A system and method are disclosed for determining an internal multiples-free seismic dataset. The method includes obtaining a seismic dataset, wherein the seismic dataset comprises a plurality of space-time gathers, determining a first truncation operator, wherein the first truncation operator mutes samples of each trace after a first predetermined intercept time in a transform domain, and determining a second truncation operator, wherein the second truncation operator mutes samples of each trace before a second predetermined intercept time in the transform domain. The method further includes applying Marchenko internal multiple attenuation on the seismic dataset using the first and second truncation operators to determine the internal multiples-free seismic dataset.

Systems, devices, and methods for evaluating an earth formation intersected by a borehole using signals produced at a plurality of borehole depths by an ultrasonic transducer in the borehole, the signals produced by the transducer including ringdown signals from the ultrasonic transducer and echo signals from a wall of the borehole from a plurality of azimuthal orientations. Methods include using peak amplitude values and arrival time values from the signals to construct a background modulation template corresponding to at least one depth; estimating, for each respective depth of the plurality of borehole depths, an azimuthally varying interference pattern predominantly resulting from a ringdown signal for each respective depth by mapping the modulation template to arrival time values corresponding to the respective depth; and subtracting, for each respective depth, the estimated varying interference pattern from the peak amplitude values corresponding to the respective depth to generate adjusted peak amplitudes.

A system and method are provided for creating interior seismic data between measurements of actual seismic data. The interior seismic data may be created using processes for approximating or constructing seismic data between times the actual seismic data is sampled. In some aspects, the interior seismic data may be approximated by determining a rate of change in the seismic data between at least two measurements of seismic data over time. In other aspects, the interior seismic data may be created by constructing an intermediate state of the formation between the times corresponding to at least two measurements of the seismic data based on a trend associated with the measurements. In additional aspects, a Gaussian white noise may be applied to the measurements to yield an array of equally probable predictions for the intermediate state of the property.

A memory-efficient Q-RTM computer method and apparatus for imaging seismic data is described. A seismic image may be formed from a memory-efficient Q-RTM module utilizing received attenuated seismic data. Seismic data is processed by the memory-efficient Q-RTM module to compensate for amplitude attenuation and phase velocity dispersion simultaneously during back-propagation in RTM. A negative quality factor, Q, is obtained by modifying the wave equation to compensate for amplitude attenuation. One or more dispersion optimization terms introduced to a wave equation for compensation of Q effects on the phase, solved by a finite difference algorithm, compensate for phase velocity change and further adjust amplitude attenuation compensation.

Seismic node systems can be configured for acquiring seismic sensor data with an array of seismic receivers or nodes deployable in a survey area, each receiver or node having a seismic sensor for acquiring the seismic sensor data, a clock, a controller and local memory. The seismic sensor can data characterize a seismic wavefield proximate the seismic receivers in the survey area. Quality control data can be generated based on the seismic sensor data and associated timing information provided by the respective clock, and incorporated into a seismic data flow for recording in the local memory.

Techniques for estimating and visually presenting formation slowness are disclosed herein. The techniques include receiving acoustic signal responses from adjacent formations at a plurality of depths in a borehole environment, mapping a distribution of the acoustic signal responses at each depth according to slowness and a frequency values, determining at least one confidence interval to define a coherence threshold for the distribution of the acoustic signal responses at each depth, generating a variable density log for each depth based on the distribution of acoustic signals responses that satisfy the confidence interval for one or more frequency ranges, determining a formation slowness value for each depth based on the variable density log for the each depth, and presenting a semblance map that includes a slowness axis, a depth axis, the formation slowness value for each depth, and at least a portion of the distribution of acoustic signal responses at each depth.

Disclosed are systems and methods for high precision acoustic logging processing for compressional and shear slowness. The method comprises measuring, by a sonic logging tool, sonic data associated with a formation within a borehole, attempting a detection of a first arrival within the sonic data determining whether the attempted detection of the first arrival is accurate, and in response to an accurate detection of the first arrival determining a travel time of the first arrival, generating a coherence map including the first arrival, and determining, based on the coherence map, a characteristic of the formation.

Target objects having undulating surfaces are simulated using different triangle mesh sizes to improve processing performance. To perform the simulation, a target object is generated using a triangle mesh formed by a plurality of triangles. The target object has an X, Y, and Z direction, wherein the Z direction is perpendicular to an X-Y plane of the target object. The undulating surface on the target object is generated using a Z value in the Z direction.

Methods and apparatus for performing formation evaluation in a borehole intersecting an earth formation. Methods may include exciting at a first borehole depth at least one critical refraction wave by steering an acoustic beam transmitted by at least one ultrasonic transmitter to an interface in the formation to intercept the interface at a critical angle; receiving an acoustic signal comprising critical refraction wave data at a logging tool in the borehole; and obtaining a wave property measurement from the critical refraction wave data. The interface may be the borehole wall in an open-hole well or behind casing. Methods include using ultrasonic transmitter(s) to generate the plurality of acoustic beams, identifying critical refraction wave data within the response signal corresponding to the at least one critical refraction wave, and obtaining the wave property measurement from the critical refraction wave data.

A system and method for determining a set of first breaks of a seismic dataset are disclosed, the method including obtaining the seismic dataset composed of a plurality of seismic traces and a provisional first break for each seismic trace. The method further includes selecting a plurality of proximal picks for each seismic trace, determining a near-offset pick for each seismic trace starting with shortest offset and sequentially selecting traces in order of increasing offset, and determining a far-offset pick for each seismic trace starting with the farthest offset and sequentially selecting traces in order of decreasing offset. The method further includes determining a set of coincident picks based on the near-offset and the far-offset picks for each seismic trace, fitting a curve to the set of coincident picks, and determining the set of first breaks of the seismic dataset from the curve.