Changes

[[file:migration-of-petroleum_fig7-3.png|300px|thumb|{{figure number|1}}Comparison of shale pore size with hydrocarbon molecule size. From Momper;<ref name=Momper1978>Momper, J. A., 1978, [http://archives.datapages.com/data/specpubs/geochem1/data/a034b/a034/0001/0000/t1.htm Oil migration limitations suggested by geological and geochemical considerations], in W. H. Roberts and R. J. Cordel, eds., Physical and Chemical Constraints on Petroleum Migration: AAPG Continuing Education Course Notes Series no. 8, p. B1–B60.</ref> courtesy AAPG.]]

[[file:migration-of-petroleum_fig7-3.png|300px|thumb|{{figure number|1}}Comparison of shale pore size with hydrocarbon molecule size. From Momper;<ref name=Momper1978>Momper, J. A., 1978, [http://archives.datapages.com/data/specpubs/geochem1/data/a034b/a034/0001/0000/t1.htm Oil migration limitations suggested by geological and geochemical considerations], in W. H. Roberts and R. J. Cordel, eds., Physical and Chemical Constraints on Petroleum Migration: AAPG Continuing Education Course Notes Series no. 8, p. B1–B60.</ref> courtesy AAPG.]]

Shale pore sizes range over five orders of magnitude and are about the diameter of the individual hydrocarbon molecules. This suggests many pore throats will be able to pass only the smaller hydrocarbon molecules due to physical restrictions (styric effects). Thus, the larger shale pores are supplied with full-spectrum hydrocarbons migrating directly from kerogen in contact with the pores. Larger shale pores are also preferentially supplied with the smaller paraffin and aromatics from the neighboring smaller pores. [[:file:migration-of-petroleum_fig7-3.png|Figure 1]] compares shale pore size with hydrocarbon molecule size.

Shale pore sizes range over five orders of magnitude and are about the diameter of the individual hydrocarbon molecules. This suggests many pore throats will be able to pass only the smaller hydrocarbon molecules due to physical restrictions (styric effects). Thus, the larger shale pores are supplied with full-spectrum hydrocarbons migrating directly from [[kerogen]] in contact with the pores. Larger shale pores are also preferentially supplied with the smaller paraffin and aromatics from the neighboring smaller pores. [[:file:migration-of-petroleum_fig7-3.png|Figure 1]] compares shale pore size with hydrocarbon molecule size.

==Trapping large molecules in shale==

==Trapping large molecules in shale==

==Permeability==

==Permeability==

[[Permeability]] is related to pore throat size, distribution, and interconnectedness. It is a measurement of the rate at which fluids move through a pore system. The properties of the fluids present in the pores also control the rate at which they move through the system. [[Permeability]] is inversely related to the viscosity of the fluid moving through the pores. The presence of more than one immiscible phase in the pore system reduces the [[permeability]] of each phase below what it would be if it were the only phase present. Permeability measurements are dominantly taken in sands for reservoir engineering purposes and rarely in shales because of difficulties in getting good measurements. Also, permeabilities derived from cores are characteristically lower than those measured during production tests.

[[Permeability]] is related to pore throat size, distribution, and interconnectedness. It is a measurement of the rate at which fluids move through a pore system. The properties of the fluids present in the pores also control the rate at which they move through the system. [[Permeability]] is inversely related to the [[viscosity]] of the fluid moving through the pores. The presence of more than one immiscible phase in the pore system reduces the [[permeability]] of each phase below what it would be if it were the only phase present. Permeability measurements are dominantly taken in sands for reservoir engineering purposes and rarely in shales because of difficulties in getting good measurements. Also, permeabilities derived from cores are characteristically lower than those measured during production tests.

==Capillary forces==

==Capillary forces==

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

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

[[Category:Migration of petroleum]]

[[Category:Migration of petroleum]]