Seismic Imaging and Reservoir Characterization
Seismic imaging and reservoir characterization?
A reservoir characterization study is a part of the development of a reservoir model. This article describes some of the basic elements involved in a reservoir characterization study.
The use of seismic attributes to characterize reservoirs provides information on reservoir characteristics such as porosity, thickness, lithology, direct hydrocarbon indicators (bright spot, flat spot, and dim spot), and traps (faults, anticlines, synclines, and salt domes).
Seismic Imaging:
Seismic imaging is a technique that involves sending sound waves into the ground and measuring the reflections. This technique can provide detailed information about the structure of the reservoir and the distribution of fluids. Seismic imaging is less accurate than core analysis, but it can cover a large area quickly.
Seismic data provide an excellent image of structure and stratigraphy, but can be inverted to also provide a quantitative interpretation of porosity, permeability, water saturation etc.
Heterogeneity of Reservoir:
A large-scale structural perspective of the field of study, must involve all the parameters like reservoir geology, geochemistry, geo-mechanics, faults, fractures, and stress regimes are key to continue the process of reservoir characterization.
Seismic Reflection:
Seismic reflection is a powerful method used for imaging subsurface structures. It involves sending sound waves (or seismic waves) into the earths subsurface and recording the reflections that bounce back.
This data provides valuable insights into the subsurface architecture, including fault systems, stratigraphic layering, and potential hydrocarbon traps.
With advanced seismic acquisition techniques like 3D and 4D seismic surveys, geoscientists can create detailed images of reservoirs at different depths and time intervals, enhancing the accuracy of reservoir characterization.
Imaging techniques are essential tools in reservoir characterization as they enable geoscientists to visualize and understand subsurface structures and properties.
One widely used imaging technique is seismic imaging, which utilizes seismic waves to create detailed images of the subsurface. By analyzing seismic data, geoscientists can map structural features, identify faults and fractures, and estimate rock properties such as porosity and fluid content.
This analysis and detailed studies help the geoscientist to appropriately decide the location to be allotted for drilling or exploration.
Another important imaging tool is electromagnetic (EM) imaging. {I call it MRI of the reservoir}. This technique measures electromagnetic fields to detect variations in electrical properties, giving insights into hydrocarbon presence, lithology, and fluid distribution.
EM imaging can be particularly useful in unconventional reservoirs where traditional seismic methods may be limited.
QUOTE
UNQUOTE
Properties of the target reservoir:
A reservoir rock is a subsurface volume of rock that has sufficient porosity and permeability to permit the migration and accumulation of petroleum under adequate trap conditions. Porosity is a measure in percentage of pore volume or size of holes or vugs per unit volume of rock.
Seismic imaging can improve the structural and stratigraphic interpretation of the reservoir by revealing the geometry, continuity, and connectivity of the reservoir layers, faults, and fractures.
Rather than being limited to assisting in the identification and delineation of prospects, geophysics is now increasingly being used for the characterization of the internal geometry and quality of reservoirs themselves and is often used as a means of monitoring reservoir changes between wells during production.
The main purpose for completing a reservoir characterization process (the process) is to understand the opportunities and risks associated with an asset. The collection of subsurface data is the fundamental component in the process.
Data analysis tools can help you to identify reservoir properties, such as porosity, permeability, saturation, pressure, and temperature, and to evaluate reservoir performance, such as recovery factor, decline rate, and reserves. Some examples of data analysis tools are Petrel, Eclipse, OFM, and Kappa
The characterization of aquifers could be done using certain geophysical techniques like Electrical Resistivity, Electromagnetic Induction, Ground Penetrating Radar (GPR) and Seismic Techniques. Aquifer Characterization is dependent on the petro-physical properties (porosity, permeability, seismic velocities etc.)
Suitable reservoir rock:
In order to identify geological features in this image, geoscientist must quantify seismic signal parameters with attributes which are concerned with the subsurface stratigraphy. For opaque three dimensional seismic data, attributes are indispensable for visualizing and characterizing reflection properties.
The principle objective of seismic inversion is to transform seismic reflection data into a quantitative rock property, descriptive of the reservoir. In its most simple form, acoustic impedance logs are computed at each CMP. [In seismic data processing CMP refers to Common Mid-Point and CDP refers to Common Depth Point. Sometimes these two are used interchangeably but CDP is mainly used for dipping reflectors in subsurface.].
Reservoir Characterization:
1 Shared earth model.
2 Basic interpretation.
3 Premodeling organization.
4 Data preparation and formatting.
5 Exploratory data analysis (EDA)
6 3D structural modeling.
7 3D sedimentary modeling.
- 7.1 Stratigraphic model.
- 7.2 Facies model.
- 3D petrophysical modeling.
8. Flow Simulation
9. Model assumptions iteration and updating
Multicomponent seismic has also been commonly used to study seismic anisotropy, which allows us not only to produce better imaging and better definition of the reservoir, but also to determine the directional characteristics of the reservoir heterogeneities, such as aggregate alignments and cluster distribution.
It should be stressed that some methods used in seismic reservoir characterization are purely statistical and others are based on physical models. According to a group of remarkable authors, the optimum strategy is to combine the best of each method to generate results much more powerful than possible from purely statistical or purely deterministic techniques.
With accurate reservoir characterization, we can unlock more precise methods of resource extraction, revolutionize reservoir recovery strategies, reduce environmental impact and drive-up profitability.
PS: Above blog is available at the following links:
References:
1. Fred Aminzadeh, Shivaji N. Dasgupta, in Developments in Petroleum Science, 2013
2. Shib Sankar Ganguli, Vijay Prasad Dimri, in Developments in Structural Geology and Tectonics, 2023
3. Faruk Civan, in Reservoir Formation Damage (Second Edition), 2007
4. Huanqing Chen, in Fine Reservoir Description, 2022
5. Roger M. Slatt, in Developments in Petroleum Science, 2013
6. Mukerji, T., Avseth, P., Mavko, G., Takahashi, I., González, E.F., 2001, Statistical rock physics: Combining rock physics, information theory, and geostatistics to reduce uncertainty in seismic reservoir characterization, The Leading Edge,
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