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A single-point test for [[Deliverability testing of gas wells|gas well deliverability]] is an attempt to overcome the limitation of long test times required for [[Flow-after-flow tests for gas wells|flow-after-flow tests]]. This article discusses the implementation and analysis of single-point testing for gas-well deliverability tests. Both the Rawlins and Schellhardt and Houpeurt analysis techniques are presented in terms of pseudopressures.  
A single-point test for [[Deliverability_testing_of_gas_wells|gas well deliverability]] is an attempt to overcome the limitation of long test times required for [[Flow-after-flow_tests_for_gas_wells|flow-after-flow tests]]. This article discusses the implementation and analysis of single-point testing for gas-well deliverability tests. Both the Rawlins and Schellhardt and Houpeurt analysis techniques are presented in terms of pseudopressures.


==Single-point test procedure and analysis==
== Single-point test procedure and analysis ==
A single-point test is conducted by flowing the well at a single rate until the sandface pressure is stabilized. One limitation of this test is that it requires prior knowledge of the well’s deliverability behavior, either from previous well tests or possibly from correlations with other wells producing in the same field under similar conditions. Ensure that the well has flowed long enough to be out of wellbore storage and in the boundary-dominated or stabilized flow regime. Similarly, for hydraulically fractured wells, the well must be flowed long enough to be in the pseudoradial flow regime and then stabilized.


To analyze a single-point test with the Rawlins-Schellhardt method, ''n'' must be known or estimated. An estimate of ''n'' can be obtained either from a previous deliverability test on the well or from correlations with similar wells producing from the same formation under similar conditions. The calculation procedure is similar to that presented for flow-after-flow tests. The [[Glossary:Absolute open flow|absolute open flow]] (AOF) can be estimated graphically by drawing a straight line through the single flow point with a slope of 1/''n'' and extrapolating it to the flow rate at [[File:Vol5 page 0851 inline 001.png]]. The AOF can also be calculated with
A single-point test is conducted by flowing the well at a single rate until the sandface pressure is stabilized. One limitation of this test is that it requires prior knowledge of the well’s deliverability behavior, either from previous well tests or possibly from correlations with other wells producing in the same field under similar conditions. Ensure that the well has flowed long enough to be out of wellbore storage and in the boundary-dominated or stabilized flow regime. Similarly, for hydraulically fractured wells, the well must be flowed long enough to be in the pseudoradial flow regime and then stabilized.


[[File:Vol5 page 0851 eq 001.png]]
To analyze a single-point test with the Rawlins-Schellhardt method, ''n'' must be known or estimated. An estimate of ''n'' can be obtained either from a previous deliverability test on the well or from correlations with similar wells producing from the same formation under similar conditions. The calculation procedure is similar to that presented for flow-after-flow tests. The [[Glossary:Absolute_open_flow|absolute open flow]] (AOF) can be estimated graphically by drawing a straight line through the single flow point with a slope of 1/''n'' and extrapolating it to the flow rate at [[File:Vol5 page 0851 inline 001.png|RTENOTITLE]]. The AOF can also be calculated with
 
[[File:Vol5 page 0851 eq 001.png|RTENOTITLE]]


where ''C'' is estimated with
where ''C'' is estimated with


[[File:Vol5 page 0851 eq 002.png]]
[[File:Vol5 page 0851 eq 002.png|RTENOTITLE]]


To use the Houpeurt analysis technique, the slope, ''b'', of the line on a plot of
To use the Houpeurt analysis technique, the slope, ''b'', of the line on a plot of


[[File:Vol5 page 0851 eq 003.png]]
[[File:Vol5 page 0851 eq 003.png|RTENOTITLE]]


must be known. If a value of ''b'' is unavailable, estimate ''b'' using '''Eq. 1'''. Note that estimates of the formation properties are necessary to use '''Eq. 1'''. The remaining analysis procedure is similar to that for flow-after-flow tests.  
must be known. If a value of ''b'' is unavailable, estimate ''b'' using '''Eq. 1'''. Note that estimates of the formation properties are necessary to use '''Eq. 1'''. The remaining analysis procedure is similar to that for flow-after-flow tests.


[[File:Vol5 page 0841 eq 007.png]]....................(1)
[[File:Vol5 page 0841 eq 007.png|RTENOTITLE]]....................(1)


