In this paper, we theoretically and numerically study a combined monopole–dipole measurement mode to show its capability to overcome the issues encountered in conventional single-well imaging, i.e., the low signal-to...In this paper, we theoretically and numerically study a combined monopole–dipole measurement mode to show its capability to overcome the issues encountered in conventional single-well imaging, i.e., the low signal-to-noise ratio of the reflections and azimuth ambiguity. First, the azimuth ambiguity, which exists extensively in conventional single-well imaging, is solved with an improved imaging procedure using combined monopole–dipole logging data in addition to conventional logging data. Furthermore, we demonstrate that the direct waves propagating along the boreholes with strong energy, can be effectively eliminated with the proposed combined monopole–dipole measurement mode. The reflections are therefore predominant in the combined monopole–dipole data even before the signals are filtered; thus, the reflections' arrival times in each receiver are identified, which may help minimize the difficulties in filtering conventional logging data. The optimized processing flow of the combined measurement mode logging image is given in this paper. The proposed combined monopole–dipole measurement mode may improve the accuracy of single-well imaging.展开更多
Ultrasonic leaky Lamb waves are sensitive to defects and debonding in multilayer media. In this study, we use the finite-difference method to simulate the response of flexural waves in the presence of defects owing to...Ultrasonic leaky Lamb waves are sensitive to defects and debonding in multilayer media. In this study, we use the finite-difference method to simulate the response of flexural waves in the presence of defects owing to casing corrosion and rough fluctuations at the cement-formation interface. The ultrasonic obliquely incidence could effectively stimulate the flexural waves. The defects owing to casing corrosion change the amplitude of the early- arrival flexural wave, which gradually decrease with increasing defect thickness on the exterior walls and is the lowest when the defect length and wavelength were comparable. The scattering at the defects decreases the energy of flexural waves in the casing that leaks directly to fluids. For rough cement-formation interface, the early-arrival flexural waves do not change, whereas the late-arrival flexural waves have reduced amplitude owing to the scattering at rough interface.展开更多
The anisotropy of a geologic formation can reflect the direction of fractures and ground stress, which is an important metric that guides the exploration and development of oil and gas reservoirs. Cross-dipole acousti...The anisotropy of a geologic formation can reflect the direction of fractures and ground stress, which is an important metric that guides the exploration and development of oil and gas reservoirs. Cross-dipole acoustic logging is the main method used to detect anisotropy with borehole geophysics. In this paper, a stepwise inversion method for three anisotropy parameters in a horizontal transversely isotropic(HTI) formation is proposed, which turns one 3D operation of simultaneous inversion into three 1D operations. The scheme’s stability and reliability were tested by numerically simulated data using a f inite-difference method, and by f ield logging data. The inversion results of the simulated data show that the stepwise inversion method can stably obtain the fast shear azimuth and the anisotropy parameters in both fast and slow formations with strong and weak anisotropy, and it performed well even with noisy data. In particular, the results of the fast shear azimuth inversion were very stable and reliable. The inversion results of f ield logging data were consistent with those given by existing commercial software, which used simultaneous inversion, for both fast and slow formations. Where large difference was observed between our stepwise method and the commercial software, our analysis suggests that the fast shear azimuth of our inversion was more reasonable, which reinforces its superior performance and practicality.展开更多
This study proposes an elastic finite difference(FD)time domain method with variable grids in three-dimensional cylindrical coordinates.The calculations will diverge and become less accurate by conventional cylindrica...This study proposes an elastic finite difference(FD)time domain method with variable grids in three-dimensional cylindrical coordinates.The calculations will diverge and become less accurate by conventional cylindrical FD as the grid size gradually becomes more extensive with the increasing radius.To prevent grids from being too coarse in far fields,we compensate for the grid cell infl ation by refi ning the grid step in the azimuthal direction.The variable grid FD in the cylindrical coordinate systems has a higher effi ciency in solving acoustic logging while drilling(LWD)problems because the grid boundaries are consistent with those of the drill collar and the borehole.The proposed algorithm saves approximately 94%of the FD grids,80%of the computation time,and memory with a higher calculation accuracy than the FD on rectangular grids for the same models.We also calculate the acoustic LWD responses of the fl uid-fi lled borehole intersecting with fractures.Refl ections are generated at the fractures,which can be equivalent to an additional scattering source.The mode conversions between the collar and the Stoneley waves are revealed.The Stoneley spectra are more sensitive to the fracture.Finally,the logs in a heterogeneous formation with two refl ectors far from the borehole are modeled,and a means of estimating the azimuth of geological interfaces from refl ections is proposed.展开更多
