Seismic exploration is the search for commercially economic subsurface deposits of crude oil, natural gas and minerals by the recording, processing, and interpretation of artificially induced shock waves in the earth. Artificial seismic energy is generated on land by vibratory mechanisms mounted on specialized trucks. Seismic waves reflect and refract off subsurface rock formations and travel back to acoustic receivers called geophones. The travel times (measured in milliseconds) of the returned seismic energy, integrated with existing borehole well information, aid geoscientists in estimating the structure (folding and faulting) and stratigraphy (rock type, depositional environment, and fluid content) of subsurface formations, and determine the location of prospective drilling targets.
Seismic exploration includes the following processes and activities:
- Review existing seismic and available data.
- Acquire, process and interpret new 2D seismic across concessions.
- Drill science well to evaluate reservoir characteristics by acquiring data in drilling phase, open hole logging, core analysis and production tests.
- Drill second well with potentially a horizontal section for further analysis and production tests .
The oil and gas industry uses 2D seismic, or seismic reflection, to analyze the structure of the rocks hidden beneath the surface. Seismic reflection involves sending acoustic energy into the ground (using an energy source such as a Vibroseis) to create a sound picture beneath the surface. Each stratigraphic layer within the Earth reflects a portion of the energy back and allows the rest to pass through. These reflected energy waves are recorded by sensitive receivers, or geophones, at the surface. Each receiver’s reading of the reflected energy waves is recorded onto magnetic tape then the shot location is moved along and the process repeated. Typically, the recorded signals are subjected to further processing before they are ready to be interpreted, an area of significant active research within industry and academia. In general, the more complex the geology of the area under study, the more sophisticated techniques are required to remove noise and increase resolution. Modern seismic reflection surveys contain large amount of data and so require large amounts of computer processing.
A 2D seismic profile is produced when the processing is complete – Step 1. The seismic profile below shows an interpreted cross section. Geoscientists use these profiles, in addition to nearby well information, to produce maps of the rocks buried below – Step 2. These maps allow the geoscientists to accurately position exploration wells in order to find oil and gas deposits.