Changes

===Diagenesis===

===Diagenesis===

During and following burial, diagenetic events will modify the original pore network of reservoir rocks (see [[Evaluating diagenetically complex reservoirs]]). Four main diagenetic mechanisms affect reservoir quality: compaction, cementation, dissolution, and recrystallization These mechanisms are controlled by the detrital composition of the rock, burial depth, burial time, burial temperature, pore fluids, and pore fluid pressure.

During and following burial, diagenetic events will modify the original pore network of reservoir rocks (see [[Evaluating diagenetically complex reservoirs]]). Four main diagenetic mechanisms affect reservoir quality: compaction, cementation, dissolution, and recrystallization. These mechanisms are controlled by the detrital composition of the rock, burial depth, burial time, burial temperature, pore fluids, and pore fluid pressure.

===Compaction===

===Compaction===

Modern three-dimensional seismic data<ref name=pt06r17>Brown, A. R., 1986 Interpretation of three-dimensional seismic data: [http://store.aapg.org/detail.aspx?id=1025 AAPG Memoir 42], 194 p.</ref> can sometimes assist in predicting reservoir quality away from well control. Careful processing of seismic data allows a conversion of the seismic reflection amplitudes to estimates of acoustic impedance. Because lithology, porosity, and fluid saturations affect the acoustic impedance of a rock, a relationship can then be established between the seismic estimates of impedance and the rock properties determined from the logs or in the laboratory. (For information on comparing seismic data to rock properties, see [[Seismic inversion]].)

Modern three-dimensional seismic data<ref name=pt06r17>Brown, A. R., 1986 Interpretation of three-dimensional seismic data: [http://store.aapg.org/detail.aspx?id=1025 AAPG Memoir 42], 194 p.</ref> can sometimes assist in predicting reservoir quality away from well control. Careful processing of seismic data allows a conversion of the seismic reflection amplitudes to estimates of acoustic impedance. Because lithology, porosity, and fluid saturations affect the acoustic impedance of a rock, a relationship can then be established between the seismic estimates of impedance and the rock properties determined from the logs or in the laboratory. (For information on comparing seismic data to rock properties, see [[Seismic inversion]].)

Wireline logs can be classified into three different groups based on the information they provide: (1) lithology indicators—[[Basic open hole tools#Gamma ray|gamma ray]], sonic, density, and neutron logs, (2) porosity logs—sonic, density, and neutron logs, and (3) fluid saturation logs—resistivity logs.<ref name=pt06r6>Asquith, G., Gibson, C. 1982, [http://archives.datapages.com/data/alt-browse/aapg-special-volumes/me3.htm Basic well log analysis for geologists]: AAPG Methods in Exploration Series 3, 216 p.</ref> (For more on the information that wireline logs can provide, see [[Standard interpretation]].)

Wireline logs can be classified into three different groups based on the information they provide: (1) lithology indicators—[[Basic open hole tools#Gamma ray|gamma ray]], [[Basic open hole tools#Sonic|sonic]], [[Basic open hole tools#Density|density]], and [[Basic open hole tools#Compensated neutron|neutron]] logs, (2) porosity logs—sonic, density, and neutron logs, and (3) fluid saturation logs—resistivity logs.<ref name=pt06r6>Asquith, G., Gibson, C. 1982, [http://archives.datapages.com/data/alt-browse/aapg-special-volumes/me3.htm Basic well log analysis for geologists]: AAPG Methods in Exploration Series 3, 216 p.</ref> (For more on the information that wireline logs can provide, see [[Standard interpretation]].)

In addition to lithology, porosity, and fluid saturations, permeability sometimes can be inferred from log responses or a combination of log responses. The [[Basic open hole tools#Spontaneous potential|spontaneous potential]] log is most often used as a qualitative indicator of the permeability of a formation. (For more on wireline log response to reservoir properties, see [[Quick-look lithology from logs]].)

In addition to lithology, porosity, and fluid saturations, permeability sometimes can be inferred from log responses or a combination of log responses. The [[Basic open hole tools#Spontaneous potential|spontaneous potential]] log is most often used as a qualitative indicator of the permeability of a formation. (For more on wireline log response to reservoir properties, see [[Quick-look lithology from logs]].)