Method for permeable zone detection
AssigneeSchlumberger Technology Corporation
InventorsPeter T. Wu, Alain Dumont, Pierre Campanac, David Linton Johnson
Life of this patent
Estimating the term…
Abstract
A method for estimating formation permeability from measured sonic wave Stoneley attributes and particularly the Stoneley attributes of slowness (DTst) and attenuation (ATTst), taking into consideration the existence of a heavy walled drill collar at the end of the drill string and the relative lack of borehole mud cake during a drilling operation. In the subject LWD application a real-time qualitative indication for fracture and permeable zones is estimated from Stoneley measurements. This information is useful to a driller to make important timely decisions about drilling and completion programs.
Claims13
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, said method comprising:
- determining process parameters including a desired frequency band to increase signal-to-noise ratio, wherein the frequency band depends on formation type and drilling noise;
- determining model input parameters for a waveform model including properties of rock formation and the borehole, including a borehole fluid and the drill collar;
- modeling a Stoneley waveform based on the input parameters including the drill collar radius, the drill collar material density, the drill collar material shear velocity and the drill collar material compressional velocity, and a range of discrete values for permeability;
- processing the modeled waveforms corresponding to the selected input values of permeability to obtain Stoneley wave slowness or Stoneley wave attenuation;
- generating a model curve of the Stoneley wave slowness or Stoneley wave attenuation as a function of permeability by using the values of permeability;
- transmitting a sonic wave and receiving a sonic Stoneley wave with a LWD tool including the drill collar;
- processing the received waveform for Stoneley wave slowness or Stoneley wave attenuation 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 wave slowness or Stoneley wave attenuation, estimating formation permeability from the attribute of the Stoneley wave measured during LWD operations.
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, said method comprising:
- determining process parameters including a desired frequency band to increase signal-to-noise ratio, wherein the frequency band depends on formation type and drilling noise;
- determining model input parameters for a waveform model including properties of rock formation and the borehole, including a borehole fluid and the drill collar;
- modeling a Stoneley waveform based on the input parameters including the drill collar radius, the drill collar material density, the drill collar material shear velocity and the drill collar material compressional velocity, 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;
- generating a model curve of slowness and attenuation attributes of Stoneley waveforms as a function of permeability by using the values 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.
Dependencies are inferred from the claim text.