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 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 S wave: slower than a P wave and can only move through solid rock

Reflected Mode Converted S-wave (SV) Surface/ seafloor Reflector P-wave Source 3C/4C Receiver CMPCCP ReflectedP-wave Incident P-waves Transmitted P and SV waves

Basic reflection theory Refected and Transmitted waves Refected and Transmitted waves Reflection coefficient 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) 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 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. 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 the other reflections around it are not flat 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 the other 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 2D Seismic data acquisition Seismic data processing Seismis data interpretation 3D seismic data acquisition Time to depth conversion Geology Location to Drill

Seismic data interpretation

Interpretation workflow (3D) Display basemap and seis2Dv/3Dv Interpret faults Interpret horizons, create fault contacts Create fault boundaries Grid and Contour map IESX CPS-3 Time to depth conversion Depth map Volumetric calculation Location To drill

Display Basemap 3D Survey 2D line 3D inline) Crossline: , Increment: 20 2D CDP increment: 50

Display Seis2DV/3DV Display style: Display style: VI: variable intensity wiggle trace VI: variable intensity wiggle trace VAVI

IN-LINE AND CROSS-LINE Source Points 4C Receivers In-line Geophone Cross-line Geophone  N

Method to pick the Faults Inline 570: parallel to Fault strikeCrossline 570: perpendicular to Fault strike

Interpret Faults Fault location

Interpret Horizons Horizon_1Horizon_2

Create fault boundaries Fault_2 Fault_1 Fault_3 Horizon_1 Horizon_2

Grid and Contour Horizon_1 Time map with Fault boundariesTime map with no Fault boundaries Time: (ms) Gridding>structural Gridding

Grid and Contour Horizon_2 Time map with Fault boundariesTime map no fault boundaries Time: (ms)

Time to Depth Conversion

Create Depth Map Horizon_1: (ft)Horizon_2: (ft) Interval: 25 (ft)Interval: 20 (ft)

Location to drill modelseismic drill