Changes

==From Acquisition to Seismic Trace==

==From Acquisition to Seismic Trace==

Seismic data acquisition is done by geophysicists where source is shot into subsurface. Then, the wave propagate and is reflected on rock boundary. After that, the wave that is reflected propagates with different path to surface and is recorded by geophone. The wave that is recorded is P wave. This wave consist of direct wave, reflected wave, refracted wave and noise. Amplitude that wants to be interpreted in oil and gas industry commonly is only reflected waves. Therefore, Geophysicists processing the data to reduce amplitude effect from another waves. The seismic data after processing can be classified to be post-stack and pre-stack data. Post-stack data analyze seismic data with zero offset amplitude, while pre-stack data analyze seismic data with non-zero offset amplitude.  

Seismic data acquisition is done by geophysicists where source is shot into subsurface. Then, the wave propagate and is reflected on rock boundary. After that, the wave that is reflected propagates with different path to surface and is recorded by geophone. The wave that is recorded is P wave. This wave consist of direct wave, reflected wave, refracted wave and noise. Amplitude that wants to be interpreted in oil and gas industry commonly is only reflected waves. Therefore, Geophysicists processing the data to reduce amplitude effect from another waves. The seismic data after processing can be classified to be post-stack and pre-stack data. Post-stack data analyze seismic data with zero [[offset]] amplitude, while pre-stack data analyze seismic data with non-zero offset amplitude.  

[[File:Aapg 2.png|350px|thumbnail|right|Figure 2 Acquisition Seismic Data.<ref>Boyer, S. and Mari, J.L (1997). Seismic Surveying and Well Logging. Paris: Technip</ref>]]

[[File:Aapg 2.png|350px|thumbnail|right|Figure 2 Acquisition Seismic Data.<ref>Boyer, S. and Mari, J.L (1997). Seismic Surveying and Well Logging. Paris: Technip</ref>]]

==Factors That Influences Amplitude==

==Factors That Influences Amplitude==

Factors that influences velocity of wave are porosity, density, temperature, grain size, gas saturation, frequency, external pressure, pore pressure and stress. The curve between P wave velocity and various parameters are shown in the figure below. The most influential factor on the P wave velocity changes include porosity, gas saturation, external pressure and pore pressure. The relationship between gas saturation and P wave velocity drops drastically resulting in the formation of anomalies such as DHI, AVO, and others.  

Factors that influences velocity of wave are porosity, density, temperature, [[grain size]], gas saturation, frequency, external pressure, pore pressure and stress. The curve between P wave velocity and various parameters are shown in the figure below. The most influential factor on the P wave velocity changes include porosity, gas saturation, external pressure and pore pressure. The relationship between gas saturation and P wave velocity drops drastically resulting in the formation of anomalies such as DHI, AVO, and others.  

[[File:Aapg 7.png|300px|thumbnail|center|Figure 7 Some Parameter That Influence to P Wave Velocity<ref>Hilterman, F. J., 2001, Seismic amplitude interpretation: short course notes. Distinguished Instructor Series no. 4. Society of Exploration Geophysicists, Tulsa, Oklahoma</ref>]]

[[File:Aapg 7.png|300px|thumbnail|center|Figure 7 Some Parameter That Influence to P Wave Velocity<ref>Hilterman, F. J., 2001, Seismic amplitude interpretation: short course notes. Distinguished Instructor Series no. 4. Society of Exploration Geophysicists, Tulsa, Oklahoma</ref>]]