Changes

==Plotting gradient==

==Plotting gradient==

The table below outlines the procedure for plotting a hydrocarbon pressure gradient on a hydrostatic pressure plot when a measured pressure is available from the [[reservoir]].

The list below outlines the procedure for plotting a hydrocarbon pressure gradient on a hydrostatic pressure plot when a measured pressure is available from the [[reservoir]].

# Plot measured fluid pressure on a hydrostatic pressure–depth plot.

# Determine the hydrocarbon pressure gradient from one of two ways:

#*  Measured hydrocarbon [[Wikipedia:Density|density]]  

#*  Estimates of hydrocarbon density

# Determine the [[buoyancy pressure]] gradient: [[Normal hydrostatic pressure gradients|static water pressure gradient]] minus hydrocarbon pressure gradient.

# Determine a pressure above or below the measured depth point. The table below lists the steps for determining this number.

| Plot measured fluid pressure on a hydrostatic pressure–depth plot.

## Pick a depth above or below the measured point.  

## Multiply the difference in depth by the buoyancy pressure gradient.  

## Add the number from step 2 to the measured pressure if the depth is deeper; subtract if shallower.

| Determine the hydrocarbon pressure gradient from one of two ways:

##*'''Example:''' Measured pressure at [[depth::7607 ft]] is [[pressure::3530 psi]] and buoyancy pressure gradient is 0.076 psi/ft. What is the hydrocarbon pressure at [[depth::7507 ft]]?

*  Measured hydrocarbon [[Wikipedia:Density|density]]  

##*'''Solution:'''

*  Estimates of hydrocarbon density

##** 7607 ft – 7507 ft = 100 ft

##** 100 ft × 0.076 psi/ft = 7.6 psi

##** Hydrocarbon pressure at [[depth::7507 ft]] = [[pressure::3530 psi]] – [[pressure::7.6 psi]] = [[pressure::3522.4 psi]]

| Determine the [[buoyancy pressure]] gradient: [[Normal hydrostatic pressure gradients|static water pressure gradient]] minus hydrocarbon pressure gradient.

# Plot the pressure number from step 4 on the pressure–depth plot and draw a line between this point and the measured pressure point. This line is the hydrocarbon pressure gradient.

| Determine a pressure above or below the measured depth point. The table below lists the steps for determining this number.

# Pick a depth above or below the measured point.  

# Multiply the difference in depth by the buoyancy pressure gradient.  

# Add the number from step 2 to the measured pressure if the depth is deeper; subtract if shallower.

 

'''Example:''' Measured pressure at [[depth::7607 ft]] is [[pressure::3530 psi]] and buoyancy pressure gradient is 0.076 psi/ft. What is the hydrocarbon pressure at [[depth::7507 ft]]?

 

'''Solution:'''

* 7607 ft – 7507 ft = 100 ft

* 100 ft × 0.076 psi/ft = 7.6 psi

* Hydrocarbon pressure at [[depth::7507 ft]] = [[pressure::3530 psi]] – [[pressure::7.6 psi]] = [[pressure::3522.4 psi]]

| Plot the pressure number from step 4 on the pressure–depth plot and draw a line between this point and the measured pressure point. This line is the hydrocarbon pressure gradient.

==See also==

==See also==