Changes

  | part    = Critical elements of the petroleum system

  | part    = Critical elements of the petroleum system

  | chapter = Migration of petroleum

  | chapter = Migration of petroleum

  | frompg  = 7-1

  | frompg  = 7-13

  | topg    = 7-38

  | topg    = 7-14

  | author  = Martin D. Matthews

  | author  = Martin D. Matthews

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch07/ch07.htm

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch07/ch07.htm

  | isbn    = 0-89181-602-X

  | isbn    = 0-89181-602-X

}}

}}

Hydrocarbons dissolved in water occur as true solution and micellar solution. Both of these forms enable the hydrocarbons to move one molecule at a time and thus restrict movement minimally. The method of transport is either through direct transport by the water or by diffusion through the water. Reservoirs formed by this type of migration are limited to gas and light condensates. Solution transport is responsible for the loss of gas from many reservoirs and water-washing of oils.

Hydrocarbons dissolved in water occur as true solution and micellar solution. Both of these forms enable the hydrocarbons to move one molecule at a time and thus restrict movement minimally. The method of transport is either through direct transport by the water or by diffusion through the water. Reservoirs formed by this type of [[Hydrocarbon migration|migration]] are limited to gas and light condensates. Solution transport is responsible for the loss of gas from many reservoirs and water-washing of oils.

==True solution==

==True solution==

[[file:migration-of-petroleum_fig7-4.png|300px|thumb|{{figure number|1}}The aqueous solubility of normal alkanes and aromatics at 25&deg;C. After McAuliffe.<ref name=ch07r6>McAuliffe, C., D., 1980, [http://archives.datapages.com/data/specpubs/geochem1/data/a029/a029/0001/0050/0089.htm Oil and gas migration: chemical and physical constraints], in Roberts, W., H., Cordell, R., J., eds., AAPG Studies in Geology no. 10, p. 89–107.</ref>]]

[[file:migration-of-petroleum_fig7-4.png|300px|thumb|{{figure number|1}}The aqueous solubility of normal alkanes and aromatics at 25&deg;C. After McAuliffe.<ref name=ch07r6>McAuliffe, C. D., 1980, [http://archives.datapages.com/data/specpubs/geochem1/data/a029/a029/0001/0050/0089.htm Oil and gas migration: chemical and physical constraints], in W. H. Roberts, and R. J. Cordell, eds., AAPG Studies in Geology no. 10, p. 89–107.</ref>]]

True solution is a function of pressure, temperature, salinity, molecular weight, and mixtures of components present. The aqueous solubility of normal alkanes and aromatics at [[temperature::25&deg;C]] is shown in [[:file:migration-of-petroleum_fig7-4.png|Figure 1]].

True solution is a function of pressure, temperature, salinity, molecular weight, and mixtures of components present. The aqueous solubility of normal alkanes and aromatics at [[temperature::25&deg;C]] is shown in [[:file:migration-of-petroleum_fig7-4.png|Figure 1]].

==Migration by diffusion==

==Migration by diffusion==

Migration by diffusion of light hydrocarbons in a water-filled pore system is extremely slow. Diffusion conveys hydrocarbons from areas of high concentrations to areas of lower concentrations. It is dominantly a dispersive force and is generally responsible for the loss of hydrocarbons, not their accumulation.

[[Hydrocarbon migration|migration]] by diffusion of light hydrocarbons in a water-filled pore system is extremely slow. Diffusion conveys hydrocarbons from areas of high concentrations to areas of lower concentrations. It is dominantly a dispersive force and is generally responsible for the loss of hydrocarbons, not their accumulation.

==Diffusion time vs. distance==

==Diffusion time vs. distance==

==Diffusion in shale vs. Sand==

==Diffusion in shale vs. Sand==

In sampled beds, dissolved benzene and toluene can follow a diffusion gradient horizontally for miles in sands but be absent vertically in the over- and underlying sections. This observation suggests diffusion is not a practical transport mechanism in shale. However, even in sands for distances greater than 10-100 m, migration by diffusion is insignificant relative to bulk flow of oil or gas as separate phases.

In sampled beds, dissolved benzene and toluene can follow a diffusion gradient horizontally for miles in sands but be absent vertically in the over- and underlying sections. This observation suggests diffusion is not a practical transport mechanism in shale. However, even in sands for distances greater than 10-100 m, [[Hydrocarbon migration|migration]] by diffusion is insignificant relative to bulk flow of oil or gas as separate phases.

==Selective depletion by diffusion==

==Selective depletion by diffusion==

[[Category:Critical elements of the petroleum system]]  

[[Category:Critical elements of the petroleum system]]  

[[Category:Migration of petroleum]]

[[Category:Migration of petroleum]]