Tiakina Te Moana

Prospecting for oil and gas using exploration seismology, a geophysical method of determining geologic structure by means of prospector-induced elastic waves. By studying body waves such as compressional and shear waves propagating through the Earth's interior, the constituent and elastic properties of its solid and liquid core, its solid mantle, and its thin crust are defined. The major differences between earthquake seismology and petroleum exploration seismology are scales and knowledge of the location of seismic disturbances. Earthquake seismology studies naturally generated seismic waves, which have periods in minutes and resolution in kilometers. In exploration seismology, artificial sources are used that have periods of tenths of a second and tens of meters of resolution. Production seismology requires higher-frequency seismic waves and better resolution, often resolution in the order of a few meters. See also Earth; Earth interior.

Computer technology allows resolution of some of the theoretical complexities of elastic wave propagation so that deeper insight into the wave field phenomena can be obtained. The availability of a large number of channels in the recording instrument facilitates three-dimensional and three-component acquisitions. Powerful supercomputers allow manipulation of larger and larger data sets, and they have facilitated display and interpretation of them as a single data unit through the use of advanced computer visualization techniques. See also Computer; Supercomputer.

The availability of powerful workstations led to the wide use of interactive processing and interpretation. When such is coupled with technically advanced algorithms, the amount of information that the interpreter can obtain from the data increases significantly. Better quality control is provided, fine-tuning analysis is achieved more easily, and the data can be enhanced to meet specific objectives. If there are discrepancies between the model and the real data, a hypothesis can be proposed based on information derived from the data. This process can be iterated until the Earth model derived is consistent with all available surface and subsurface geophysical, petrophysical, geological, and engineering data sets. See also Algorithm; Model theory; Simulation.

The seismic method as applied to exploration of oil and gas involves field acquisition, data processing, and geologic interpretation. Seismic field acquisition requires placement of acoustic receivers (geophones) on the surface in the case of land exploration, or strings of hydrophones in the water in the case of marine exploration. Seismic data processing is usually done in large computing centers with digital mainframe computers or a large number of processors in parallel configurations. The end result of seismic data processing is the production of a subsurface profile similar to a geologic cross section. It is commonly plotted in a time scale, but it is also possible to plot it in depth. These time or depth profiles are used for geologic interpretation. Geologic interpretation of seismic data has two key components, structural and stratigraphic. Structural interpretation of seismic data involves mapping of the geologic relief of different subsurface strata by using seismic data as well as information from boreholes and outcrops. Stratigraphic interpretation looks at attributes within a common stratum and interprets changes to infer varying reservoir conditions such as lithology, porosity, and fluid content.

Historically, surface seismic acquisition is done by placing sources and receivers along a straight line so that it can be assumed that all the reflection points fall in a two-dimensional plane formed between the line of traverse and the vertical. This is known as two-dimensional seismic. Three-dimensional seismic is a method of acquiring surface seismic data by placing sources and receivers in an areal pattern. One example of a simple three-dimensional layout is to place the receivers along a line and shoot into these receivers along a path perpendicular to this line. See also Computer graphics.

A three-dimensional seismic survey provides a more accurate and detailed image of the subsurface. It offers significantly higher signal quality than the two-dimensional data commonly acquired. It also improves both spatial and temporal resolutions. The three-dimensional seismic technique is being applied to exploration and production of oil and gas, accounting for more than half of the seismic activity in the Gulf of Mexico and North Sea.

Production seismology is the application of seismic techniques to problems related to the production and exploitation of petroleum reservoirs. Since production geophysics is the only effective method available that can image the reservoirs under in-place conditions, it has become an active field of applied research aimed at improving descriptions and understanding of reservoirs and their fluid flow behaviors. See also Geophysical exploration; Petroleum enhanced recovery; Petroleum geology; Petroleum reservoir engineering; Seismology.

Read more: http://www.answers.com/topic/seismic-exploration-for-oil-and-gas#ixzz1JOpHgqp3