A computer system receives a post-stack time-domain image having a first spectrum and representing one or more subsurface structures. The computer system reconstructs an increased-frequency version of the post-stack time-domain image using L0-constrained inversion and a least-squares mismatch ratio. The increased-frequency version of the post-stack time-domain image includes structural artifacts. The computer system removes the structural artifacts from the increased-frequency version of the post-stack time-domain image using singular value decomposition. The computer system combines the increased-frequency version of the post-stack time-domain image with the post-stack time-domain image using a weighting function. The computer system generates a combined version of the increased-frequency version of the post-stack time-domain image and the post-stack time-domain image. The combined version represents the one or more subsurface structures and has a second spectrum broader than the first spectrum.

Pipe]parameter determinations from electromagnetic logs can be improved, in accordance with various embodiments, by weighting signals with frequencies below a threshold associated with resolution degradation lower than signals with frequencies above the threshold. The threshold frequency may be determined based on a spatial resolution associated with the logging tool and a logging speed. Further embodiments are described.

A method that includes transforming a relative amplitude preserved 3D seismic volume acquired in the time-domain into a plurality of isofrequency volumes, extracting from the plurality of isofrequency volumes a first isofrequency spectral amplitude volume and a second isofrequency spectral amplitude volume. The method further includes determining an attribute volume from the two isofrequency spectral amplitude volumes, and determining a presence of gas in a subterranean region of interest based on the attribute volume.

A computer-implemented method and system implementing the method, are disclosed for computing small cave recognition models, using seismic reflection data. User inputs and earth-model data are obtained over points of incidence of a survey region, at various angles of incidence. Various models are then computed that serve for cave identification and take part in preliminary seismic exploration and reservoir characterization. Therefore, the attributes developed by the computer-implemented method and system serve as indicators of low velocity and density cave recognition which are capable of separating the cave events from the normal layer events; identifying caves with size larger than half to one wavelength of the dominant signal; and identifying cave diffractions from caves that contain a local maximal/minimal at around nine degrees in amplitude versus angle models.

A computer-implemented method and system implementing the method, are disclosed for computing small cave recognition models, using seismic reflection data. User inputs and earth-model data are obtained over points of incidence of a survey region, at various angles of incidence. Various models are then computed that serve for cave identification and take part in preliminary seismic exploration and reservoir characterization. Therefore, the attributes developed by the computer-implemented method and system serve as indicators of low velocity and density cave recognition which are capable of separating the cave events from the normal layer events; identifying caves with size larger than half to one wavelength of the dominant signal; and identifying cave diffractions from caves that contain a local maximal/minimal at around nine degrees in amplitude versus angle models.

A computer system receives a post-stack time-domain image having a first spectrum and representing one or more subsurface structures. The computer system reconstructs an increased-frequency version of the post-stack time-domain image using L0-constrained inversion and a least-squares mismatch ratio. The increased-frequency version of the post-stack time-domain image includes structural artifacts. The computer system removes the structural artifacts from the increased-frequency version of the post-stack time-domain image using singular value decomposition. The computer system combines the increased-frequency version of the post-stack time-domain image with the post-stack time-domain image using a weighting function. The computer system generates a combined version of the increased-frequency version of the post-stack time-domain image and the post-stack time-domain image. The combined version represents the one or more subsurface structures and has a second spectrum broader than the first spectrum.

A system for estimating a property of a region of interest includes an acoustic measurement device including a transmitter configured to emit an acoustic signal having at least one selected frequency configured to penetrate a surface of a borehole in an earth formation and produce internal diffuse backscatter from earth formation material behind the surface and within the region of interest, and a receiver configured to detect return signals from the region of interest and generate return signal data. The system also includes a processing device configured to receive the return signal data, process the return signal data to identify internal diffuse backscatter data indicative of the internal diffuse backscatter, calculate one or more characteristics of the internal diffuse backscatter, and estimate a property of the region of interest based on the one or more characteristics of the internal diffuse backscatter.

The instant invention relates to a method for noise reduction from a magnetic resonance sounding (MRS) oscillating signal, and more particularly, to a data processing method for reducing random noise contained in MRS oscillating signal based on joint algorithm principles of EMD and TFPF. A MRS oscillating signal is decomposed into different eigen-mode components by using decomposition characteristic of EMD algorithm; then a signal-dominated eigen-mode component is encoded as an instantaneous frequency of an analytical signal of unit amplitude using TFPF algorithm; and random noise is suppressed with the characteristics that the time-frequency distribution of the analytical signal is concentrated along with the instantaneous frequency. The method requires fewer filtering constraints and is simple to operate without need of designing a filtering interval in the time-frequency domain, and has good adaptability to the MRS oscillating signal with a low signal-noise-ratio.

Waves from cement bond logging with a sonic logging-while-drilling tool (LWD-CBL) are often contaminated with tool waves and may yield biased CBL amplitudes. The disclosed LWD-CBL wave processing corrects the first echo amplitudes of LWD-CBL before calculating the BI. The LWD-CBL wave processing calculates a tool wave amplitude and a phase angle difference as the difference of the phases between the tool waves and casing waves. The tool waves are then used to correct the LWD-CBL casing wave amplitude and remove errors introduced from tool waves. In conjunction with the sets of operations described, the LWD-CBL wave processing also include array preprocessing operations. Array preprocessing may employ variation of bandpass filtering and frequency-wavenumber (F-K) filtering operations to suppress tool wave.

A method for use in seismic exploration comprises: accessing a set of seismic data representative of a subterranean geological formation and a subsurface attribute model of the subterranean geological formation; performing a wavefield extrapolation on the seismic data in the subsurface attribute model; applying the time-shift extended imaging condition to the extrapolated wavefields; forming shot-indexed, time shift gathers for each image pixel of the subsurface attribute model from the conditioned extrapolated wavefields; adaptively focusing the gathers; and stacking the adaptively focused gathers; and imaging the subterranean geological formation from the stacked, adaptively focused gathers. The method may, in some aspects, be realized by a computing apparatus programmed to perform the method or as a set of instructions encoded on a non-transitory program storage medium that, when executed by a computing apparatus, perform the method.