Difference between revisions of "Buoyancy pressures and hydrocarbon presence"
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Two items are critical for detecting buoyancy pressure in a well: | Two items are critical for detecting buoyancy pressure in a well: | ||
| − | * Accurate static water plot for the well | + | * Accurate static water plot for the well (See [[Constructing a hydrostatic pressure-depth plot]]) |
* Reliable formation fluid pressure measurements (See [[Methods for obtaining formation fluid pressures]]) | * Reliable formation fluid pressure measurements (See [[Methods for obtaining formation fluid pressures]]) | ||
==Procedure== | ==Procedure== | ||
| − | The | + | The list below outlines a procedure for using pressures to detect the presence of a hydrocarbon column in a formation. |
| − | + | # Make a [[Plotting the hydrocarbon pressure gradient|hydrostatic pressure-depth plot]] through the interval of interest. | |
| − | + | # Plot the pressure(s) measured from the interval of interest. | |
| − | + | # If the measured formation pressures are greater than the hydrostatic pressure, then the formation may contain a hydrocarbon column. | |
| − | + | # Check to see if anomalous pressures make geological sense. | |
| − | + | #* ''' Example: ''' Measured fluid pressure is [[pressure::250 psi]] over the static water pressure. The formation is believed to contain 30°API [[oil gravity|gravity oil]], and the total vertical trap closure is [[length::500 ft]]. | |
| − | + | #* ''' Solution: ''' If the 250-psi pressure is due to the presence of a hydrocarbon column, then a column of [[depth::2500 ft]] of 30°API [[gravity]] oil would have to be present in the trap (assuming a [[Constructing a hydrostatic pressure-depth plot#Rules of thumb|freshwater gradient]]). Vertical trap [[closure]] is only [[length::500 ft]]; therefore, the measured formation pressure does not match the geology and is probably wrong. | |
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| − | * ''' Example: ''' Measured fluid pressure is [[pressure::250 psi]] over the static water pressure. The formation is believed to contain 30°API [[oil gravity|gravity]] | ||
| − | * ''' Solution: ''' If the 250-psi pressure is due to the presence of a hydrocarbon column, then a column of [[depth::2500 ft]] of 30°API gravity oil would have to be present in the trap (assuming a freshwater gradient). Vertical trap closure is only [[length::500 ft]]; therefore, the measured formation pressure does not match the geology and is probably wrong. | ||
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==See also== | ==See also== | ||
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* [[Static hydrocarbon pressure gradients]] | * [[Static hydrocarbon pressure gradients]] | ||
* [[Methods for obtaining formation fluid pressures]] | * [[Methods for obtaining formation fluid pressures]] | ||
| − | * [[ | + | * [[Hydrostatic pressure-depth plot construction]] |
| + | * [[Plotting the hydrocarbon pressure gradient]] | ||
==External links== | ==External links== | ||
| Line 57: | Line 45: | ||
[[Category:Critical elements of the petroleum system]] | [[Category:Critical elements of the petroleum system]] | ||
[[Category:Formation fluid pressure and its application]] | [[Category:Formation fluid pressure and its application]] | ||
| + | [[Category:Treatise Handbook 3]] | ||
Latest revision as of 18:56, 16 February 2022
| Exploring for Oil and Gas Traps | |
| |
| Series | Treatise in Petroleum Geology |
|---|---|
| Part | Critical elements of the petroleum system |
| Chapter | Formation fluid pressure and its application |
| Author | Edward A. Beaumont, Forrest Fiedler |
| Link | Web page |
| Store | AAPG Store |
Buoyancy pressures caused by hydrocarbon columns can be recognized by comparing hydrostatic pressure gradients with formation pressures. Pressures exceeding expected hydrostatic pressures could be due to the presence of hydrocarbon columns.
Two items are critical for detecting buoyancy pressure in a well:
- Accurate static water plot for the well (See Constructing a hydrostatic pressure-depth plot)
- Reliable formation fluid pressure measurements (See Methods for obtaining formation fluid pressures)
Procedure[edit]
The list below outlines a procedure for using pressures to detect the presence of a hydrocarbon column in a formation.
- Make a hydrostatic pressure-depth plot through the interval of interest.
- Plot the pressure(s) measured from the interval of interest.
- If the measured formation pressures are greater than the hydrostatic pressure, then the formation may contain a hydrocarbon column.
- Check to see if anomalous pressures make geological sense.
- Example: Measured fluid pressure is pressure::250 psi over the static water pressure. The formation is believed to contain 30°API gravity oil, and the total vertical trap closure is length::500 ft.
- Solution: If the 250-psi pressure is due to the presence of a hydrocarbon column, then a column of depth::2500 ft of 30°API gravity oil would have to be present in the trap (assuming a freshwater gradient). Vertical trap closure is only length::500 ft; therefore, the measured formation pressure does not match the geology and is probably wrong.
See also[edit]
- Determining hydrostatic pressure gradient
- Static hydrocarbon pressure gradients
- Methods for obtaining formation fluid pressures
- Hydrostatic pressure-depth plot construction
- Plotting the hydrocarbon pressure gradient
External links[edit]
| find literature about Buoyancy pressures and hydrocarbon presence |
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