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Fault control on hydrocarbon distribution (view source)
Revision as of 14:10, 31 January 2014
, 14:10, 31 January 2014Initial import
{{publication
| image = exploring-for-oil-and-gas-traps.png
| width = 120px
| series = Treatise in Petroleum Geology
| title = Exploring for Oil and Gas Traps
| part = Predicting the occurrence of oil and gas traps
| chapter = Evaluating top and fault seal
| frompg = 10-1
| topg = 10-94
| author = Grant M. Skerlec
| link = http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
Faults control both the vertical and lateral distribution of hydrocarbons within fields. Some compartments and sands are dry; others contain subeconomic accumulations. Risking percent fill using fault seal analysis helps avoid needless wells.
==Distribution example==
The following figure is an example of faults controlling the distribution of hydrocarbons within a Gulf Coast field. The field contains 33 separate reservoir sands. At each mapped reservoir level, the field is divided into three major compartments (A, B, D) by faults. Compartment D is almost always empty, while the other compartments commonly contain hydrocarbons. In only 5 of the 33 reservoirs does Compartment D contain hydrocarbons.
Compartment D is commonly empty because a series of JLLPs along the western portion of Fault A allows hydrocarbons to leak into Compartment B and then across the eastern portion of Fault A into the next highest reservoir. Only when Fault Ais cross sealing does Compartment D contain hydrocarbons. Cross seal is created by shale-prone gouge with low SGRs or sand/shale juxtaposition.
[[file:evaluating-top-and-fault-seal_fig10-33.png|thumb|{{figure number|10-33}}See text for explanation.]]
==Assessing percent fill==
Despite numerous examples of this type, we often erroneously assign an equal chance of some specific percent fill when assessing a prospect's reservoirs and fault compartments. We must understand the following:
* All reservoirs in a series of stacked sands do not have the same chance of being filled with hydrocarbons.
* Each fault compartment of a single reservoir does not have the same chance of being filled with hydrocarbons.
* We can predict (predrill) which sands and fault compartments contain hydrocarbons and which are dry.
==Communication of fluids across faults==
Understanding communication of fluids across faults lets us develop fields more efficiently. Routine fault seal analysis during production avoids needless wells and helps us position necessary infill wells for producing residual accumulations. Cross-sealing faults compartmentalize a reservoir. Isolated compartments created by cross-sealing faults require individual production wells. In contrast, cross-leaking faults allow some fault-bounded compartments to be produced from adjacent compartments and additional wells may be unnecessary.
==See also==
* [[How faults affect field development]]
* [[Reservoir simulations and field unitization]]
* [[Fault seal breakdown during production]]
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm Original content in Datapages]
* [http://store.aapg.org/detail.aspx?id=545 Find the book in the AAPG Store]
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Evaluating top and fault seal]]
| image = exploring-for-oil-and-gas-traps.png
| width = 120px
| series = Treatise in Petroleum Geology
| title = Exploring for Oil and Gas Traps
| part = Predicting the occurrence of oil and gas traps
| chapter = Evaluating top and fault seal
| frompg = 10-1
| topg = 10-94
| author = Grant M. Skerlec
| link = http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
Faults control both the vertical and lateral distribution of hydrocarbons within fields. Some compartments and sands are dry; others contain subeconomic accumulations. Risking percent fill using fault seal analysis helps avoid needless wells.
==Distribution example==
The following figure is an example of faults controlling the distribution of hydrocarbons within a Gulf Coast field. The field contains 33 separate reservoir sands. At each mapped reservoir level, the field is divided into three major compartments (A, B, D) by faults. Compartment D is almost always empty, while the other compartments commonly contain hydrocarbons. In only 5 of the 33 reservoirs does Compartment D contain hydrocarbons.
Compartment D is commonly empty because a series of JLLPs along the western portion of Fault A allows hydrocarbons to leak into Compartment B and then across the eastern portion of Fault A into the next highest reservoir. Only when Fault Ais cross sealing does Compartment D contain hydrocarbons. Cross seal is created by shale-prone gouge with low SGRs or sand/shale juxtaposition.
[[file:evaluating-top-and-fault-seal_fig10-33.png|thumb|{{figure number|10-33}}See text for explanation.]]
==Assessing percent fill==
Despite numerous examples of this type, we often erroneously assign an equal chance of some specific percent fill when assessing a prospect's reservoirs and fault compartments. We must understand the following:
* All reservoirs in a series of stacked sands do not have the same chance of being filled with hydrocarbons.
* Each fault compartment of a single reservoir does not have the same chance of being filled with hydrocarbons.
* We can predict (predrill) which sands and fault compartments contain hydrocarbons and which are dry.
==Communication of fluids across faults==
Understanding communication of fluids across faults lets us develop fields more efficiently. Routine fault seal analysis during production avoids needless wells and helps us position necessary infill wells for producing residual accumulations. Cross-sealing faults compartmentalize a reservoir. Isolated compartments created by cross-sealing faults require individual production wells. In contrast, cross-leaking faults allow some fault-bounded compartments to be produced from adjacent compartments and additional wells may be unnecessary.
==See also==
* [[How faults affect field development]]
* [[Reservoir simulations and field unitization]]
* [[Fault seal breakdown during production]]
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm Original content in Datapages]
* [http://store.aapg.org/detail.aspx?id=545 Find the book in the AAPG Store]
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Evaluating top and fault seal]]