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Stratigraphically complex fields are those that exhibit a high degree of vertical and lateral heterogeneity that is directly controlled by the environment of deposition (Table 1). This heterogeneity occurs at all scales (see [[Geological heterogeneities]]). It can result in a highly variable distribution of rock properties within one reservoir and the division of a single stratigraphic interval into multiple reservoirs that act as independent, self-contained compartments.

Stratigraphically complex fields are those that exhibit a high degree of vertical and [[lateral]] heterogeneity that is directly controlled by the environment of deposition (Table 1). This heterogeneity occurs at all scales (see [[Geological heterogeneities]]). It can result in a highly variable distribution of rock properties within one reservoir and the division of a single stratigraphic interval into multiple reservoirs that act as independent, self-contained compartments.

==Degree of hetrogeneity==

==Degree of hetrogeneity==

{| class = "wikitable"

{| class = "wikitable"

|-

|-

|+ {{table number|1}}Tentative, relative depositional heterogeneity ranking of reservoir facies based primarily on Texas petroleum fields

|+ {{table number|1}}Tentative, relative depositional heterogeneity ranking of reservoir facies based primarily on Texas [[petroleum]] fields

|-

|-

! Depositional Environment

! Depositional Environment

! Heterogeneity Rank

! Heterogeneity Rank

|-

|-

| ''' Siliciclastic Systems '''

| colspan=2 | ''' Siliciclastic Systems '''

 

|-

|-

|   Submarine slope/fan/canyon fill, silty to muddy

|   Submarine slope/fan/canyon fill, silty to muddy

| 8.0

| 8.0

|-

|-

|   Fluvial or deltaic sandstone on carbonate shelf

|   Fluvial or deltaic [[sandstone]] on carbonate shelf

| 8.0

| 8.0

|-

|-

| 2.0

| 2.0

|-

|-

| ''' Carbonate Systems '''

| colspan=2 | ''' Carbonate Systems '''

 

|-

|-

|   Evaporitic flats (sabkhas)

|   Evaporitic flats (sabkhas)

| 8.5

| 8.5

|-

|-

|   Open shelves, extensive diagenesis

|   Open shelves, extensive [[diagenesis]]

| 8.0

| 8.0

|-

|-

| 8.0

| 8.0

|-

|-

|   Karstic unconformity zones

|   Karstic [[unconformity]] zones

| 8.0

| 8.0

|-

|-

* Questionable correlation of depositional packages between wells

* Questionable correlation of depositional packages between wells

* Presence of numerous vertical [[permeability]] barriers at a variety of scales

* Presence of numerous vertical [[permeability]] barriers at a variety of scales

* Complex [[porosity]]-permeability and [[capillary pressure]] relationships (a broad scatter in the data indicates different lithofacies and pore types)

* Complex [[porosity]]-permeability and [[capillary pressure]] relationships (a broad scatter in the data indicates different [[lithofacies]] and pore types)

* Anomalous changes in pressure gradient

* Anomalous changes in pressure gradient

* Variable oil and water chemical composition

* Variable oil and water chemical composition

* Multiple [[fluid contacts]] at different structural elevations

* Multiple [[fluid contacts]] at different structural elevations

* Irregular reservoir distribution (such as a dry hole surrounded by producers)

* Irregular reservoir distribution (such as a [[dry hole]] surrounded by producers)

* Anomalous fluid relationships (such as a gas zone underlying an oil zone or an oil zone downdip of water)

* Anomalous fluid relationships (such as a gas zone underlying an oil zone or an oil zone downdip of water)

* Irregular and/or highly directional waterflood response

* Irregular and/or highly directional waterflood response

==Evaluation==

==Evaluation==

[[file:evaluating-stratigraphically-complex-fields_fig1.png|thumb|{{figure number|1}}Example of electrofacies map showing distribution of SP log patterns. (From Galloway and Cheng.<ref name=pt06r35>Galloway, W. E., Cheng, E. S. S., 1985, Reservoir facies architecture in a microtidal barrier system—Frio Formation, Texas Gulf Coast: The University of Texas Bureau of Economic Geology, Report of Investigations, v. 144, 36 p.</ref>)]]

[[file:evaluating-stratigraphically-complex-fields_fig1.png|thumb|300px|{{figure number|1}}Example of electrofacies map showing distribution of SP log patterns. (From Galloway and Cheng.<ref name=pt06r35>Galloway, W. E., Cheng, E. S. S., 1985, Reservoir facies architecture in a microtidal barrier system—Frio Formation, Texas Gulf Coast: The University of Texas Bureau of Economic Geology, Report of Investigations, v. 144, 36 p.</ref>)]]

Recognition and three-dimensional characterization of reservoir heterogeneity in a stratigraphically complex field requires a well-by-well analysis of the following:

Recognition and three-dimensional characterization of reservoir heterogeneity in a stratigraphically complex field requires a well-by-well analysis of the following:

* [[Introduction to geological methods]]

* [[Introduction to geological methods]]

* [[Lithofacies and environmental analysis of clastic depositional systems]]

* [[Lithofacies and environmental analysis of clastic depositional systems]]

* [[Subsurface maps]]

* [[Subsurface maps]]

* [[Flow units for reservoir characterization]]

* [[Flow units for reservoir characterization]]

* [[Effective pay determination]]

* [[Effective pay determination]]

* [[Multivariate data analysis]]

* [[Cross section]]

* [[Geological cross sections]]

* [[Evaluating structurally complex reservoirs]]

* [[Evaluating structurally complex reservoirs]]

* [[Conversion of well log data to subsurface stratigraphic and structural information]]

* [[Conversion of well log data to subsurface stratigraphic and structural information]]

* [[Evaluating tight gas reservoirs]]

* [[Evaluating tight gas reservoirs]]

* [[Reservoir quality]]

* [[Reservoir quality]]

* [[Carbonate reservoir models: facies, diagenesis, and flow characterization]]

* [[Carbonate reservoir models: facies, diagenesis, and flow characterization]]

* [[Evaluating fractured reservoirs]]

* [[Evaluating fractured reservoirs]]

* [[Evaluating diagenetically complex reservoirs]]

* [[Evaluating diagenetically complex reservoirs]]

==References==

==References==

[[Category:Geological methods]]

[[Category:Geological methods]]