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Borehole gravity: uses, advantages, and disadvantages (view source)
Revision as of 22:12, 17 January 2014
, 22:12, 17 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 = Applying gravity in petroleum exploration
| frompg = 15-1
| topg = 15-28
| author = David A. Chapin, Mark E. Ander
| link = http://archives.datapages.com/data/specpubs/beaumont/ch15/ch15.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
==[[Borehole gravity]] uses==
Borehole gravity is especially effective for the following exploration and production purposes:
'''Exploration purposes'''
* Locating nearby salt structures
* Locating distance to nearby structures (e.g., reefs) for step-outs and sidetracks
* Better [[synthetic seismogram]]s
'''Production purposes'''
* Measuring bulk density when radioactive tools are too risky
* Logging cased holes for lithologic changes
* Calculating overburden for hydrofracture jobs
* Monitoring injection fluids
* Monitoring reservoirs during fluid withdrawal
* Exploring for bypassed, behind-casing gas zones
* Evaluating reservoir [[porosity]], especially in carbonate reservoirs where other tools are not as reliable
==Borehole gravity advantages==
The following characteristics give [[borehole gravity]] surveys advantages in certain situations:
* Directly measures bulk density
* Is a deep imaging tool
* Is effective in both cased and uncased wells
* Is unaffected by washouts, hole rugosity, or mud invasion effects
* Can help determine seismic wavelet scale density
* Is a passive measurement, e.g., does not have active radioactive sources
==Borehole gravity disadvantages==
The following characteristics give borehole gravity surveys disadvantages in certain situations:
* Direction away from the well to distant source cannot be determined without other information
* Engineering limitations of the tool restricts use to certain candidate wells (hole size, low deviation, slow reading)
* Only a few tools presently available for use
* Expensive to operate
==Theory==
Density effects caused by downhole geology can be detected by very sensitive instrumentation and by knowing precisely where the sensor is located in the borehole. For petroleum exploration, gravity typically is measured in microgals (μGal). Typical exploration anomalies are on the order of
==See also==
* [[Applying borehole gravity methods]]
* [[The borehole gravity tool]]
* [[Examples of borehole gravity applications]]
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch15/ch15.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:Applying gravity in petroleum exploration]]
| 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 = Applying gravity in petroleum exploration
| frompg = 15-1
| topg = 15-28
| author = David A. Chapin, Mark E. Ander
| link = http://archives.datapages.com/data/specpubs/beaumont/ch15/ch15.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
==[[Borehole gravity]] uses==
Borehole gravity is especially effective for the following exploration and production purposes:
'''Exploration purposes'''
* Locating nearby salt structures
* Locating distance to nearby structures (e.g., reefs) for step-outs and sidetracks
* Better [[synthetic seismogram]]s
'''Production purposes'''
* Measuring bulk density when radioactive tools are too risky
* Logging cased holes for lithologic changes
* Calculating overburden for hydrofracture jobs
* Monitoring injection fluids
* Monitoring reservoirs during fluid withdrawal
* Exploring for bypassed, behind-casing gas zones
* Evaluating reservoir [[porosity]], especially in carbonate reservoirs where other tools are not as reliable
==Borehole gravity advantages==
The following characteristics give [[borehole gravity]] surveys advantages in certain situations:
* Directly measures bulk density
* Is a deep imaging tool
* Is effective in both cased and uncased wells
* Is unaffected by washouts, hole rugosity, or mud invasion effects
* Can help determine seismic wavelet scale density
* Is a passive measurement, e.g., does not have active radioactive sources
==Borehole gravity disadvantages==
The following characteristics give borehole gravity surveys disadvantages in certain situations:
* Direction away from the well to distant source cannot be determined without other information
* Engineering limitations of the tool restricts use to certain candidate wells (hole size, low deviation, slow reading)
* Only a few tools presently available for use
* Expensive to operate
==Theory==
Density effects caused by downhole geology can be detected by very sensitive instrumentation and by knowing precisely where the sensor is located in the borehole. For petroleum exploration, gravity typically is measured in microgals (μGal). Typical exploration anomalies are on the order of
==See also==
* [[Applying borehole gravity methods]]
* [[The borehole gravity tool]]
* [[Examples of borehole gravity applications]]
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch15/ch15.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:Applying gravity in petroleum exploration]]