== Nomenclature ==
== Nomenclature ==
{|
{|
|''b''
|=
|[[File:Vol5 page 0880 inline 001.png]] (gas flow equation)
|-
|-
|''C''  
| ''b''
|=  
| =
|performance coefficient in gas-well deliverability equation, or wellbore storage coefficient, bbl/psi  
| [[File:Vol5 page 0880 inline 001.png|RTENOTITLE]] (gas flow equation)
|-
| ''C''
| =
| performance coefficient in gas-well deliverability equation, or wellbore storage coefficient, bbl/psi
|-
|-
|''D''  
| ''D''
|=  
| =
|non-Darcy flow constant, D/Mscf  
| non-Darcy flow constant, D/Mscf
|-
|-
|''h''  
| ''h''
|=  
| =
|net formation thickness, ft  
| net formation thickness, ft
|-
|-
|''k''<sub>''g''</sub>  
| ''k''<sub>''g''</sub>
|=  
| =
|permeability to gas, md  
| permeability to gas, md
|-
|-
|''p''<sub>''p''</sub>  
| ''p''<sub>''p''</sub>
|=  
| =
|pseudopressure, psia<sup>2</sup>/cp  
| pseudopressure, psia<sup>2</sup>/cp
|-
|-
|[[File:Vol5 page 0781 inline 001.png]]  
| [[File:Vol5 page 0781 inline 001.png|RTENOTITLE]]
|=  
| =
|volumetric average or static drainage-area pressure, psi  
| volumetric average or static drainage-area pressure, psi
|-
|-
|''p''<sub>''wf''</sub>  
| ''p''<sub>''wf''</sub>
|=  
| =
|flowing BHP, psi  
| flowing BHP, psi
|-
|-
|''q''  
| ''q''
|=  
| =
|flow rate at surface, STB/D  
| flow rate at surface, STB/D
|-
|-
|''q''<sub>AOF</sub>  
| ''q''<sub>AOF</sub>
|=  
| =
|absolute-open-flow potential, MMscf/D  
| absolute-open-flow potential, MMscf/D
|-
|-
|''T''  
| ''T''
|=  
| =
|reservoir temperature, °R  
| reservoir temperature, °R
|-
|-
|Δ''p''<sub>''p''</sub>  
| Δ''p''<sub>''p''</sub>
|=  
| =
|pseudopressure change since start of test, psia<sup>2</sup>/cp  
| pseudopressure change since start of test, psia<sup>2</sup>/cp
|}
|}


==Noteworthy papers in OnePetro==
== Noteworthy papers in OnePetro ==
 
Use this section to list papers in OnePetro that a reader who wants to learn more should definitely read
Use this section to list papers in OnePetro that a reader who wants to learn more should definitely read


==External links==
== External links ==
 
Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro
Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro


==See also==
== See also ==
[[Deliverability testing of gas wells]]
 
[[Deliverability_testing_of_gas_wells|Deliverability testing of gas wells]]
 
[[Flow-after-flow_tests_for_gas_wells|Flow-after-flow tests for gas wells]]
 
[[Isochronal_tests_for_gas_wells|Isochronal tests for gas wells]]


[[Flow-after-flow tests for gas wells]]
[[Modified_isochronal_tests_for_gas_wells|Modified isochronal tests for gas wells]]


[[Isochronal tests for gas wells]]
[[Flow_equations_for_gas_and_multiphase_flow|Flow equations for gas and multiphase flow]]


[[Modified isochronal tests for gas wells]]
[[PEH:Fluid_Flow_Through_Permeable_Media]]


[[Flow equations for gas and multiphase flow]]
==Category==


[[PEH:Fluid Flow Through Permeable Media]]
[[Category:5.6.4 Drillstem or well testing]] [[Category:NR]]

Latest revision as of 13:07, 6 July 2015

A single-point test for gas well deliverability is an attempt to overcome the limitation of long test times required for flow-after-flow tests. This article discusses the implementation and analysis of single-point testing for gas-well deliverability tests. Both the Rawlins and Schellhardt and Houpeurt analysis techniques are presented in terms of pseudopressures.

Single-point test procedure and analysis

A single-point test is conducted by flowing the well at a single rate until the sandface pressure is stabilized. One limitation of this test is that it requires prior knowledge of the well’s deliverability behavior, either from previous well tests or possibly from correlations with other wells producing in the same field under similar conditions. Ensure that the well has flowed long enough to be out of wellbore storage and in the boundary-dominated or stabilized flow regime. Similarly, for hydraulically fractured wells, the well must be flowed long enough to be in the pseudoradial flow regime and then stabilized.

To analyze a single-point test with the Rawlins-Schellhardt method, n must be known or estimated. An estimate of n can be obtained either from a previous deliverability test on the well or from correlations with similar wells producing from the same formation under similar conditions. The calculation procedure is similar to that presented for flow-after-flow tests. The absolute open flow (AOF) can be estimated graphically by drawing a straight line through the single flow point with a slope of 1/n and extrapolating it to the flow rate at RTENOTITLE. The AOF can also be calculated with

RTENOTITLE

where C is estimated with

RTENOTITLE

To use the Houpeurt analysis technique, the slope, b, of the line on a plot of

RTENOTITLE

must be known. If a value of b is unavailable, estimate b using Eq. 1. Note that estimates of the formation properties are necessary to use Eq. 1. The remaining analysis procedure is similar to that for flow-after-flow tests.

RTENOTITLE....................(1)

Nomenclature

b = RTENOTITLE (gas flow equation)
C = performance coefficient in gas-well deliverability equation, or wellbore storage coefficient, bbl/psi
D = non-Darcy flow constant, D/Mscf
h = net formation thickness, ft
kg = permeability to gas, md
pp = pseudopressure, psia2/cp
RTENOTITLE = volumetric average or static drainage-area pressure, psi
pwf = flowing BHP, psi
q = flow rate at surface, STB/D
qAOF = absolute-open-flow potential, MMscf/D
T = reservoir temperature, °R
Δpp = pseudopressure change since start of test, psia2/cp

Noteworthy papers in OnePetro

Use this section to list papers in OnePetro that a reader who wants to learn more should definitely read

External links

Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro

See also

Deliverability testing of gas wells

Flow-after-flow tests for gas wells

Isochronal tests for gas wells

Modified isochronal tests for gas wells

Flow equations for gas and multiphase flow

PEH:Fluid_Flow_Through_Permeable_Media

Category