Geophysics Seismic Survey Service -
Data Processing, Recording, Test
A seismic survey is a method used to explore and map the subsurface of the Earth. The primary purpose of a seismic survey is to locate and assess the size and shape of potential hydrocarbon (oil and gas) reservoirs, but it can also be used to explore for other types of subsurface resources, such as mineral deposits, and to study the geology of the Earth’s crust.
Seismic surveys use a combination of geophysics and geology to create images of the subsurface. The primary tool used in a seismic survey is a seismic source, which generates a controlled impulse of energy, typically in the form of a loud noise or a vibration. This energy travels through the Earth and is reflected back to the surface by different subsurface layers, such as rock formations or underground reservoirs. The reflections are detected by a series of sensors, called geophones or hydrophones, which are placed on the surface or in boreholes.
Types Of Seismic Survey Exploration
1D Seismic Exploration
Also known as vertical seismic profiling (VSP), involves collecting data along a single vertical line, typically by using a borehole or a geophone placed at a single location. This type of survey provides a detailed image of the subsurface at a specific location and is used to study the geology and fluid content of a particular subsurface formation.
2D Seismic Exploration
Involves collecting data along a single line, or a series of closely spaced lines, across an area of interest. The data collected is used to create a cross-sectional image of the subsurface, showing the different layers of rock and other subsurface features that the seismic energy encountered as it passed through the Earth. This type of survey is used to understand the geology and structural geology of an area, such as fault and fold patterns, and also used in hydrocarbon exploration and production.
3D Seismic Exploration
Is the most advanced and data-intensive type of seismic survey, it involves collecting data over a much larger area, typically a grid of many closely spaced lines. The data is then used to create a three-dimensional image of the subsurface, providing a much more detailed and accurate view of the subsurface geology and the location of subsurface features such as hydrocarbon reservoirs. This type of survey is used for detailed reservoir characterization, such as to detect subtle changes in rock properties or fluid content that may indicate the presence of hydrocarbons or other subsurface resources.
1D, 2D, and 3D seismic exploration, in terms of the increasing dimensionality of data and images, have increasing cost and complexity, but also have increasing resolution, detail, and accuracy. The choice of which survey to use depends on the specific exploration or research goals and the geology of the area being studied.
Different Types Of Seismic Methods
Some of the main types of seismic surveys include:
Refraction Seismic Surveys
This type of seismic survey is used to measure the refraction, or bending, of seismic energy as it travels through the Earth. It is used to determine the velocity of subsurface materials and to create a less detailed subsurface image compared to reflection seismic.
Reflection Seismic Surveys
This is the most common type of seismic survey and is used to create images of the subsurface by measuring the reflection of seismic energy from subsurface rock formations and other subsurface features. It is divided into two main categories: 2D and 3D
Surface - Wave Seismic Surveys
Also known as surface-wave analysis or surface-wave testing, is a type of passive seismic survey that is used to study the shallow subsurface. The main principle is to measure the ground motion caused by surface waves, which are a type of seismic wave that travels along the surface of the Earth. These waves can be generated naturally by earthquakes, wind, or ocean waves, or they can be artificially generated by mechanical or vibroseis sources
Each of these different types of seismic surveys has its own strengths and weaknesses, and the choice of which survey to use depends on the specific exploration or research goals and the geology of the area being studied.
What Is The Application And
Benefits Of The Seismic Survey Method?
Some of the main applications and benefits of seismic surveys include:
The primary application of seismic surveys is to locate and assess the size and shape of potential hydrocarbon (oil and gas) reservoirs. Seismic data can be used to identify subsurface structures that are likely to contain hydrocarbons, to estimate the size and shape of the reservoirs, and to identify the most promising drilling locations.
Seismic surveys can also be used to explore for other types of subsurface resources, such as mineral deposits. The data can be used to identify subsurface structures that are likely to contain valuable minerals and to estimate the size and shape of the deposits.
