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Line 54: − − [[file:flow-units-for-reservoir-characterization_fig1.png|thumb|{{figure number|1}}Major types of geological and petrophysical data applied to flow unit zonation of a well. Here the flow units are delineated on the basis of permeability contrasts due to lithofacies changes and to the presence of a laterally continuous barrier to vertical permeability (flow unit 4). According to the definition of flow unit, it is permissible to define a flow unit that exhibits only weak flow or no flow through it. This property of flow units makes it possible to use a single numbering system for identifying both obvious flow units and probable permeability barriers that can be mapped at the same scale as reservoir quality flow units.]]
Flow units for reservoir characterization (view source)
Revision as of 17:26, 20 January 2014
, 17:26, 20 January 2014→Methods of defining flow units
==Methods of defining flow units==
==Methods of defining flow units==
There is no universally applicable set of rules by which to define flow units. Dividing a reservoir into flow units requires an integration of stratigraphic, sedimentological, structural, petrographic, petrophysical, and field performance data. The process is summarized as follows (Figure 1):
[[file:flow-units-for-reservoir-characterization_fig1.png|thumb|{{figure number|1}}Major types of geological and petrophysical data applied to flow unit zonation of a well. Here the flow units are delineated on the basis of permeability contrasts due to lithofacies changes and to the presence of a laterally continuous barrier to vertical permeability (flow unit 4). According to the definition of flow unit, it is permissible to define a flow unit that exhibits only weak flow or no flow through it. This property of flow units makes it possible to use a single numbering system for identifying both obvious flow units and probable permeability barriers that can be mapped at the same scale as reservoir quality flow units.]]
There is no universally applicable set of rules by which to define flow units. Dividing a reservoir into flow units requires an integration of stratigraphic, sedimentological, structural, petrographic, petrophysical, and field performance data. The process is summarized as follows ([[:file:flow-units-for-reservoir-characterization_fig1.png|Figure 1]]):
* Identify the major lithofacies, vertical sequences, and depositional environments from available core. Relate lithofacies, at the whole-core scale, to their mineralogical, textural, and pore level properties and to permeability, [[porosity]], fluid saturations, and capillarity as measured on core plugs. Establish consistent relationships between rock properties and petrophysical properties.
* Identify the major lithofacies, vertical sequences, and depositional environments from available core. Relate lithofacies, at the whole-core scale, to their mineralogical, textural, and pore level properties and to permeability, [[porosity]], fluid saturations, and capillarity as measured on core plugs. Establish consistent relationships between rock properties and petrophysical properties.
* Establish the three-dimensional distribution of flow units by correlation of calibrated wireline logs. Knowledge of environments of deposition of the reservoir sequence is important to interpreting the style of correlation to be used and the expected patterns of external and internal geometry of any flow unit (see [[Lithofacies and environmental analysis of clastic depositional systems]]). During correlation, the flow unit zonation established in individual cored wells may change somewhat. Tying correlation horizons around a loop is critical because individual correlation sections alone can be deceptive.
* Establish the three-dimensional distribution of flow units by correlation of calibrated wireline logs. Knowledge of environments of deposition of the reservoir sequence is important to interpreting the style of correlation to be used and the expected patterns of external and internal geometry of any flow unit (see [[Lithofacies and environmental analysis of clastic depositional systems]]). During correlation, the flow unit zonation established in individual cored wells may change somewhat. Tying correlation horizons around a loop is critical because individual correlation sections alone can be deceptive.
* Test the validity of flow units established by consideration of production logs (see [[Production engineering methods]]), flow tests of small intervals, oil and water geochemistry (see [[Laboratory methods]]), repeat formation tester (RFT) surveys (see [[Wireline methods]]), injectivity logs, tracer surveys, and any available data on patterns of production through time. Modify the flow unit definitions as needed to accommodate the physical measurements of flow, if a rationale can be found for the differences.
* Test the validity of flow units established by consideration of production logs (see [[Production engineering methods]]), flow tests of small intervals, oil and water geochemistry (see [[Laboratory methods]]), repeat formation tester (RFT) surveys (see [[Wireline methods]]), injectivity logs, tracer surveys, and any available data on patterns of production through time. Modify the flow unit definitions as needed to accommodate the physical measurements of flow, if a rationale can be found for the differences.
The distribution of petrophysical properties such as porosity and permeability can be mapped within flow units using well control only or by applying geostatistical procedures to create stochastic realizations of these distributions “conditioned” on the well data (see [[Geological methods]]). Geostatistical techniques that have a strong stochastic component are consistent with, and complementary to, the flow unit concept, which is itself mostly deterministic.
The distribution of petrophysical properties such as porosity and permeability can be mapped within flow units using well control only or by applying geostatistical procedures to create stochastic realizations of these distributions “conditioned” on the well data (see [[Geological methods]]). Geostatistical techniques that have a strong stochastic component are consistent with, and complementary to, the flow unit concept, which is itself mostly deterministic.