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US 7,660,196 B2Granted
Methods for processing dispersive acoustic waveforms
AssigneeSchlumberger Technology Corporation
InventorsYoshiyuki Saiki, Oliver Skelton, Jahir Pabon, Bikash K. Sinha
Life of this patent
Estimating the term…
Abstract
A method for processing acoustic data comprising applying a dynamic filter band. The method and apparatus may be particularly adapted to processing sonic data to measure formation slowness in a borehole.
Claims16
A method of processing flexural wave acoustic data from a tool in a borehole traversing a formation, comprising:
- using the tool to transmit and receive the flexural wave acoustic data in the borehole;
- generating a set of estimated slowness curves from the flexural wave acoustic data;
- determining an upper limit for a frequency filter band;
- determining a lower frequency limit for the frequency filter band;
- compensating for effect of a tool comprising defining a modified borehole diameter by determining the residual difference R between two dispersion curves as
- R
- =
- ∑
- f
-
-
- S
- S
- k
-
- (
- S
- ,
- f
- )
-
- {
- S
- tool
-
- (
- S
- ,
- f
- ,
- d
- )
- -
- S
- empty
-
- (
- S
- ,
- f
- ,
- d
- +
- a
-
- (
- S
- ,
- d
- )
- )
- }
-
- 2
- wherein S is formation shear slowness;
- Sss is sensitivity to the formation shear slowness, Stool is a dispersion curve with a tool present;
- Sempty is a dispersion curve without the presence of a tool, d is borehole diameter;
- f is frequency;
- and a is a constant.
56 more elements
A method of processing flexural wave acoustic data from a tool in a borehole traversing a formation, comprising:
- using the tool to transmit and receive the flexural wave acoustic data in the borehole;
- generating a set of estimated slowness curves from the flexural wave acoustic data;
- determining an upper limit for a frequency filter band;
- determining a lower frequency limit for the frequency filter band;
- determining effect of a tool;
- and
- applying the frequency filter band and the tool effect in calculating semblance, wherein an uncertainty e in a shear slowness is estimated as:
- e
-
- (
- S
- ,
- f
- )
- =
- s
- hd
-
- (
- S
- ,
- f
- )
- s
- shear
-
- (
- S
- ,
- f
- )
-
- δ
- hd
- ,
- wherein S is formation shear slowness;
- f is frequency, sshear is sensitivity to the formation shear slowness, shd is sensitivity to borehole diameter;
- and δhd is uncertainty in borehole diameter measurement.
35 more elements
A method of processing acoustic data collected using a borehole tool disposed in a borehole comprising:
- defining a modified borehole diameter, said modified borehole diameter including the effects of the presence of said borehole tool in said borehole;
- using the borehole tool to transmit and receive the acoustic data in the borehole;
- processing said acoustic data at least in part using the modified borehole diameter such that the processed acoustic data includes the effects of the presence of said borehole tool in said borehole,
- wherein defining the modified borehole diameter comprises minimizing difference between flexural dispersion in the presence of said borehole tool and flexural dispersion in the absence of said borehole tool over a selected bandwidth,
- wherein minimizing difference between flexural dispersion in the presence of said borehole tool and flexural dispersion in the absence of said borehole tool. over a selected bandwidth comprises calculating the residual difference R between two dispersion curves as
- R
- =
- ∑
- f
-
-
- S
- S
- s
-
- (
- S
- ,
- f
- )
-
- {
- S
- tool
-
- (
- S
- ,
- f
- ,
- d
- )
- -
- S
- empty
-
- (
- S
- ,
- f
- ,
- d
- +
- a
-
- (
- S
- ,
- d
- )
- )
- }
-
- 2
- wherein S is formation shear slowness;
- SSs is sensitivity to the formation shear slowness, Stool is a dispersion curve with a tool present;
- Sempty is a dispersion curve without the presence of a tool, d is borehole diameter;
- is frequency;
- and a is a constant.
56 more elements
Dependencies are inferred from the claim text.