What is 4D in oil and gas?
What is 4D in oil and gas?
Towed streamer seismic time-lapse technology (4D) is the dominant geophysical reservoir monitoring method applied for the purpose of optimising reservoir drainage.
What is a 3 D seismic survey?
In three-dimensional (3D) reflection seismic surveying the sound detectors (numbering up to a thousand or more) are spread out over an area and the sound source is moved from location to location through the area. 3D seismic programs are generally a uniform and evenly spaced grid of lines.
What is a 2D seismic survey?
A two dimensional (2D) seismic survey is an exploration method used to create a map of the structures beneath Earth’s surface (see image below). The different rock formations then reflect the waves back to the surface, where they are recorded over a period of time and converted into a seismic image.
How do you interpret seismic?
Step three: interpretation
- Time structure maps with faults.
- Depth structure maps.
- Seismic facies maps for reservoir, source, or seal analysis.
- Seismic amplitude maps for DHI analysis.
- Thickness maps inferred from seismic tuning analysis.
- Fault plane maps.
- Fault plane maps with cross-fault sand juxtaposition for seal analysis.
What can 4D seismic data be used for?
By analyzing differences of multiple seismic surveys acquired over a producing reservoir and by integrating with conventional reservoir monitoring data, 4D seismic data provides valuable insight on dynamic reservoir properties such as fluid saturation, pressure and temperature.
How does a 4D time lapse seismic response work?
Time Seismic Impedance 4D Seismic Amplitude and Time-shift Response for a Soft Sand Oil Reservoir Top Reservoir – a Negative Reflection Coefficient When “Water” replaces “Oil” => Velocity and Density increase => acoustic hardening – A reduction in seismic amplitude – An upward time-shift When “Gas” replaces “Oil” =>
What is the fourth dimension of a seismic survey?
The fourth dimension is time. So its a regular 3D seismic survey with receivers and sources laid over a 2 D surface array and sources fired to record data in the 3rd dimension, depth. This gives a 3D image that can be processed and rotated. 4D surveys are 3D surveys repeated in time, also called a time-lapse survey.
How does a 4D seismic response work for a soft sand reservoir?
4D Seismic Amplitude and Time-shift Response for a Soft Sand Oil Reservoir Top Reservoir – a Negative Reflection Coefficient When “Water” replaces “Oil” => Velocity and Density increase => acoustic hardening – A reduction in seismic amplitude – An upward time-shift When “Gas” replaces “Oil” => Velocity and Density decrease => acoustic softening