMP CCP 3C/4C Receiver Surface/ seafloor Incident P-waves Reflected P-wave Reflected Mode Converted S-wave (SV) Reflector Transmitted P and SV waves
Basic reflection theory • Refected and Transmitted waves • Reflection coefficient • the velocity increases across the interface the reflection coefficient will be positive (peak) • RC's are negative when moving from a high velocity to a low velocity (trough) Phase: Refers to the SHAPE of a wavelet Polarity: Only has positive and negative conditions
Bright Spot Dim spot and Flat Spot • Bright spot is preresented with high ampliture indicacate low velocity gas sand. Sometime bright spot may exist because of some lithologic variation • Dim spot have nearly the same velocity between two layers. • Flat spot is a reflection from the flat upper surface of a liquid, that is a contact between a liquid and a gas. Only recognizable when theother reflections around it are not flat
Velocity Some factors effect to velocity: • Compaction (depend on depth) • Lithology (limestone>sandstone) • Porosity • Pore fluid type (H2O>Oil>Gas) • Geologic age
Workflow Geology 2D Seismic data acquisition 3D seismic data acquisition Seismic data processing Seismis data interpretation Time to depth conversion Location to Drill
Interpretation workflow (3D) IESX Grid and Contour map Display basemap and seis2Dv/3Dv Interpret faults Interpret horizons, create fault contacts Create fault boundaries CPS-3 Time to depth conversion Depth map Volumetric calculation Location To drill
Display Basemap 2D line 3D Survey 3D inline) Crossline: 500-770, Increment: 20 2D CDP increment: 50
Display Seis2DV/3DV • Display style: VI: variable intensity wiggle trace VA VI
Source Points 4C Receivers In-line Geophone N Cross-line Geophone IN-LINE AND CROSS-LINE
Method to pick the Faults Inline 570: parallel to Fault strike Crossline 570: perpendicular to Fault strike
Interpret Faults Fault location
Interpret Horizons Horizon_1 Horizon_2
Create fault boundaries Fault_3 Fault_2 Horizon_2 Horizon_1 Fault_1
Grid and Contour Horizon_1 Time map with Fault boundaries Time map with no Fault boundaries Time: 680-770 (ms) Gridding>structural Gridding
Grid and Contour Horizon_2 Time map with Fault boundaries Time map no fault boundaries Time: 940-1110 (ms)
Create Depth Map Horizon_1: 1959-2265 (ft) Horizon_2: 2900-3536 (ft) Interval: 20 (ft) Interval: 25 (ft)
Location to drill drill model seismic