Difference between revisions of "Free water level determination using pressure"

Latest revision as of 17:54, 17 February 2022

The free water level occurs where buoyancy pressure is zero in the reservoir-aquifer system. It defines the downdip limits of an accumulation. Pressure data reliability affects the resolution; however, resolution improves when it is supplemented with other petrophysical information.

Procedure: using repeat formation tester (RFT) data[edit]

Figure 1 Easy method for determining free-water level (FWL) by projecting RFT pressure data downward from a reservoir to the aquifer.

An easy method for determining free water level (FWL) is projecting RFT pressure data downward from a reservoir to the aquifer. Figure 1 illustrates the procedure.

Procedure using a single measurement[edit]

The list below outlines the procedure for determining the free water level using a single pressure buildup point in the reservoir.

Determine buoyancy pressure (P_b ) at the depth of the measured pressure (P_m ) from the measured pressure:
- $P_{\rm {b}}=P_{\rm {m}}-P_{\rm {hydrostatic}}$
Determine buoyancy pressure gradient (P_bg ):
- $P_{\rm {bg}}=P_{\rm {hydrostatic\ pressure\ gradient}}-P_{\rm {hydrocarbon\ pressure\ gradient}}$
Calculate downdip length of hydrocarbon column (h):
- $h={\frac {P_{\rm {b}}}{P_{\rm {bg}}}}$

As an example, let's determine the downdip length of a 30°API oil column with the following givens:

P_m = pressure::3555 psi at depth::7611 ft
P_hydrostatic = 3525 psi
P_{hydrostatic pressure gradient} = 0.465 psi/ft
P_{hydrocarbon pressure gradient} = 0.38 psi/ft

Answer (tied back to steps above):

P_{\rm {b}}=P_{m}-P_{\rm {hydrostatic}}=3555-3525=30\ \mathrm {psi}

P_{\rm {hydrostatic\ pressure\ gradient}}-P_{\rm {hydrocarbon\ pressure\ gradient}}=0.465-0.38=0.085{\mbox{ psi/ft}}

h={\frac {P_{\rm {b}}}{P_{\rm {bg}}}}=30{\mbox{ psi}}\div 0.054{\mbox{ psi/ft}}=556{\mbox{ ft}}

Therefore, the free water level is at depth::8167 ft.

External links[edit]

find literature about
Free water level determination using pressure

@@ Line 6: / Line 6: @@
   | part    = Critical elements of the petroleum system
   | chapter = Formation fluid pressure and its application
-  | frompg  = 5-1
+  | frompg  = 5-27
-  | topg    = 5-64
+  | topg    = 5-28
   | author  = Edward A. Beaumont, Forrest Fiedler
   | link    = http://archives.datapages.com/data/specpubs/beaumont/ch05/ch05.htm
@@ Line 19: / Line 19: @@
 [[file:formation-fluid-pressure-and-its-application_fig5-12.png|400px|thumb|{{figure number|1}}Easy method for determining free-water level (FWL) by projecting RFT pressure data downward from a reservoir to the aquifer.]]
-An easy method for determining free water level (FWL) is projecting RFT pressure data downward from a reservoir to the aquifer. [[:file:formation-fluid-pressure-and-its-application_fig5-12.png|Figure 1]] illustrates the procedure.
+An easy method for determining free water level (FWL) is projecting [[Wireline formation testers|RFT]] pressure data downward from a reservoir to the aquifer. [[:file:formation-fluid-pressure-and-its-application_fig5-12.png|Figure 1]] illustrates the procedure.
 ==Procedure using a single measurement==
-The table below outlines the procedure for determining the free water level using a single [[Pressure_transient_testing#Pressure_drawdown_and_buildup_tests|pressure buildup]] point in the reservoir.
+The list below outlines the procedure for determining the free water level using a single [[Pressure_transient_testing#Pressure_drawdown_and_buildup_tests|pressure buildup]] point in the reservoir.
-{| class = "wikitable"
+# Determine [[buoyancy pressure]] (''P''<sub>b</sub> ) at the depth of the measured pressure (P<sub>m</sub> ) from the measured pressure:
-|-
+#*:<math>P_{\rm b} = P_{\rm m} - P_{\rm hydrostatic}</math>
-! Step
+# Determine buoyancy pressure gradient (''P''<sub>bg</sub> ):
-! Action
+#*:<math>P_{\rm bg} = P_{\rm hydrostatic\ pressure\ gradient} - P_{\rm hydrocarbon\ pressure\ gradient}</math>
-|-
+# Calculate downdip length of [[hydrocarbon column]] (''h''):
-| 1
+#*:<math>h = \frac{P_{\rm b}}{P_{\rm bg}}</math>
-| Determine [[buoyancy pressure]] (''P''<sub>b</sub> ) at the depth of the measured pressure (P<sub>m</sub> ) from the measured pressure:
-:<math>P_{\rm b} = P_{\rm m} - P_{\rm hydrostatic}</math>
-|-
-| 2
-| Determine buoyancy pressure gradient (''P''<sub>bg</sub> ):
-:<math>P_{\rm bg} = P_{\rm hydrostatic\ pressure\ gradient} - P_{\rm hydrocarbon\ pressure\ gradient}</math>
-|-
-| 3
-| Calculate downdip length of hydrocarbon column (''h''):
-:<math>h = \frac{P_{\rm b}}{P_{\rm bg}}</math>
-|}
 As an example, let's determine the downdip length of a 30°API oil column with the following givens:
@@ Line 78: / Line 61: @@
 [[Category:Critical elements of the petroleum system]]
 [[Category:Formation fluid pressure and its application]]
+[[Category:Treatise Handbook 3]]

Difference between revisions of "Free water level determination using pressure"

Latest revision as of 17:54, 17 February 2022

Contents

Procedure: using repeat formation tester (RFT) data[edit]

Procedure using a single measurement[edit]

See also[edit]

External links[edit]

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