Apparatus and methods of identifying rock properties in real-time during drilling, are provided. An apparatus includes an acoustic sensor installed in a drilling fluid circulation system of a drilling rig, the acoustic sensor coupled to one of the following: (i) a bell nipple, (ii) a gooseneck, or (iii) a standpipe. Raw acoustic sensor data generated real-time as a result of rotational contact of the drill bit with rock during drilling is received, and a plurality of acoustic characteristics are derived from the raw acoustic sensor data. The lithology type of rock undergoing drilling may be determined from the acoustic characteristics. Petrophysical properties of the rock undergoing drilling may be determined using a petrophysical properties evaluation algorithm employable to predict the petrophysical properties of rock undergoing drilling from the raw acoustic sensor data.

Determining a type of annular material in a wellbore comprises measuring an acoustic noise of one or more reference materials and thereby generating a corresponding one or more acoustic profiles, monitoring the annular material with an acoustic sensor positioned in the wellbore and thereby obtaining an acoustic response of the annular material, comparing the acoustic response with the one or more acoustic profiles using a processor communicably coupled to the acoustic sensor, and characterizing the annular material based on the comparison of the acoustic response and the one or more acoustic profiles.

In one embodiment, a method includes drilling a wellbore in a formation with a drilling tool. The method further includes receiving electromagnetic radiation using an opto-analytical device coupled to the drilling tool. The method also includes detecting vibrations associated with drilling the wellbore based on the received electromagnetic radiation.

Various embodiments include apparatus and methods to estimate properties of rock, drill bit, or a combination thereof associated with a drilling operation. The properties can include, but are not limited to, rock chip size, drill bit dullness, drilling efficiency, or a combination selected from rock chip size, drill bit dullness, and drilling efficiency. The estimate may be accomplished from correlating detected acoustic emission with detected electromagnetic emissions. In various embodiments, formation brittleness may be determined. The various estimates may be used to direct a drilling operation. Additional apparatus, systems, and methods are disclosed.

Systems and techniques may be used to obtaining information corresponding to a drill bit in use during downhole drilling in a first well. An example technique may include sending a laser pulse down a fiber optic cable in a second well, capturing, using distributed acoustic sensing (DAS), backscatter light propagated back from the laser pulse, and determining strain changes over the fiber optic cable based on a change in optical phase over a time period. The strain changes may be used to generate seismic while drilling (SWD) data. The example technique may include outputting drill bit data for the drill bit based on comparing the SWD data to a pilot signal.

A method includes drilling a wellbore into a subsurface using a drill bit and, for each of a plurality of depths of the drill bit in the wellbore, detecting, at each of a plurality of receiver stations located along a fiber optic cable disposed behind a casing string within the wellbore, a seismic signal created by the drill bit drilling the wellbore, sending an optical signal generated by the detection of the seismic signal from each of the plurality of receiver stations to an interrogator, sorting, using a computer processor, the optical signals by receiver station, and determining, using the computer processor, a seismic velocity using first breaks picked from the sorted optical signals.

The present disclosure involves a novel way of using drilling vibrations generated by the deformation of a rock formation in response to forces acting on the rock formation, where the forces are related to a drill bit and/or drilling fluid system, to identify the nature and occurrence of fractures, fracture swarms and other mechanical discontinuities (boundaries) such as bedding planes and/or faults that offset or otherwise separate rock formations with different mechanical rock properties.

A method that includes obtaining a first acoustic signal and transforming the first acoustic signal into a first frequency spectrum using a frequency transformer, where the first frequency spectrum comprises a first plurality of frequency data points. The method further includes partitioning the first plurality of frequency data points into a first plurality of energy bands using an energy band partitioning function. The method further includes determining a representative frequency for each of the first plurality of energy bands and determining a representative amplitude for each of the first plurality of energy bands, where the representative amplitude is determined based on an energy conservation principle. The method further includes determining a first energy band series, where the first energy band series comprises the representative amplitude and the representative frequency for each of the first plurality of energy bands and determining, using the first energy band series, an acoustic signal characteristic.

A method for acoustic logging a wellbore includes making sonic logging measurements while rotating a logging while drilling tool in a wellbore, the sonic logging measurements including low frequency measurements and high frequency measurements; estimating a low frequency slowness of the subterranean formation from the low frequency measurements; estimating a high frequency slowness of the subterranean formation from the high frequency measurements; and classifying the subterranean formation as homogeneous when a difference between the low frequency slowness and the high frequency slowness is less than a threshold and heterogeneous when the difference is greater than the threshold.

A computer implemented method that enables drill bit source focusing is described. The method includes obtaining, using at least one hardware processor, correlated drill bit gathers comprising a direct arrival from a downhole source to surface receivers; identifying, using the at least one hardware processor, at least one window around first breaks in the correlated drill bit gathers captured by the surface receivers, wherein the first breaks are isolated/bounded the at least one window; redatuming, using the at least one hardware processor, seismic data within the at least one window captured by respective surface receivers to generate source images; and generating, using the at least one hardware processor, a seismic migration image by multiplying the generated source images.