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Displacement pressure has been inferred from the relationship between capillary properties and sedimentary facies.<ref name=ch10r87>Vavra, C., L., Kaldi, J., G., Sneider, R., M., 1992, [http://archives.datapages.com/data/bulletns/1992-93/data/pg/0076/0006/0000/0840.htm Geological applications of capillary pressure: a review]: AAPG Bulletin, vol. 76, no. 6, p. 840–850.</ref><ref name=ch10r68>Shea, W., T., Schwalbach, J., R., Allard, D., M., 1993, Integrated rock-log evaluation of fluvio-lacustrine seals, in Ebanks, J., Kaldi, J., Vavra, C., eds., Seals and Traps: A Multidisciplinary Approach: AAPG Hedberg Research conference, unpublished abstract.</ref> Two examples demonstrate the ability to construct regional facies maps and then assign maximum limits to the amount of hydrocarbon that could be trapped beneath these seals.

[[Displacement pressure]] has been inferred from the relationship between capillary properties and [[Lithofacies|sedimentary facies]].<ref name=ch10r87>Vavra, C., L., Kaldi, J., G., Sneider, R., M., 1992, [http://archives.datapages.com/data/bulletns/1992-93/data/pg/0076/0006/0000/0840.htm Geological applications of capillary pressure: a review]: AAPG Bulletin, vol. 76, no. 6, p. 840–850.</ref><ref name=ch10r68>Shea, W., T., Schwalbach, J., R., Allard, D., M., 1993, Integrated rock-log evaluation of fluvio-lacustrine seals, in Ebanks, J., Kaldi, J., Vavra, C., eds., Seals and Traps: A Multidisciplinary Approach: AAPG Hedberg Research conference, unpublished abstract.</ref> Two examples demonstrate the ability to construct regional [[facies map]]s and then assign maximum limits to the amount of [[hydrocarbon]] that could be trapped beneath these [[seal]]s.

==Example: Ardjuna basin, Indonesia==

==Example: Ardjuna basin, Indonesia==

[[file:evaluating-top-and-fault-seal_fig10-49.png|300px|thumb|{{figure number|1}}Range of seal capacities for the different facies. Data from Vavra et al.<ref name=ch10r87 />]]

[[file:evaluating-top-and-fault-seal_fig10-49.png|300px|thumb|{{figure number|1}}Range of seal capacities for the different facies. Data from Vavra et al.<ref name=ch10r87 />]]

The top seal and capillary properties of rocks from the Ardjuna basin (offshore Java, Indonesia) are related to mappable facies.<ref name=ch10r87 /> The Talang Akar Formation consists of deltaic facies ranging from channel sandstones, delta plain shales, and channel abandonment siltstones to prodelta and delta-front shales as well as shelfal carbonates.

The top seal and capillary properties of rocks from the Ardjuna basin (offshore Java, Indonesia) are related to mappable facies.<ref name=ch10r87 /> The Talang Akar Formation consists of [[Deltaic environments|deltaic facies]] ranging from channel sandstones, delta plain shales, and channel abandonment siltstones to prodelta and delta-front shales as well as shelfal carbonates.

Each of these facies has a distinct range of displacement pressures. [[:file:evaluating-top-and-fault-seal_fig10-49.png|Figure 1]] shows the range of seal capacities for the different facies. Shelfal carbonates and delta-front shales are excellent seals, with displacement pressures > 1000 psia (air-mercury) and capable of trapping approximately 1000–10,000 ft of oil. Delta-plain shales are relatively poor seals, with displacement pressures of 80–90 psia (air-mercury^o and capable of trapping only 90–100 ft of oil.

Each of these facies has a distinct range of displacement pressures. [[:file:evaluating-top-and-fault-seal_fig10-49.png|Figure 1]] shows the range of seal capacities for the different facies. Shelfal carbonates and delta-front shales are excellent seals, with displacement pressures > 1000 psia (air-mercury) and capable of trapping approximately 1000–10,000 ft of oil. Delta-plain shales are relatively poor seals, with displacement pressures of 80–90 psia (air-mercury^o and capable of trapping only 90–100 ft of oil.

These values place an upper limit on the amount of hydrocarbon that can be trapped. Other factors, however, limit the sealing potential of these seals. Seal risk was defined by combining P_d with qualitative assessments of [[ductility]], fracturing, thickness, and lateral continuity.<ref name=ch10r87 />

These values place an upper limit on the amount of hydrocarbon that can be trapped. Other factors, however, limit the sealing potential of these seals. Seal [[Risk:_expected_value_and_chance_of_success#Probability_of_geological_success|risk]] was defined by combining P_d with qualitative assessments of [[ductility]], [[Fracture|fracturing]], thickness, and lateral continuity.<ref name=ch10r87 />

==Example: onshore African basin==

==Example: onshore African basin==

A study of an African basin found differences in displacement pressure among flood plain, lacustrine, and overbank facies.<ref name=ch10r68 /> Flood plain mudstones have displacement pressures of [[pressure::1,500 psi]] (air–mercury) and can trap more than [[length::300 m]] [[depth::(1,000 ft]]) of oil. Lacustrine and overbank facies contain some siltstones that have displacement pressures of [[pressure::500 psi]] (air–mercury) or less. These seal–rock facies can be correlated among wells and used to predict lateral facies variations and seal distribution in uncored wells.

A study of an African basin found differences in displacement pressure among flood plain, [http://www.merriam-webster.com/dictionary/lacustrine lacustrine], and overbank facies.<ref name=ch10r68 /> Flood plain mudstones have displacement pressures of [[pressure::1,500 psi]] (air–mercury) and can trap more than [[length::300 m]] [[depth::(1,000 ft]]) of oil. Lacustrine and overbank facies contain some [[siltstone]]s that have displacement pressures of [[pressure::500 psi]] (air–mercury) or less. These seal–rock facies can be correlated among wells and used to predict lateral facies variations and seal distribution in uncored wells.

==Recent developments==

==Recent developments==