View source for Displacement pressure estimation from sedimentary facies and well logs

{{publication 
 | image   = exploring-for-oil-and-gas-traps.png
 | width   = 120px
 | series  = Treatise in Petroleum Geology
 | title   = Exploring for Oil and Gas Traps
 | part    = Predicting the occurrence of oil and gas traps
 | chapter = Evaluating top and fault seal
 | frompg  = 10-1
 | topg    = 10-94
 | author  = Grant M. Skerlec
 | link    = http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm
 | pdf     = 
 | store   = http://store.aapg.org/detail.aspx?id=545
 | isbn    = 0-89181-602-X
}}
[[Displacement pressure]] has been inferred from the relationship between capillary properties and [[Lithofacies|sedimentary facies]].<ref name=ch10r87>Vavra, C. L., J. G. Kaldi, and R. M. Sneider, 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., J. R. Schwalbach, and D. M. Allard, 1993, Integrated rock-log evaluation of fluvio-lacustrine seals, in J. Ebanks, J. Kaldi, and C. Vavra, eds., Seals and Traps: A Multidisciplinary Approach: AAPG Hedberg Research conference, unpublished abstract.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==

[[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 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<sup>o</sup> 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:_expected_value_and_chance_of_success#Probability_of_geological_success|risk]] was defined by combining P<sub>d</sub> with qualitative assessments of [[ductility]], [[Fracture|fracturing]], thickness, and [[lateral]] continuity.<ref name=ch10r87 />

==Example: onshore African basin==
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==
An encouraging development is the attempt to establish a relationship between log response and displacement pressure.<ref name=ch10r1>Alger, R. P., D. L. Luffel, and R. B. Truman, 1989, New unified method of integrating core capillary pressure data with well logs: Society of Petroleum Formation Evaluation, vol. 4, no. 2, p. 145–152, DOI: [https://www.onepetro.org/journal-paper/SPE-16793-PA 10.2118/16793-PA].</ref><ref name=ch10r68 /><ref name=ch10r78>Sneider, R. M., and G. Bolger, 1993, Estimating seals from wireline logs of clastic seals and reservoir intervals, in J. Ebanks, J. Kaldi, and C. Vavra, eds., Seals and Traps: A Multidisciplinary Approach: AAPG Hedberg Research conference, unpublished abstract.</ref><ref>Sneider, R. M., and J. Neasham, 1993, Comparison of seal capacity determination (SCD) from cores with SCD’s from cuttings of the same interval, in J. Ebanks, J. Kaldi, and C. Vavra, eds., Seals and Traps: A Multidisciplinary Approach: AAPG Hedberg Research Conference, unpublished abstract.</ref> [[Basic open hole tools#Resistivity|Resistivity logs]] directly reflect the relative proportions of clay minerals and organics to [[quartz]] and other minerals. Clay-rich seals with high displacement pressures have low resistivities. Clay-poor rocks with lower displacement pressures have high resistivities.<ref name=ch10r78 />

==See also==
* [[Measuring displacement pressure using mercury injection]]
* [[Estimating displacement pressure from pore size]]

==References==
{{reflist}}

==External links==
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[[Category:Predicting the occurrence of oil and gas traps]] 
[[Category:Evaluating top and fault seal]]
[[Category:Treatise Handbook 3]]