Changes

==Procedure==

==Procedure==

The table below outlines a procedure for using pressures to detect the presence of a hydrocarbon column in a formation.

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.

| 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.

==See also==

==See also==

* [[Static hydrocarbon pressure gradients]]

* [[Static hydrocarbon pressure gradients]]

* [[Methods for obtaining formation fluid pressures]]

* [[Methods for obtaining formation fluid pressures]]

* [[Constructing a hydrostatic pressure-depth plot]]

* [[Hydrostatic pressure-depth plot construction]]

* [[Plotting the hydrocarbon pressure gradient]]

* [[Plotting the hydrocarbon pressure gradient]]

[[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]]