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  | isbn    = 0891816607

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Major variations in levels of [[reservoir quality]] and degrees of lateral and vertical continuity within oil and gas fields are controlled primarily by depositional factors (see other chapters). However, major inhomogeneities may also be produced by diagenetic alterations. These inhomogeneities in rock properties may transect or reverse trends produced by depositional controls and can significantly influence reservoir properties, including initial fluid saturations, residual saturations, waterflood sweep efficiencies, preferred directions of flow, and reactions to injected fluids. Extreme [[permeability]] stratification or the development of permeability barriers by diagenetic alteration may lead to the need to drill additional infill wells or reposition the locations of such wells, selectively perforate and inject reservoir units, manage zones on an individual basis, and revise decisions regarding suitability for thermal recovery operations.

Major variations in levels of [[reservoir quality]] and degrees of lateral and vertical continuity within oil and gas fields are controlled primarily by depositional factors. However, major inhomogeneities may also be produced by diagenetic alterations. These inhomogeneities in rock properties may transect or reverse trends produced by depositional controls and can significantly influence reservoir properties, including initial fluid saturations, residual saturations, waterflood sweep efficiencies, preferred directions of flow, and reactions to injected fluids. Extreme [[permeability]] stratification or the development of permeability barriers by diagenetic alteration may lead to the need to drill additional infill wells or reposition the locations of such wells, selectively perforate and inject reservoir units, manage zones on an individual basis, and revise decisions regarding suitability for thermal recovery operations.

A ''diagenetically complex reservoir'' is a reservoir in which the major inhomogeneities affecting fluid distribution and/or productivity are controlled primarily by diagenetic events. Diagenetic inhomogeneities are zones of reduced or enhanced [[porosity]] and/or permeability that are generated by one or a combination of the processes of cementation, compaction, replacement, dissolution, and fracturing. For a reservoir to be considered complex, the diagenetic inhomogeneities must exhibit a complex distribution that is not directly correlated with or controlled by depositional factors.

A ''diagenetically complex reservoir'' is a reservoir in which the major inhomogeneities affecting fluid distribution and/or productivity are controlled primarily by diagenetic events. Diagenetic inhomogeneities are zones of reduced or enhanced [[porosity]] and/or permeability that are generated by one or a combination of the processes of cementation, compaction, replacement, dissolution, and fracturing. For a reservoir to be considered complex, the diagenetic inhomogeneities must exhibit a complex distribution that is not directly correlated with or controlled by depositional factors.

| Log correlation

| Log correlation

| Rapid; inexpensive

| Rapid; inexpensive

| May not provide unique solution; results dependent on ability to correlate lithology to unique log response<br>Degree of confidence low if zones correlated are thin or well spacing is large<br>Requires modern log suite (GR, density, neutron, or sonic)

| May not provide unique solution; results dependent on ability to correlate lithology to unique log response<br>Degree of confidence low if zones correlated are thin or well spacing is large<br>Requires modern log suite ([[Basic open hole tools#Gamma ray|GR]], [[Basic open hole tools#Density|density]], [[Basic open hole tools#Compensated neutron|neutron]], or [[Basic open hole tools#Sonic|sonic]])

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| Fluid distribution

| Fluid distribution