Changes

==Extrapolating true pressures==

==Extrapolating true pressures==

[[file:formation-fluid-pressure-and-its-application_fig5-15.png|thumb|{{figure number|3}}Example of how pressure is extrapolated from ISIP and FSIP on a Horner plot (pressure vs. psuedo or Horner time, or (T + ΔT)/ΔT. Copyright: Dahlberg;<ref name=ch05r5 /> courtesy Springer-Verlag.]]

[[file:formation-fluid-pressure-and-its-application_fig5-15.png|300px|thumb|{{figure number|3}}Example of how pressure is extrapolated from ISIP and FSIP on a Horner plot (pressure vs. psuedo or Horner time, or (T + ΔT)/ΔT. Copyright: Dahlberg;<ref name=ch05r5 /> courtesy Springer-Verlag.]]

DST pressures may not be reliable because the tool is not shut in long enough for pressure to stabilize at final reservoir pressure. A graphical procedure devised by Horner<ref name=ch05r10>Horner, D., R., 1951, Pressure build-up in wells: Proceedings of the Third World Petroleum Congress, The Hague, Section II, p. 503–521.</ref> infers the true reservoir pressure by extrapolating the shut-in periods to infinity.

DST pressures may not be reliable because the tool is not shut in long enough for pressure to stabilize at final reservoir pressure. A graphical procedure devised by Horner<ref name=ch05r10>Horner, D., R., 1951, Pressure build-up in wells: Proceedings of the Third World Petroleum Congress, The Hague, Section II, p. 503–521.</ref> infers the true reservoir pressure by extrapolating the shut-in periods to infinity.