Changes

Eolian sands develop in arid settings and commonly form extensive, blanket-like deposits ([[:file:lithofacies-and-environmental-analysis-of-clastic-depositional-systems_fig3.png|Figure 3b]]). Wind transport removes fines and produces rounded and extremely [[Core_description#Maturity|well sorted]] grains often leading to favorable reservoir quality.

Eolian sands develop in arid settings and commonly form extensive, blanket-like deposits ([[:file:lithofacies-and-environmental-analysis-of-clastic-depositional-systems_fig3.png|Figure 3b]]). Wind transport removes fines and produces rounded and extremely [[Core_description#Maturity|well sorted]] grains often leading to favorable reservoir quality.

This combination of widespread occurrence and good reservoir properties makes eolian sandstones attractive exploration targets and many hydrocarbon accumulations have been discovered in such deposits.<ref name=pt06r2>Ahlbrandt, T. S., Fryberger, S. G., 1982, [http://archives.datapages.com/data/specpubs/sandsto2/data/a058/a058/0001/0000/0011.htm Introduction to eolian deposits], in Scholle, P. A., Spearing, D. eds., Sandstone Depositional Environments: [http://store.aapg.org/detail.aspx?id=627 AAPG Memoir 31], p. 11–47.</ref>

This combination of widespread occurrence and good reservoir properties makes eolian sandstones attractive exploration targets and many hydrocarbon accumulations have been discovered in such deposits.<ref name=pt06r2>Ahlbrandt, T. S., and S. G. Fryberger, 1982, [http://archives.datapages.com/data/specpubs/sandsto2/data/a058/a058/0001/0000/0011.htm Introduction to eolian deposits], in P. A. Scholle, and D. Spearing, eds., Sandstone Depositional Environments: [http://store.aapg.org/detail.aspx?id=627 AAPG Memoir 31], p. 11–47.</ref>

Eolian deposits include [[dune]], [[interdune]]  (marginal to dune complex), and [[extradune]] (noneolian) lateral deposits.<ref name=pt06r2 /> Dune deposits comprise the major sedimentary bodies in eolian successions. All are characterized by large scale [[cross-stratification]] in which [[foreset]] dips range up to 35°. Associated deposits may include those of [[wadi]] (fluvial), [[playa]] (lacustrine), and [[sabkha]] (arid tidal flat) origin.

Eolian deposits include [[dune]], [[interdune]]  (marginal to dune complex), and [[extradune]] (noneolian) lateral deposits.<ref name=pt06r2 /> Dune deposits comprise the major sedimentary bodies in eolian successions. All are characterized by large scale [[cross-stratification]] in which [[foreset]] dips range up to 35°. Associated deposits may include those of [[wadi]] (fluvial), [[playa]] (lacustrine), and [[sabkha]] (arid tidal flat) origin.

In the subsurface, eolian sandstones generally comprise thickly bedded sequences with few major interstratified shales. The sequences tend to be uniform and lack discernible coarsening- or fining-upward trends and, thus, exhibit blocky to weakly serrated [[Basic open hole tools#Gamma ray|gamma ray]], [[Basic open hole tools#Spontaneous potential|SP]], and [[Basic open hole tools#Resistivity|resistivity]] log profiles The well-bedded and high angle cross stratified nature of eolian sandstones promotes reliable results from [[Dipmeter analysis|dipmeter]] logs. Dune and interdune deposits can often be distinguished and paleowind directions inferred using correctly processed dipmeter data.<ref name=pt06r80>Lupe, R., Ahlbrandt, T. S., 1979, Sediments of the ancient eolian environment—reservoir inhomogeneity, in McKee, E., D., ed., A Study of Global Sand Seas: [http://pubs.er.usgs.gov/publication/pp1052 U.S. Geological Survey Professional Paper 1052], p. 241–252.</ref>

In the subsurface, eolian sandstones generally comprise thickly bedded sequences with few major interstratified shales. The sequences tend to be uniform and lack discernible coarsening- or fining-upward trends and, thus, exhibit blocky to weakly serrated [[Basic open hole tools#Gamma ray|gamma ray]], [[Basic open hole tools#Spontaneous potential|SP]], and [[Basic open hole tools#Resistivity|resistivity]] log profiles The well-bedded and high angle cross stratified nature of eolian sandstones promotes reliable results from [[Dipmeter analysis|dipmeter]] logs. Dune and interdune deposits can often be distinguished and paleowind directions inferred using correctly processed dipmeter data.<ref name=pt06r80>Lupe, R., and T. S. Ahlbrandt, 1979, Sediments of the ancient eolian environment—reservoir inhomogeneity, in E. D. McKee, ed., A Study of Global Sand Seas: [http://pubs.er.usgs.gov/publication/pp1052 U.S. Geological Survey Professional Paper 1052], p. 241–252.</ref>

Eolian sandstones generally comprise excellent reservoir intervals but often possess complex [[porosity]] and [[permeability]] variations. They are commonly anisotropic with regard to the flow of fluids and exhibit greater horizontal than vertical permeability because of their pronounced lamination.<ref name=pt06r154>Weber, K. J., 1987, Computation of initial well productivities in aeolian sandstone on the basis of a geological model, Leman Gas field, U., K., in Tillman, R. W., Weber, K. J., eds., Reservoir Sedimentology: [https://members.sepm.org/iMISpublic/Core/Orders/Default.aspx? SEPM Special Publication 40], p. 335–354.</ref>

Eolian sandstones generally comprise excellent reservoir intervals but often possess complex [[porosity]] and [[permeability]] variations. They are commonly anisotropic with regard to the flow of fluids and exhibit greater horizontal than vertical permeability because of their pronounced lamination.<ref name=pt06r154>Weber, K. J., 1987, Computation of initial well productivities in aeolian sandstone on the basis of a geological model, Leman Gas field, UK, in R. W. Tillman, and K. J. Weber, eds., Reservoir Sedimentology: [https://members.sepm.org/iMISpublic/Core/Orders/Default.aspx? SEPM Special Publication 40], p. 335–354.</ref>

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