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1. (WO2009090465) METHOD FOR PERMEABLE ZONE DETECTION
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What is claimed is:
1. A method for estimating formation permeability using at least one attribute of

Stoneley waveforms in a borehole under logging while drilling conditions of a drill string with a drill collar at a distal end, and with a relative absence of mud cake along the borehole side walls, said method comprising the steps of:
determining process parameters including a desired frequency band;
determining model input parameters for a waveform model including properties of rock formation and the borehole, including the borehole fluid and a drill collar;
modeling a Stoneley waveform based on the input parameters and a range of
discrete values for permeability;
processing the modeled waveforms corresponding to the selected input values of permeability to obtain at least one Stoneley attribute;
interpolating between the values of permeability to generate a model curve of at least one Stoneley attribute as a function of permeability;
transmitting a sonic wave and receiving a sonic Stoneley wave with a logging
while drilling tool including a drill collar;
processing the received waveform for at least one Stoneley attribute using the
same processing method and processing parameters used to process the modeled waveforms; and
using the model curve that relates permeability to the Stoneley attribute,
estimating formation permeability from the attribute of the Stoneley wave
measured during LWD operations.
2. A method for estimating formation permeability using at least one attribute of Stoneley waveforms in a borehole under logging while drilling conditions as defined in claim 1 wherein said step of processing at least one attribute of modeled and measured Stoneley waveform comprises:
modeling and measuring a slowness attribute of Stoneley waveform.
3. A method for estimating formation permeability using at least one attribute of Stoneley waveforms in a borehole under logging while drilling conditions as defined in claim 1 wherein said step of processing at least one attribute of modeled and measured Stoneley waveform comprises:
modeling and measuring an attenuation attribute of Stoneley waveform.
4. A method for estimating formation permeability using at least one attribute of Stoneley waveforms in a borehole under logging while drilling conditions as defined in claim 1 wherein said step of processing at least one attribute of modeled and measured Stoneley waveform comprises:
modeling and measuring both the slowness attributes and attenuation attributes of
Stoneley waveforms.
5. A method for estimating formation permeability using slowness and attenuation attributes of Stoneley waveforms in a borehole under logging while drilling conditions as defined in claim 4 and further comprising the steps of :
computing a single estimate of permeability from the estimates, Ks and Ka obtained from the slowness and attenuation attributes of Stoneley waveforms in accordance
with the following formula for the weighted geometric mean Ks and Ka;
W84og(KJ*WsHog10{ig
K = W3 + W S
where: Wa, Ws > 0; Wa + W8 = 1.
6. A method for estimating formation permeability using slowness and attenuation attributes of Stoneley waveforms in a borehole under logging while drilling conditions as defined in claim 1 wherein said step of determining model input parameters for a borehole fluid include the steps of :
determining borehole fluid compressional velocity; and
determining borehole fluid density.
7. A method for estimating formation permeability using slowness and attenuation attributes of Stoneley waveforms in a borehole under logging while drilling conditions as defined in claim 1 wherein said step of determining model input parameters for a drill collar includes the steps of :
determining the drill collar radius;
determining at least one of the drill collar material compressional and shear
velocity; and
determining the drill collar material density.
8. A method for estimating formation permeability using slowness and attenuation attributes of Stoneley waveforms in a borehole under logging while drilling conditions as defined in claim 4 wherein said step of determining model input parameters comprises the step of :
determining values for;
borehole radius
borehole fluid compressional velocity
borehole fluid density collar radius
collar material compressional velocity
collar material shear velocity
collar material density
formation porosity
saturated formation compressional velocity
saturated formation shear velocity
average formation density
rock grain density
rock grain bulk modulus
pore fluid bulk modulus
pore fluid density, and
pore fluid viscosity.
9. A method for estimating formation permeability using at least one attribute of

Stoneley waveforms in a borehole under logging while drilling conditions as defined in claim 1 wherein said step of processing at least one attribute of modeled and measured Stoneley waveform comprises:
processing with a slowness-time-coherence algorithm using a frequency from
within a band of from 0.5 KHz to 10 KHz.
10. A method for estimating formation permeability using slowness and attenuation attributes of Stoneley waveforms in a borehole under logging while drilling conditions with a drill string having a drill collar at a distal end, and with a relative absence of mud cake along the borehole side walls, said method comprising the steps of:
determining process parameters including a desired frequency band;
determining model input parameters for a waveform model including properties of rock formation and the borehole, including the borehole fluid and a drill collar; modeling a Stoneley waveform based on the input parameters and a range of
discrete values for permeability;
processing the modeled waveforms corresponding to the selected input values of permeability to obtain slowness and attenuation attributes of Stoneley
waveforms;
interpolating between the values of permeability to generate a model curve of
slowness and attenuation attributes of Stoneley waveforms as a function of
permeability;

processing the measured waveform for slowness and attenuation attributes of
Stoneley waveforms using the same processing method used to process the
modeled waveforms;
applying the slowness and attenuation attributes of Stoneley waveforms to
corresponding modeled curves of the Stoneley attributes as a function of
permeability; and
using the curves that relate permeability to the Stoneley attributes, estimating
permeability from the attributes of the Stoneley wave measured during LWD
operations.
11. A method for estimating formation permeability using slowness and attenuation attributes of Stoneley waveforms in a borehole under logging while drilling conditions with a drill string having a drill collar at a distal end, and with a relative absence of mud cake along the borehole side walls as defined in claim 10 wherein said step of determining model input parameters comprises the steps of:
determining values for;
borehole radius
borehole fluid compressional velocity
borehole fluid density
collar radius
collar material compressional velocity
collar material shear velocity
collar material density
formation porosity
saturated formation compressional velocity
saturated formation shear velocity
average formation density
rock grain density
rock grain bulk modulus
pore fluid bulk modulus
pore fluid density, and
pore fluid viscosity.
12. A method for estimating formation permeability using slowness and attenuation attributes of Stoneley waveforms in a borehole under logging while drilling conditions with a drill string having a drill collar at a distal end, and with a relative absence of mud cake along the borehole side walls as defined in claim 11 and further comprising the steps of: computing a single estimate of permeability from the estimates, K5 and Ka
obtained from the slowness and attenuation attributes of Stoneley waveforms in accordance with the following formula for the weighted geometric mean Ks and Ka;

K = IO Wa + W.
where: Wa, Ws > 0; Wa + Ws = 1.
13. A method for estimating formation permeability using slowness and attenuation attributes of Stoneley waveforms in a borehole under logging while drilling conditions with a drill string having a drill collar at a distal end, and with a relative absence of mud cake along the borehole side walls as defined in claim 12 wherein said step of processing slowness and attenuation attributes of modeled and measured Stoneley waveforms comprises:
processing with a slowness-time-coherence algorithm using a frequency from
within a band of from 0.5 KHz to 10 KHz.