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US 4,786,796 AGranted
Method for determining formation characteristics with enhanced vertical resolution
AssigneeSchlumberger Technology Corporation
InventorsCharles Flaum, James E. Galford, Steven V. Ducket
Life of this patent
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Abstract
A method for determining a characteristic of a subsurface geological formation enhances the vertical resolution of dual-detector measurements by utilizing a continuous calibration factor which is obtained from an environmentally compensated characteristic derived from at least two resolution-matched sensor signals, and from a resolution-matched sensor signal from the near-detector of the tool.
Claims24
A method for determining the density of a subsurface geological formation traversed by a borehole, comprising the steps of:
- (a) passing a logging tool through the borehole, the logging tool having associated therewith a signal source and at least two signal sensors spaced from the signal source by different distances;
- (b) transmitting a signal from the signal source into the subsurface geological formation;
- (c) generating sensor signals from the at least two signal sensors, in response to the signal from the signal source received by the at least two signal sensors;
- (d) matching the vertical resolution of the generated sensor signals from the at least two signal sensors;
- (e) determining an environmentally compensated density from the at least two resolution matched sensor signals;
- (f) determining the density from the unmatched sensor signal from the signal sensor spaced the least distance from the signal source;
- (g) determining the density from the resolution matched sensor signal from the signal sensor spaced the least distance from the signal source;
- (h) determining the difference between the density of step (e) and the density of step (g);
- and
- (i) combining the result of step (h) with the density of step (f) to determine the density wherein the vertical resolution of the density is enhanced.
7 more elements
The method for determining the porosity index of a subsurface geological formation traversed by a borehole, comprising the steps of:
- (a) passing a logging tool through the borehole, the logging tool having associated therewith a signal source and at least two signal sensors spaced from the signal source by different distances;
- (b) transmitting a signal from the signal source into the subsurface geological formation;
- (c) generating sensor signals from the at least two signal sensors, in response to the signal from the signal source received by the at least two signal sensors;
- (d) matching the vertical resolution of the generated sensor signals from the at least two signal sensors;
- (e) determining an environmentally compensated porosity index from the at least two resolution matched sensor signals;
- (f) determining a continuous calibration factor utilizing the environmentally compensated porosity index of step (e) and the resolution matched sensor signal from the signal sensor spaced the least distance from the signal source;
- (g) calibrating the unmatched sensor signal from the signal sensor spaced the least distance from the signal source by applying the continuous calibration factor thereto;
- and
- (h) determining a porosity index from the calibrated, unmatched sensor signal of step (g), wherein the vertical resolution of the porosity index is enhanced.
6 more elements
A method for determining a characteristic of a subsurface geological formation traversed by a borehole, comprising the steps of:
- (a) passing a logging tool through the borehole, the logging tool having associated therewith a signal sourcre and at least two signal sensors spaced from the signal source by different distances;
- (b) transmitting a signal from the signal source into the subsurface geological formation;
- (c) generating sensor signals from the at least two signal sensors, in response to the signal from the signal source received by the at least two signal sensors;
- (d) matching the vertical resolution of the generated sensor signals from the at least two signal sensors;
- (e) determining an environmentally compensated characteristic of the subsurface geological formation from a combination of the resolution-matched sensor signals;
- (f) determining a continuous calibration factor by utilizing the environmentally compensated characteristic of step (e) and the resolution matched sensor signal from the signal sensor spaced the least distance from the signal source;
- (g) calibrating the unmatched sensor signal from the signal sensor spaced the least distance from the signal source with the continuous calibration factor;
- and
- (h) determining the desired characteristic from the calibrated unmatched signal sensor of step (g), wherein the vertical resolution of the desired characteristic is enhanced.
6 more elements
Dependencies are inferred from the claim text.