Seismic Data Interpretation
The seismic data interpretation is final and most crucial stage of seismic API cycle.
Seismic interpretation is the process of analysing seismic data for creating a geological model of earth’s subsurface. The main goal is to identify and map subsurface structures, stratigraphy and reservoir properties.
Basic steps in Seismic Data Interpretation
Display and Amplitude Mapping
Display and visualised processed seismic sections into different colour combinations to analyze variations in seismic amplitudes with offsets.
Structural Interpretation
Horizon Picking: Interpreter identify and map key seismic reflectors.
Timing: Measure the two-way reflection time from datum to the picked reflector or horizon. Note down the timing in milliseconds.
Posting: The measured reflection times can be transferred to corresponding shot point or CMP location on the base map.
Contour or Time Structure Map : Connecting the equal values of timing, into contour using an easily identifiable contour interval (e.g. 200ms). The contour map helps interpreter to identify structures, the relief and closure of the interpreted horizons, and potential target such as Oil-Water-Contact (OWC). The preparing structural contour map is the ultimate goal of the structural interpretation.
Fault Interpretation
The main aim of the fault interpretation is to identify and map the locations, orientations and extends of the faults in the subsurface.
Mapping of the Faults: Interpreter identify and draw the fault line on seismic section, it is also correlated with horizon displacement at the location to reconfirm.
Method of Locating Faults: First of all identify the fault closure and mark by the following point up to the top of the seismic section, and mark the location of the fault to the corresponding shot-point or CMP location of the seismic line.
Posting of Faults on Base Map: The plotting of fault location on the base map, to the corresponding inline and shot point location, ensuring to indicate the proper fault direction on base map.
Now, repeat the process of plotting the fault locations on the map for all the neighbouring inlines and crosslines. Finally, draw a connecting line between the fault locations, which will tell us the location and orientation of the faults on base map.
Stratigraphic Interpretation
In main objectives of the stratigraphic interpretation is to analyse and understand the sequence of rock layers, their compositions, and distribution of sedimentary rocks in the subsurface.
There are various type of stratigraphic analysis, such as analysis of depositional sequence of the stratigraphy, lithostratigraphy, biostratigraphy, choronostratigraphy and facies analysis.
Attribute Analysis
Seismic attributes are used in interpretation to enhance the visualisation and understanding of subsurface geological features. The seismic attributes can enhance geologic features like fold, faults and fractures in the subsurface, attributes making them more easier to identify.
There are several type of seismic attributes, which we can use in seismic interpretation such coherence, curvature, dip and azimuth in structural interpretations, the seismic amplitude, frequency and phase in stratigraphic interpretations, impedance inversion, spectral decomposition and elastic attributes (Poisson rotio, Lamda-rho, Mu-rho) in reservoir characterisation. Amplitude anomaly such as AVO, flat spot, dim-spot and bright spot in direct hydrocarbon detection. The texture attributes helps interpreter in identify and classifying the seismic facies, by identifying the reflection amplitude strength, continuity and shape.
Geological Modelling
This is most important stage of seismic interpretation, the main purpose of geological modelling is to create detailed 3D model of subsurface geological structures, and rock properties by integrating all the interpretations. This can helps in understanding the spatial distribution of rocks, geological structures and fluid properties in the subsurface.
Integration and Validation
The integration of all the available information is important validate the model accuracy and reliability of subsurface models.
Learn More About Seismic
Click 👉 Seismic Data Acquisition
Click 👉 Seismic Survey Geometry
Click 👉 Seismic Data Processing
Click 👉 Seismic Depth Imaging
Click 👉 Seismic Data Interpretations