A well log is scanned for one or more dimensions that describe one or more features of a well. Each dimension includes a plurality of values in a numerical format that represents each dimension. A missing value is detected in a first plurality of values of a first dimension of the well log. The first dimension of the well log is transformed, in response to the missing value, into a first image that visually depicts the first dimension including the first plurality of values and the missing value. Based on the first image and based on an image analysis algorithm a second image is created that visually depicts the first plurality of values and includes a found depiction visually depicting a found value in place of the missing value. The found depiction is converted, based on the second image, into a first value in the numerical format.

Systems and methods are provided for obtaining a flexural-attenuation measurement for cement evaluation that may be effective even for wells with relatively thick casings. A method includes emitting an acoustic signal at a casing in a well that excites the casing into generating an acoustic response signal containing acoustic waves, such as Lamb waves. The Lamb waves include flexural waves and extensional waves. The casing may be relatively large, having a thickness of at least 16 mm. The acoustic response signal may be detected and filtered to reduce a relative contribution of the extensional waves. This may correspondingly increase a relative contribution of the flexural waves. The filtered acoustic response signal may be used as a flexural-attenuation measurement for cement evaluation.

Systems and methods are provided for obtaining a flexural-attenuation measurement for cement evaluation that may be effective even for wells with relatively thick casings. A method includes emitting an acoustic signal at a casing in a well that excites the casing into generating an acoustic response signal containing acoustic waves, such as Lamb waves. The Lamb waves include flexural waves and extensional waves. The casing may be relatively large, having a thickness of at least 16 mm. The acoustic response signal may be detected and filtered to reduce a relative contribution of the extensional waves. This may correspondingly increase a relative contribution of the flexural waves. The filtered acoustic response signal may be used as a flexural-attenuation measurement for cement evaluation.

A method, including: obtaining Earth models including velocity, anisotropy, and attenuation reconstructing a source wavefield using the Earth models; reconstructing a receiver wavefield using the Earth models, wherein the reconstructing the source wavefield and the receiver wavefield each include applying an attenuation operator that increases an amplitude of down-going wavefields within an attenuation body and that decreases an amplitude of up-going wavefields within the attenuation body; applying an imaging condition to the source wavefield and receiver wavefield for a plurality of shots; and generating a subsurface image by stacking images for the plurality of shots.

A method, including: obtaining Earth models including velocity, anisotropy, and attenuation reconstructing a source wavefield using the Earth models; reconstructing a receiver wavefield using the Earth models, wherein the reconstructing the source wavefield and the receiver wavefield each include applying an attenuation operator that increases an amplitude of down-going wavefields within an attenuation body and that decreases an amplitude of up-going wavefields within the attenuation body; applying an imaging condition to the source wavefield and receiver wavefield for a plurality of shots; and generating a subsurface image by stacking images for the plurality of shots.

A method of obtaining an equivalent tool model includes obtaining a set of known well data, in which the known well data includes sensor data measured by a logging tool and an actual dispersion response, and the logging tool has an actual tool size. The method also includes obtaining one or more well parameters from the known well data, and inputting the one or more well parameters and a model tool size into a rigid tool model. The method further includes obtaining an estimated dispersion response from the rigid tool model, and fitting the estimated dispersion response to the actual dispersion response by adjusting the model tool size.

The disclosed device provides a high-accuracy plunger arrival detection system comprising a low-power magnetometer with high sensitivity and which is capable of sampling low or high intensity magnetic fields. The device processes gathered data from sensors, stores at least some processed data in memory, executes a trending algorithm which compares the magnetic field of the plunger to the ambient magnetic field or a predetermined set of initialization values, and generates an output which is relayed to a well controller. An output signal may be via hard wire, RF, wireless or other known means. In addition, the implementation of two sensing devices mounted in series and in spaced relation to each other, can provide for an actual plunger average velocity. An actual plunger average velocity, as opposed to approximate average velocity, can be used to better optimize well control and improve safety of the overall well production system.

Various embodiments include apparatus and methods to operate with respect to environmental measurements. Apparatus and methods include a processing unit to generate a ratio from signals measured relating to an underground environment and to determine parameters of the underground environment based on the generated ratio.

A transmitter for an acoustic logging tool includes an elongated housing, an acoustic energy generator, and a driver. The elongate housing defines a hollow interior and supports an acoustic energy generator, which includes four mutually orthogonally orientated bender bars that are electrically driveable to flex within the hollow interior in order to generate pressure-derived waves in a fluid surrounding the transmitter in use. The housing includes one or more transmissive windows via which flexing of the bender bars gives rise to propagation of one or more said waves in a said fluid. The driver electrically drives the bender bars to flex so as selectively to generate monopole, dipole, or quadrupole waves in a said fluid, with the poles of the dipole and quadrupole when generated selectively being aligned with normals to pairs of the bender bars or rotated 45° relative thereto.

In some embodiments, an apparatus and a system, as well as a method and article, may operate to substantially simultaneously measure acoustic radiation from a source in a geological formation, at each of at least two sensors in an array, over a selected time period to provide acoustic pressure measurements. Further activity may comprise locating the source at a location in the geological formation with respect to the sensors by determining acoustic intensity associated with the source, based on the acoustic pressure measurements, independent of medium sound velocity in one or more media disposed between the sensors and the source. Additional apparatus, systems, and methods are disclosed.