Changes

  | part    = Predicting the occurrence of oil and gas traps

  | part    = Predicting the occurrence of oil and gas traps

  | chapter = Predicting reservoir system quality and performance

  | chapter = Predicting reservoir system quality and performance

  | frompg  = 9-1

  | frompg  = 9-46

  | topg    = 9-156

  | topg    = 9-47

  | author  = Dan J. Hartmann, Edward A. Beaumont

  | author  = Dan J. Hartmann, Edward A. Beaumont

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch09/ch09.htm

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch09/ch09.htm

==What is the Archie equation?==

==What is the Archie equation?==

Archie<ref name=ch09r2>Archie, G., E., 1952, [http://archives.datapages.com/data/bulletns/1949-52/data/pg/0036/0002/0250/0278.htm Classification of carbonate reservoir rocks and petrophysical considerations]: AAPG Bulletin, vol. 36, no. 2, p. 218–298. ''A classic paper written way before its time.''</ref> developed his famous equation to calculate, from well log parameters, the [[water saturation]] (S_w) of the uninvaded zone in a formation next to a borehole. The Archie equation can be expressed as follows:

Archie<ref name=ch09r2>Archie, G. E., 1952, [http://archives.datapages.com/data/bulletns/1949-52/data/pg/0036/0002/0250/0278.htm Classification of carbonate reservoir rocks and petrophysical considerations]: AAPG Bulletin, vol. 36, no. 2, p. 218–298. ''A classic paper written way before its time.''</ref> developed his famous equation to calculate, from well log parameters, the [[water saturation]] (S_w) of the uninvaded zone in a formation next to a borehole. The Archie equation can be expressed as follows:

:<math>\mbox{S}_{\rm w}{}^{\rm n} = \frac{\mbox{R}_{\rm w}}{(\Phi^{\rm m} \times \mbox{R}_{\rm t})}</math>

:<math>\mbox{S}_{\rm w}{}^{\rm n} = \frac{\mbox{R}_{\rm w}}{(\Phi^{\rm m} \times \mbox{R}_{\rm t})}</math>

{| class = "wikitable"

{| class = "wikitable"

|-

|-

! Step

! Step || Find || Use… || If… || Then…

! Find

! Use…

! If…

! Then…

|-

|-

| 1

| 1 || n

| n

|

|

*  2.0 for Archie porosity

*  2.0 for Archie porosity

*  1.8 (or less) for rocks with clayey matrix or fractures

*  1.8 (or less) for rocks with clayey matrix or [[fracture]]s

*  4.0 for very strongly oil-wet rocks

*  4.0 for very strongly [http://www.glossary.oilfield.slb.com/en/Terms/o/oil_wet.aspx oil-wet] rocks

| Not sure of rock type

| Not sure of rock type || Use 2.0

| Use 2.0

|-

|-

| 2

| 2 || R_w

| R_w

|

|

*  Value calculated from SP log  

*  Value calculated from [[Basic_open_hole_tools#Spontaneous_potential|spontaneous potential]] (SP) log  

*  Estimated from R_w catalogs  

*  Estimated from R_w catalogs  

*  Estimated from wet zone R_o value  

*  Estimated from wet zone R_o value  

*  Measured from water sample

*  Measured from water sample

| Thin beds, hydrocarbons in zone, or fresh formation waters make SP calculations uncertain

| Thin beds, hydrocarbons in zone, or fresh formation waters make SP calculations uncertain || Use [[thin-bed correction]] or another method

| Use thin-bed correction or another method

|-

|-

| 3

| 3 || Φ || Value derived from cores, density, density–neutron, or sonic logs (See [[Basic open hole tools]].) || Density–neutron log matrix setting does not match formation matrix || Use density– neutron crossplot (See [[Determining porosity from density-neutron logs]].)

| Φ

| Value derived from cores, density, density–neutron, or sonic logs

| Density–neutron log matrix setting does not match formation matrix

| Use density– neutron crossplot

|-

|-

| 4

| 4 || m

| m

|

|

*  2.0 for Archie porosity  

*  2.0 for Archie porosity  

*  1.7–2.0 for shaly sandstones  

*  1.7–2.0 for shaly sandstones  

*  2.0–2.5 for porosity with connected vugs  

*  2.0–2.5 for porosity with connected [http://www.merriam-webster.com/dictionary/vug vugs]

*  2.5–3.0 for nonconnected moldic porosity  

*  2.5–3.0 for nonconnected [[Porosity#Carbonate_pore_systems|moldic porosity]]

*  ~1.0 for fractured rocks

*  ~1.0 for fractured rocks

| Not sure of rock type or pore geometry

| Not sure of rock type or pore geometry || Use 2.0

| Use 2.0

|-

|-

| 5

| 5 || R_t || Value derived from deep resistivity log such as RILD or RLLD || Beds are thin, invasion occurred or borehole has washouts || Use chartbook corrections

| R_t

| Value derived from deep resistivity log such as RILD or RLLD

| Beds are thin, invasion occurred or borehole has washouts

| Use chartbook corrections

|}

|}

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Predicting reservoir system quality and performance]]

[[Category:Predicting reservoir system quality and performance]]