The matrix modulus and critical porosity in rocks are two critical parameters to seismic rock physics models;however, the critical porosity is diffi cult to obtain. Based on the linear relation between the effective b...The matrix modulus and critical porosity in rocks are two critical parameters to seismic rock physics models;however, the critical porosity is diffi cult to obtain. Based on the linear relation between the effective bulk modulus and porosity, we propose a fast method for calculating the matrix modulus and critical porosity by least square fi tting of effective bulk modulus and porosity data measured in laboratory or fi eld. The proposed method is well suited for samples with wide porosity range. The calculation results accurately refl ect the differences in clay content, pressure, and saturation state. Samples with high clay content have low matrix modulus and critical porosity. The matrix modulus is independent of pressure, whereas the critical porosity increases with increasing pressure. The calculated matrix modulus for watersaturated samples is higher than that for dry rock samples.展开更多
Delineation of bed boundaries based on resistivity logging curves is important prior information for the inversion and interpretation of resistivity logging data.Traditionally,the layering algorithm mainly use the der...Delineation of bed boundaries based on resistivity logging curves is important prior information for the inversion and interpretation of resistivity logging data.Traditionally,the layering algorithm mainly use the derivatives of resistivity curves or other logging methods as reference.However,measurement error or resolution mismatch may lead to misjudgment of the boundary.In view of the shortcomings of traditional methods,this paper presents an automatic layering algorithm of array induction logging curves based on deep learning.In this algorithm,a locally connected convolution neural network is used,and the generalization ability of the network is improved by enlarging the training set,optimizing the window length and threshold,and strengthening the layering effect.Simulation and field data show the eff ectiveness of the proposed algorithm.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11574347,11374322,11134011,11734017,and 91630309)PetroChina Innovation Foundation(No.2016D-5007-0304)
文摘In this paper, we theoretically and numerically study a combined monopole–dipole measurement mode to show its capability to overcome the issues encountered in conventional single-well imaging, i.e., the low signal-to-noise ratio of the reflections and azimuth ambiguity. First, the azimuth ambiguity, which exists extensively in conventional single-well imaging, is solved with an improved imaging procedure using combined monopole–dipole logging data in addition to conventional logging data. Furthermore, we demonstrate that the direct waves propagating along the boreholes with strong energy, can be effectively eliminated with the proposed combined monopole–dipole measurement mode. The reflections are therefore predominant in the combined monopole–dipole data even before the signals are filtered; thus, the reflections' arrival times in each receiver are identified, which may help minimize the difficulties in filtering conventional logging data. The optimized processing flow of the combined measurement mode logging image is given in this paper. The proposed combined monopole–dipole measurement mode may improve the accuracy of single-well imaging.
基金supported by the Research and Development of Key Instruments and Technologies for Deep Resources Prospecting(No.ZDYZ2012-1-07)the National Natural Science Foundation of China(Nos.41204099,11134011,and 11274341)
文摘Ultrasonic leaky Lamb waves are sensitive to defects and debonding in multilayer media. In this study, we use the finite-difference method to simulate the response of flexural waves in the presence of defects owing to casing corrosion and rough fluctuations at the cement-formation interface. The ultrasonic obliquely incidence could effectively stimulate the flexural waves. The defects owing to casing corrosion change the amplitude of the early- arrival flexural wave, which gradually decrease with increasing defect thickness on the exterior walls and is the lowest when the defect length and wavelength were comparable. The scattering at the defects decreases the energy of flexural waves in the casing that leaks directly to fluids. For rough cement-formation interface, the early-arrival flexural waves do not change, whereas the late-arrival flexural waves have reduced amplitude owing to the scattering at rough interface.
