Methods for locating oil or gas deposits employing temperature and/or geothermal gradient measurements

Claim 3

The method of claim 1 including: determining a temperature (T a ') at a second known depth beneath said location, wherein said second depth is below said first depth; determining a temperature (T r ') representative of the average temperature for the second depth within a geographical area within which the location is situated; and determining a temperature difference (ΔT') according to the relationship ΔT'=T a '-T r ', wherein for ΔT and ΔT' both of negative value and ΔT' of greater magnitude than ΔT, it is likely than an oil or gas deposit is present below said second depth, wherein for ΔT and ΔT' both of negative value and ΔT' of lesser magnitude than ΔT, it is likely that a first oil or gas deposit is present between said first and second depths and likely that a second oil or gas deposit is present below said second depth, and wherein for ΔT of negative value and ΔT' of zero or positive value, predicting that an oil or gas deposit is present between said first and second depths, and that no oil or gas deposit is below said second depth.

Claim 4

The method of claim 2 wherein the method is repeated for a plurality of sets of first and second known depths at the same location.

Claim 5

The method of claim 3 wherein the second known depth of one set of first and second known depths is the first known depth of the next succeeding set of first and second known depths.

Claim 6

The method of claim 4 wherein the temperature T a for each known depth is determined during the course of drilling a borehole at said location.

Claim 7

The method of claim 1 wherein said first depth is the bottom hole depth of a borehole previously drilled at the location, and the temperature T a is the bottom hole temperature of said borehole.

Claim 8

The method of claim 2 wherein said second depth is the bottomhole depth of a borehole previously drilled at the location and wherein the temperature T a ' is the bottomhole temperature of said borehole, and wherein said first depth is an intermediate depth in said borehole and said temperature T a is the temperature at said intermediate depth in said borehole.

Claim 9

The method of claim 4 wherein for the lowest set of first and second depths the second depth is the bottom hole depth of a previously drilled borehole and all other known depths are intermediate depths in the borehole and all temperatures T a are borehole temperatures.

Claim 10

The method of claim 1 wherein the geographical area contains a plurality of locations, and wherein the temperature T r for any known depth is the average of the temperatures T a for said known depth from the plurality of locations.

Claim 11

The method of claim 9 wherein said method is applied to each location in turn.

Claim 12

The method of claim 1 wherein the known depth is about the surface of the earth.

Claim 13

The method of claim 1 wherein the known depth is the surface, wherein the temperature (T a ) is the mean annual atmospheric temperature for the location and wherein the temperature (T r ) is the mean annual atmospheric temperature for the geographical area.

Claim 14

The method of claim 1 wherein the known depth is at the ocean bottom, wherein the temperature (T a ) is the benthic temperature near the ocean bottom at said location, and wherein (T r ) is the average benthic temperature at the ocean bottom at the known depth within the geographical area.

Claim 17

The method of claim 14, further comprising: determining a geothermal gradient (G a ') at said location across a second interval from the surface to a second known depth, wherein said second depth is below said first depth; and determining a geothermal gradient difference (ΔG') according to the relationship ΔG'=G a '-G r , wherein for ΔG and ΔG' both of negative value and wherein the magnitude of ΔG' is greater than the magnitude of ΔG, it is likely that an oil or gas deposit is present below said second known depth, wherein for ΔG and ΔG' both of negative value and wherein ΔG is of greater magnitude than ΔG', it is likely that a first oil or gas deposit is present between said first and second known depths, and it is likely that a second oil or gas deposit is present below said second known depth, wherein for ΔG of positive value and ΔG' of negative value it is likely that a first oil or gas deposit is present above said first known depth and a second oil or gas deposit is present below said second known depth, wherein for ΔG of negative value and ΔG' of positive value it is likely an oil or gas deposit is present between said first and second known depth and likely that no oil or gas deposit is present below said second known depth.

Claim 18

The method of claim 15 applied to a plurality of intervals from the surface to a plurality of known depths.

Claim 21

The method of claim 17, further comprising: determining a third geothermal gradient (G 3 ) across a third depth interval below said second interval; and comparing the values of G 1 , G 2 and G 3 , wherein for G 1 greater than G 2 greater than G 3 , it is likely an oil or gas deposit is present below said third depth interval, wherein for G 1 less than G 2 and G 2 greater than G 3 , it is likely an oil or gas deposit is present within said second interval, wherein for G 1 greater than G 2 and G 2 less than G 3 it is likely an oil or gas deposit is present in said third interval, and wherein for G 1 less than G 2 and G 2 less than G 3 it is likely that an oil or gas deposit is not present below said third interval.

Claim 22

The method of claim 18 wherein the geothermal gradients are obtained in the process of drilling a borehole.

Claim 23

The method of claim 18 wherein a geothermal gradient is obtained for a plurality of intervals within a borehole, wherein the geothermal gradient G 3 becomes the geothermal gradient G 1 of succeeding predictions.