Changes

==RFT tool==

==RFT tool==

[[file:formation-fluid-pressure-and-its-application_fig5-16.png|thumb|{{figure number|1}}Fom .<ref name=ch05r5>Dahlberg, E., C., 1994, Applied Hydrodynamics in Petroleum Exploration, 2nd ed.: New York, Springer-Verlag, 295 p. Excellent subsurface fluid pressure reference. Covers hydrodynamic and static fluids.</ref> Copyright: Springer-Verlag.]]

[[file:formation-fluid-pressure-and-its-application_fig5-16.png|thumb|{{figure number|1}}From <ref name=ch05r5>Dahlberg, E., C., 1994, Applied Hydrodynamics in Petroleum Exploration, 2nd ed.: New York, Springer-Verlag, 295 p.</ref> Copyright: Springer-Verlag.]]

The repeat formation tester (RFT) tool was designed to measure formation pressure quickly and accurately. It measures pressure at specific points on the borehole wall. The diagram below shows a typical RFT tool. Formation pressure is measured by the formation sampler (see diagram in [[:file:formation-fluid-pressure-and-its-application_fig5-16.png|Figure 1]]) when it is extended from the tool to contact the formation. Fluid samples from the formation can also be taken with the tool.

The repeat formation tester (RFT) tool was designed to measure formation pressure quickly and accurately. It measures pressure at specific points on the borehole wall. The diagram below shows a typical RFT tool. Formation pressure is measured by the formation sampler (see diagram in [[:file:formation-fluid-pressure-and-its-application_fig5-16.png|Figure 1]]) when it is extended from the tool to contact the formation. Fluid samples from the formation can also be taken with the tool.

==Example: comparing RFT to DST==

==Example: comparing RFT to DST==

[[file:formation-fluid-pressure-and-its-application_fig5-17.png|thumb|{{figure number|2}}. Copyright: Gunter and Moore, 1987; courtesy JPT.]]

[[file:formation-fluid-pressure-and-its-application_fig5-17.png|thumb|{{figure number|2}}From<ref name=ch05r9 />. Courtesy JPT.]]

[[:file:formation-fluid-pressure-and-its-application_fig5-17.png|Figure 2]] is a plot of reservoir pressure vs. depth from a low-[[permeability]] chalk reservoir. The RFT data clearly show the hydrostatic gradient, the gas gradient, and the gas-water contact. Making the same interpretation from the DST data in this example is very difficult because data are from a low-permeability chalk reservoir. Reliable pressures are difficult to obtain in low-permeability reservoirs with DSTs. Extrapolated DST shut-in pressures from a partial buildup may not reflect actual fluid pressures. As rock quality increases, extrapolated pore pressure from DST buildup falls more and more closely to actual fluid pressure.

[[:file:formation-fluid-pressure-and-its-application_fig5-17.png|Figure 2]] is a plot of reservoir pressure vs. depth from a low-[[permeability]] chalk reservoir. The RFT data clearly show the hydrostatic gradient, the gas gradient, and the gas-water contact. Making the same interpretation from the DST data in this example is very difficult because data are from a low-permeability chalk reservoir. Reliable pressures are difficult to obtain in low-permeability reservoirs with DSTs. Extrapolated DST shut-in pressures from a partial buildup may not reflect actual fluid pressures. As rock quality increases, extrapolated pore pressure from DST buildup falls more and more closely to actual fluid pressure.

==Operating an RFT survey==

==Operating an RFT survey==

The table below explains how to operate an RFT survey (see .<ref name=ch05r9>Gunter, J., M., Moore, C., V., 1987, Improved use of wireline testers for reservoir evaluation: Journal of Petroleum Technology, p. 635–644. Good explanation of the use and interpretation of wireline pressure testers.</ref>

The table below explains how to operate an RFT survey (see<ref name=ch05r9>Gunter, J., M., Moore, C., V., 1987, Improved use of wireline testers for reservoir evaluation: Journal of Petroleum Technology, p. 635–644.</ref>).

{| class = "wikitable"

{| class = "wikitable"

==Controlling RFT quality==

==Controlling RFT quality==

The table below describes how to control RFT quality. For details, see .<ref name=ch05r9 />

The table below describes how to control RFT quality. For details, see<ref name=ch05r9 />.

{| class = "wikitable"

{| class = "wikitable"