An example apparatus includes a drill bit body and a leg extending from the drill bit body. A journal may extend from the leg, with a gamma ray detector at least partially within the journal. In certain embodiments, the gamma ray detector may be confined within a pressure protective cavity at least partially within the arm of the journal. In certain embodiments, the gamma ray detector may be a scintillator aligned with at least one of a photomultiplier, photodiodes, or phototransistors.

Disclosed are tools, systems, and methods for detecting one or more underground acoustic sources and localizing them in depth and radial distance from a wellbore, for example, for the purpose of finding underground fluid flows, such as may result from leaks in the well barriers. In various embodiments, acoustic-source detection and localization are accomplished with an array of at least three acoustic sensors disposed in the wellbore, in conjunction with array signal processing.

Disclosed are tools, systems, and methods for detecting one or more underground acoustic sources and localizing them in depth and radial distance from a wellbore, for example, for the purpose of finding underground fluid flows, such as may result from leaks in the well barriers. In various embodiments, acoustic-source detection and localization are accomplished with an array of at least three acoustic sensors disposed in the wellbore, in conjunction with array signal processing.

A sensor system for use in a wellbore is provided that can include a piezoelectric transducer for transmitting an acoustic wave into a fluid medium positioned in the wellbore by repeatedly bending between two positions in response to an actuation signal. The piezoelectric transducer can include at least four piezoelectric layers stacked on top of one another. Each of the four piezoelectric layers can be coupled to an adjacent layer via a bonding material. Each of the four piezoelectric layers can include a piezoelectric material, a top electrode coupled to a top surface of the piezoelectric material, and a bottom electrode coupled to a bottom surface of the piezoelectric material. The sensor system can also include a hydrophone for detecting a reflection or a refraction of the acoustic wave off an object in the wellbore and transmitting an associated signal to a processing device.

An apparatus for acquiring seismic wave data includes a network of geophones and a seismic wave data receiving device coupled to the network and configured to receive the seismic wave data as an optical signal and process the seismic data in real time to provide locations and corresponding sizes of fractures in an earth formation. The network of geophones includes: a plurality of geophone channels, each channel having an array of geophones coupled to a field digitizer unit; an array of geophone patches having geophone channels connected in series by a metallic conductor; a plurality of geophone branches having a metallic conductor and a branch digitizer unit to connect geophone patches in series; a plurality of electrical to optical signal converters for converting signals received from branch digitizer units for transmission using an optical fiber; and a plurality of optical fiber segments for transmitting optical signals to the receiving device.

An apparatus for acquiring seismic wave data includes a network of geophones and a seismic wave data receiving device coupled to the network and configured to receive the seismic wave data as an optical signal and process the seismic data in real time to provide locations and corresponding sizes of fractures in an earth formation. The network of geophones includes: a plurality of geophone channels, each channel having an array of geophones coupled to a field digitizer unit; an array of geophone patches having geophone channels connected in series by a metallic conductor; a plurality of geophone branches having a metallic conductor and a branch digitizer unit to connect geophone patches in series; a plurality of electrical to optical signal converters for converting signals received from branch digitizer units for transmission using an optical fiber; and a plurality of optical fiber segments for transmitting optical signals to the receiving device.

An apparatus and method for estimating at least one parameter of interest of an earth formation including an estimation of the parameter of interest using a time-dependent ratio of information obtained from at least one neutron detector through the exposure of the earth formation to a radiation source, particularly a pulsed nuclear source. The apparatus includes a processor and storage subsystem with a program that, when executed, implements the method. Also, an apparatus and method for estimating at least one parameter of interest of an earth formation including an estimation of the parameter of interest using a first component and a second component of an information set obtained using a single radiation detector.

A method of distributed acoustic sensing includes providing a fiber optic distributed acoustic sensing system having a cable. A straight optical fiber extends parallel to a longitudinal axis of the cable along the cable length. A helically wrapped optical fiber extends along the cable length. The method includes transmitting optical signals into and receiving backscattered signals out of the optical fibers consisting of a component of said optical signals which component has been backscattered from impurities or inhomogeneities in the optical fibers, observing changes in the backscattered signals caused by axial stretching and compressing of the optical fibers caused by an incident wave, comparing the backscattered signals of the straight optical fiber and the helically wrapped fiber, and determining, based on the comparing of the backscattered signals, a direction of wave propagation of the incident wave with respect to the fiber axis for detecting broadside waves and axial waves distinguishably.

A method of distributed acoustic sensing includes providing a fiber optic distributed acoustic sensing system having a cable. A straight optical fiber extends parallel to a longitudinal axis of the cable along the cable length. A helically wrapped optical fiber extends along the cable length. The method includes transmitting optical signals into and receiving backscattered signals out of the optical fibers consisting of a component of said optical signals which component has been backscattered from impurities or inhomogeneities in the optical fibers, observing changes in the backscattered signals caused by axial stretching and compressing of the optical fibers caused by an incident wave, comparing the backscattered signals of the straight optical fiber and the helically wrapped fiber, and determining, based on the comparing of the backscattered signals, a direction of wave propagation of the incident wave with respect to the fiber axis for detecting broadside waves and axial waves distinguishably.

A method for estimating uncertainties in determining hypocenters of seismic events occurring in subsurface formations according to one aspect includes determining estimates of event locations by choosing local peaks in summed amplitude of seismic energy detected by an array of sensors disposed above an area of the subsurface to be evaluated. For each peak, the following is performed: recomputing the summed amplitude response for a selected set of points of comprising small perturbations in time and space from the estimated event locations; computing second derivatives of log likelihood function from the stacked responses at the estimated location and the perturbed locations; assembling the second derivatives into a Fisher information matrix; computing an inverse of the Fisher information matrix; determining variances of estimated parameters from the elements from the diagonal of the inverted matrix; and computing standard deviations of the estimated parameters by calculating a square root of the variances.