# 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

1. Time structure maps with faults.
2. Depth structure maps.
3. Seismic facies maps for reservoir, source, or seal analysis.
4. Seismic amplitude maps for DHI analysis.
5. Thickness maps inferred from seismic tuning analysis.
6. Fault plane maps.
7. 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