基金supported by the National Natural Science Foundation of China(Grant Nos.11574347,11774373,11734017 and 91630309)the Petro China Innovation Foundation(No.2016D-5007-0304)
文摘The anisotropy of a geologic formation can reflect the direction of fractures and ground stress, which is an important metric that guides the exploration and development of oil and gas reservoirs. Cross-dipole acoustic logging is the main method used to detect anisotropy with borehole geophysics. In this paper, a stepwise inversion method for three anisotropy parameters in a horizontal transversely isotropic(HTI) formation is proposed, which turns one 3D operation of simultaneous inversion into three 1D operations. The scheme’s stability and reliability were tested by numerically simulated data using a f inite-difference method, and by f ield logging data. The inversion results of the simulated data show that the stepwise inversion method can stably obtain the fast shear azimuth and the anisotropy parameters in both fast and slow formations with strong and weak anisotropy, and it performed well even with noisy data. In particular, the results of the fast shear azimuth inversion were very stable and reliable. The inversion results of f ield logging data were consistent with those given by existing commercial software, which used simultaneous inversion, for both fast and slow formations. Where large difference was observed between our stepwise method and the commercial software, our analysis suggests that the fast shear azimuth of our inversion was more reasonable, which reinforces its superior performance and practicality.
基金supported by the National Natural Science Foundation of China(Grant Nos.12174421,11774373,11734017,and 42074215).
文摘This study proposes an elastic finite difference(FD)time domain method with variable grids in three-dimensional cylindrical coordinates.The calculations will diverge and become less accurate by conventional cylindrical FD as the grid size gradually becomes more extensive with the increasing radius.To prevent grids from being too coarse in far fields,we compensate for the grid cell infl ation by refi ning the grid step in the azimuthal direction.The variable grid FD in the cylindrical coordinate systems has a higher effi ciency in solving acoustic logging while drilling(LWD)problems because the grid boundaries are consistent with those of the drill collar and the borehole.The proposed algorithm saves approximately 94%of the FD grids,80%of the computation time,and memory with a higher calculation accuracy than the FD on rectangular grids for the same models.We also calculate the acoustic LWD responses of the fl uid-fi lled borehole intersecting with fractures.Refl ections are generated at the fractures,which can be equivalent to an additional scattering source.The mode conversions between the collar and the Stoneley waves are revealed.The Stoneley spectra are more sensitive to the fracture.Finally,the logs in a heterogeneous formation with two refl ectors far from the borehole are modeled,and a means of estimating the azimuth of geological interfaces from refl ections is proposed.
基金supported by the National Nature Science Foundation of China(Nos.11574347,11774373,11734017,91630309 and 41604123)the PetroChina Innovation Foundation(No.2016D-5007-0304)
文摘The matrix modulus and critical porosity in rocks are two critical parameters to seismic rock physics models;however, the critical porosity is diffi cult to obtain. Based on the linear relation between the effective bulk modulus and porosity, we propose a fast method for calculating the matrix modulus and critical porosity by least square fi tting of effective bulk modulus and porosity data measured in laboratory or fi eld. The proposed method is well suited for samples with wide porosity range. The calculation results accurately refl ect the differences in clay content, pressure, and saturation state. Samples with high clay content have low matrix modulus and critical porosity. The matrix modulus is independent of pressure, whereas the critical porosity increases with increasing pressure. The calculated matrix modulus for watersaturated samples is higher than that for dry rock samples.
基金the National Nature Science Foundation of China(No.41604123)。
文摘Delineation of bed boundaries based on resistivity logging curves is important prior information for the inversion and interpretation of resistivity logging data.Traditionally,the layering algorithm mainly use the derivatives of resistivity curves or other logging methods as reference.However,measurement error or resolution mismatch may lead to misjudgment of the boundary.In view of the shortcomings of traditional methods,this paper presents an automatic layering algorithm of array induction logging curves based on deep learning.In this algorithm,a locally connected convolution neural network is used,and the generalization ability of the network is improved by enlarging the training set,optimizing the window length and threshold,and strengthening the layering effect.Simulation and field data show the eff ectiveness of the proposed algorithm.
