Changes

==How the tool measures gravity==

==How the tool measures gravity==

[[file:applying-gravity-in-petroleum-exploration_fig15-10.png|300px|thumb|{{figure number|1}}Fundamentals of measuring density using a borehole gravity sensor. From Schowalter;<ref name=Schowalter1979>Schowalter, T.T., 1979, Mechanics of secondary hydrocarbon migration and entrapment: AAPG Bulletin, vol. 63, no. 5, p. 723–760.</ref> courtesy AAPG.]]

[[file:applying-gravity-in-petroleum-exploration_fig15-10.png|300px|thumb|{{figure number|1}}Fundamentals of measuring density using a borehole gravity sensor. From Schowalter;<ref name=Schowalter1979>Schowalter, T. T., 1979, [http://archives.datapages.com/data/bulletns/1977-79/data/pg/0063/0005/0700/0723.htm Mechanics of secondary hydrocarbon migration and entrapment]: AAPG Bulletin, vol. 63, no. 5, p. 723–760.</ref> courtesy AAPG.]]

[[:file:applying-gravity-in-petroleum-exploration_fig15-10.png|Figure 1]] illustrates the fundamentals of measuring density using a [[borehole gravity]] sensor. Two gravity measurements, ''g''₁ and ''g''₂, are made downhole, separated in depth by Δ''z''. The value ''G'' is the universal gravity constant. Thus, the gravity gradient, Δ''g''/Δ''z'', is related directly to the density of the intervening layer. The result is a direct computation of the bulk density of that layer.

[[:file:applying-gravity-in-petroleum-exploration_fig15-10.png|Figure 1]] illustrates the fundamentals of measuring density using a [[borehole gravity]] sensor. Two gravity measurements, ''g''₁ and ''g''₂, are made downhole, separated in depth by Δ''z''. The value ''G'' is the universal gravity constant. Thus, the gravity gradient, Δ''g''/Δ''z'', is related directly to the density of the intervening layer. The result is a direct computation of the bulk density of that layer.