Changes

[[file:applying-gravity-in-petroleum-exploration_fig15-11.png|300px|thumb|{{figure number|2}}Depth of investigation is tunable by means of varying the separation between two gravity measurements, Δ''z''. After McCulloh et al.<ref name=ch15r9>McCulloh, T. H., J. R. Kandle, J. E. Schoellhamer, 1968, Application of gravity measurements in wells to problems of reservoir evaluation: Transactions of the 9th Annual SPWLA Logging Symposium. Fundamental work describing the distance of sources seen by the borehole gravity meter.</ref> Copyright: SPWLA.]]

[[file:applying-gravity-in-petroleum-exploration_fig15-11.png|300px|thumb|{{figure number|2}}Depth of investigation is tunable by means of varying the separation between two gravity measurements, Δ''z''. After McCulloh et al.<ref name=ch15r9>McCulloh, T. H., J. R. Kandle, J. E. Schoellhamer, 1968, Application of gravity measurements in wells to problems of reservoir evaluation: Transactions of the 9th Annual SPWLA Logging Symposium. Fundamental work describing the distance of sources seen by the borehole gravity meter.</ref> Copyright: SPWLA.]]

[[:file:applying-gravity-in-petroleum-exploration_fig15-11.png|Figure 2]] shows how the depth of investigation is tunable by means of varying the separation between two gravity measurements, Δ''z''. The rule of thumb is that 90% of the gravity effect can be imaged at a distance away from the borehole within five times Δ''z''.

[[:file:applying-gravity-in-petroleum-exploration_fig15-11.png|Figure 2]] shows how the depth of investigation is tunable by means of varying the separation between two [[gravity]] measurements, Δ''z''. The rule of thumb is that 90% of the gravity effect can be imaged at a distance away from the borehole within five times Δ''z''.

==Depth of investigation of various logging methods==

==Depth of investigation of various logging methods==

==Logging procedure==

==Logging procedure==

In a typical logging operation, several downhole station locations are planned ahead of time. The tool is fitted to a conventional wireline and lowered to each station. Once the tool is stopped (in some wells it must be clamped to the side of the well), the measurement begins. The gravity values are telemetered to an operator at the surface. Because of vibrations, seismic activity, or residual tool movement, the measurements may take some time to settle to an acceptable noise level.

In a typical logging operation, several downhole station locations are planned ahead of time. The tool is fitted to a conventional wireline and lowered to each station. Once the tool is stopped (in some wells it must be clamped to the side of the well), the measurement begins. The [[gravity]] values are telemetered to an operator at the surface. Because of vibrations, seismic activity, or residual tool movement, the measurements may take some time to settle to an acceptable noise level.

==Tool limitations==

==Tool limitations==