Environmental and Engineering Studies
Seismic surveys can be used to study the geology of the Earth’s crust and to map subsurface soil and rock layers. This information can be used to predict site effects such as soil liquefaction and lateral spreading and to study the properties of the shallow subsurface such as ground water, soil and rock properties.
Safety and Risk Assessment
Seismic surveys can also be used to map subsurface hazards such as sinkholes, buried mines, and other potential hazards.
Seismic survey is a non-destructive method of exploring the subsurface. It does not require drilling, excavation or other invasive procedures, which can cause damage to the environment and to surface structures.
Seismic survey can be a cost-effective way to explore the subsurface. It can be used to target drilling locations more accurately, which can help to reduce the number of dry wells and the overall cost of exploration.
Seismic survey can provide high-resolution images of the subsurface, which can be used to make more accurate exploration and production decisions.
Seismic survey can be completed in a relatively short time-frame, which allows for quick results to be obtained and for exploration to progress quickly.
Seismic survey can be conducted on land and offshore in both shallow and deep water environments.
In summary, Seismic survey methods are versatile, non-destructive, cost-effective, high-resolution and time-efficient tools that can be used to explore the subsurface of the earth for hydrocarbons and other resources, and to study the geology of the Earth’s crust.
How Many Types Of Seismic Instruments Are There?
Some of the main types of seismic instruments we use are;
Active Seismic Instruments
Use an energy source, such as a vibrator or an air gun, to introduce energy into the subsurface. This energy travels through the Earth and is reflected back to the surface by subsurface layers, such as rock formations or underground reservoirs. The reflections are detected by sensors, such as geophones or hydrophones, which are placed on the surface or in boreholes. Active seismic instruments are typically used in reflection seismic surveys, which are the most common type of seismic survey and are used to create images of the subsurface by measuring the reflection of seismic energy.
Passive Seismic Instruments
On the other hand, rely on natural sources of energy, such as earthquakes or ocean waves, to introduce energy into the subsurface. These instruments detect the ground motion caused by the seismic waves as they travel through the Earth. Passive seismic instruments are typically used in microtremor surveys, surface-wave seismic surveys, and passive seismic tomography. These types of survey can be used to study the shallow subsurface geology, near-surface soil properties and site effects such as soil liquefaction and lateral spreading.
Active seismic surveys are generally more expensive and time-consuming to acquire compared to passive seismic surveys. The main advantage of passive seismic surveys is that they can be conducted continuously, providing long-term monitoring of subsurface properties, and also are less invasive and less likely to have an environmental impact.
Active seismic surveys, however, provide more detailed images of the subsurface, which can be used to make more accurate exploration and production decisions. The choice of which method to use depends on the specific exploration or research goals and the geology of the area being studied.
What Are The 4 Types Of Seismic Waves?
P-waves (Primary Waves)
P-waves are the fastest type of seismic wave and are the first to arrive at a seismic station. They travel through the Earth by pushing and pulling the ground in the same direction as the wave is moving. P-waves can travel through solids, liquids, and gases and are the most common type of seismic wave used in exploration seismology.
S-Waves (Secondary Waves)
S-waves are slower than P-waves and arrive at a seismic station after P-waves. They travel through the Earth by shaking the ground up and down and at right angles to the direction of the wave. S-waves can only travel through solid materials and are used to study the deeper structure of the Earth.
Rayleigh waves are surface waves that travel along the surface of the Earth. They are caused by the combination of P and S waves and move the ground in an elliptical motion, which causes the ground to rise and fall, and move from side to side. Rayleigh waves are responsible for most of the ground motion that is felt during an earthquake.
Love waves are also surface waves but unlike Rayleigh waves, which move the ground in an elliptical motion, Love waves move the ground horizontally. They can be more destructive than Rayleigh waves because they can cause strong shaking and ground displacement in the direction perpendicular to the direction of the wave propagation.