Changes

A ''flow unit'' is defined as a mappable portion of the total reservoir within which geological and petrophysical properties that affect the flow of fluids are consistent and predictably different from the properties of other reservoir rock volumes (modified from <ref name=pt06r31 />). Flow units have the following characteristics in common:

A ''flow unit'' is defined as a mappable portion of the total reservoir within which geological and petrophysical properties that affect the flow of fluids are consistent and predictably different from the properties of other reservoir rock volumes (modified from <ref name=pt06r31 />). Flow units have the following characteristics in common:

{{quotation|1. ''A flow unit is a specific volume of a reservoir, which is composed of one or more [[reservoir quality]] lithologies and any nonreservoir quality rock types within that same volume, as well as the fluids they contain''.

{{quotation|1. ''A flow unit is a specific volume of a reservoir, which is composed of one or more [[reservoir quality]] lithologies and any nonreservoir quality rock types within that same volume, as well as the fluids they contain''.}}

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Flow units are internally consistent, but not necessarily homogeneous, in terms of either geological or petrophysical properties. They may contain more than one reservoir quality lithology and they may include nonreservoir features such as shales and cemented layers. Petrophysical properties may correspond to those of lithofacies defined geologically. However, petrophysical similarities among lithofacies may indicate that those lithofacies should be grouped into a single flow unit if they are contiguous. Alternatively, petrophysical dissimilarities within a geologically defined lithofacies may dictate that subdivision of a single lithofacies into several flow units is warranted. A flow unit zonation differs in principle from a lithofacies zonation in that it integrates geological, petrophysical, and production data with the end purpose of describing fluid flow pathways in the reservoir, not the distribution of depositionally distinctive lithologies.

Flow units are internally consistent, but not necessarily homogeneous, in terms of either geological or petrophysical properties. They may contain more than one reservoir quality lithology and they may include nonreservoir features such as shales and cemented layers. Petrophysical properties may correspond to those of lithofacies defined geologically. However, petrophysical similarities among lithofacies may indicate that those lithofacies should be grouped into a single flow unit if they are contiguous. Alternatively, petrophysical dissimilarities within a geologically defined lithofacies may dictate that subdivision of a single lithofacies into several flow units is warranted. A flow unit zonation differs in principle from a lithofacies zonation in that it integrates geological, petrophysical, and production data with the end purpose of describing fluid flow pathways in the reservoir, not the distribution of depositionally distinctive lithologies.

{{quotation|2. ''A flow unit is correlative and mappable at the interwell scale''.

{{quotation|2. ''A flow unit is correlative and mappable at the interwell scale''.}}

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Because flow units are deterministic elements in a reservoir description, they must be of a scale that is correlative and mappable relative to well spacing. Flow units should be continuous at interwell scales, but they need not extend across the entire reservoir. Because some parts of a reservoir can be efficiently drained only on closer well spacings, the definition of some flow units may change with infill drilling and changes in production mechanism (such as initiation of [[waterflooding]]) during field life.

Because flow units are deterministic elements in a reservoir description, they must be of a scale that is correlative and mappable relative to well spacing. Flow units should be continuous at interwell scales, but they need not extend across the entire reservoir. Because some parts of a reservoir can be efficiently drained only on closer well spacings, the definition of some flow units may change with infill drilling and changes in production mechanism (such as initiation of [[waterflooding]]) during field life.

{{quotation|3. ''A flow unit zonation is recognizable on wireline logs''.

{{quotation|3. ''A flow unit zonation is recognizable on wireline logs''.}}

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Mappability in the subsurface requires that flow units be recognizable on wireline logs. Flow units recognizable only in core are useful only if all wells have been cored. Some method must be found to translate a flow unit zonation based on core to a zonation based on the wireline log suite available in a particular reservoir.

Mappability in the subsurface requires that flow units be recognizable on wireline logs. Flow units recognizable only in core are useful only if all wells have been cored. Some method must be found to translate a flow unit zonation based on core to a zonation based on the wireline log suite available in a particular reservoir.

{{quotation|4. ''A flow unit may be in communication with other flow units''.

{{quotation|4. ''A flow unit may be in communication with other flow units''.}}

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Flow units may be in communication with one another across their boundaries, both in terms of pressure and in the ability of fluids to move vertically and laterally, or they may be completely isolated from one another by [[permeability]] barriers.

Flow units may be in communication with one another across their boundaries, both in terms of pressure and in the ability of fluids to move vertically and laterally, or they may be completely isolated from one another by [[permeability]] barriers.