Changes

==Salt body geometry==

==Salt body geometry==

[[file:applying-gravity-in-petroleum-exploration_fig15-13.png|thumb|{{figure number|2}}(A) Predicted BHGM logs through a salt body in the Gulf of Mexico. (B) Model of the salt body. (C) Seismic section through the salt body. Copyright: ARCO Exploration and Production Technology, 1997.{{citation needed}}]]

[[file:applying-gravity-in-petroleum-exploration_fig15-13.png|thumb|{{figure number|2}}(A) Predicted BHGM logs through a salt body in the Gulf of Mexico. (B) Model of the salt body. (C) Seismic section through the salt body. Copyright: ARCO Exploration and Production Technology.]]

In many Gulf of Mexico prospects, salt plays a key role in acting as a structural trap. Overhanging salt often forms seals, and sediments on salt flanks can have structural and stratigraphic pinch-outs against the salt. The exact shape of the salt is critical in understanding these traps. Unfortunately, seismic imaging often tends to be poor in these prospects. In [[:file:applying-gravity-in-petroleum-exploration_fig15-13.png|Figure 2's]] synthetic model (taken from a real structure), if a [[borehole gravity]] log were run, it would be able to tell conclusively which of the two [[seismic interpretation]]s shown below in the figure was valid. Either interpretation would have a significant impact on the completion and economics of the exploration play.  [[:file:applying-gravity-in-petroleum-exploration_fig15-13.png|Figure 2(A)]] is predicted BHGM logs through a salt body in the Gulf of Mexico, [[:file:applying-gravity-in-petroleum-exploration_fig15-13.png|2(B)]] is a model of the salt body, and  [[:file:applying-gravity-in-petroleum-exploration_fig15-13.png|2(C)]] is a seismic section through the salt body shown in the model (B).

In many Gulf of Mexico prospects, salt plays a key role in acting as a structural trap. Overhanging salt often forms seals, and sediments on salt flanks can have structural and stratigraphic pinch-outs against the salt. The exact shape of the salt is critical in understanding these traps. Unfortunately, seismic imaging often tends to be poor in these prospects. In [[:file:applying-gravity-in-petroleum-exploration_fig15-13.png|Figure 2's]] synthetic model (taken from a real structure), if a [[borehole gravity]] log were run, it would be able to tell conclusively which of the two [[seismic interpretation]]s shown below in the figure was valid. Either interpretation would have a significant impact on the completion and economics of the exploration play.  [[:file:applying-gravity-in-petroleum-exploration_fig15-13.png|Figure 2(A)]] is predicted BHGM logs through a salt body in the Gulf of Mexico, [[:file:applying-gravity-in-petroleum-exploration_fig15-13.png|2(B)]] is a model of the salt body, and  [[:file:applying-gravity-in-petroleum-exploration_fig15-13.png|2(C)]] is a seismic section through the salt body shown in the model (B).

==Monitoring well drawdown==

==Monitoring well drawdown==

[[file:applying-gravity-in-petroleum-exploration_fig15-14.png|left|thumb|{{figure number|3}}Synthetic model of the configuration of a theoretical drawdown gas cone around a producing well, modeled after the Prudhoe Bay field, Alaska. Copyright: ARCO Exploration and Production Technology, 1997.]]

[[file:applying-gravity-in-petroleum-exploration_fig15-14.png|left|thumb|{{figure number|3}}Synthetic model of the configuration of a theoretical drawdown gas cone around a producing well, modeled after the Prudhoe Bay field, Alaska. Copyright: ARCO Exploration and Production Technology.]]

One of the most attractive aspects of borehole gravity applications is its ability to detect gas, oil, and water contacts at large distances from the borehole. It can do this through multiple casing strings and formation damage—conditions where the neutron density tool performs poorly. In many hydrocarbon reservoirs, the oil has a gas cap. Frequently, these reservoirs have an underlying water zone. The shape of these interfaces over time is critical to production strategy. Methods can determine where those contacts exist in the well-bore, but only borehole gravity can determine their shape away from the well. Because the interfaces are mobile with time, their movement can be monitored with borehole gravity.

One of the most attractive aspects of borehole gravity applications is its ability to detect gas, oil, and water contacts at large distances from the borehole. It can do this through multiple casing strings and formation damage—conditions where the neutron density tool performs poorly. In many hydrocarbon reservoirs, the oil has a gas cap. Frequently, these reservoirs have an underlying water zone. The shape of these interfaces over time is critical to production strategy. Methods can determine where those contacts exist in the well-bore, but only borehole gravity can determine their shape away from the well. Because the interfaces are mobile with time, their movement can be monitored with borehole gravity.