For real-time inversion and fast reconstruction of formation true resistivity, the forward modeling of electromagnetic wave logging while drilling is usually based on the transversely isotropic formation model with ve...For real-time inversion and fast reconstruction of formation true resistivity, the forward modeling of electromagnetic wave logging while drilling is usually based on the transversely isotropic formation model with vertical symmetry axis(VTI medium), but it only considers the horizontal and vertical resistivity. It has certain limitation during practical application. This paper presents a forward calculation method of electromagnetic wave logging while drilling in transversely isotropic(TTI) strata with inclined symmetry axis based on the Dyadic Green’s function. Anisotropic angle and azimuth are used to characterize TTI formation. The proposed algorithm is verified by numerical examples, the half-space electromagnetic wave reflection and transmission characteristics with different media are analyzed, and the necessity to use the new algorithm is pointed out. Numerical simulation also shows that there exist a critical borehole dip and critical anisotropic angle in TTI formation. Electromagnetic wave logging while drilling responses follows opposite rule before and after these two critical angles. Besides, the 'horns' at the interface are not only related to well deviation, resistivity contrast, but also related to anisotropic angle and anisotropic azimuth.展开更多
Electromagnetic logging while drilling(LWD)is one of the key technologies of the geosteering and formation evaluation for high-angle and horizontal wells.In this paper,we solve the dipole source-generated magnetic/ele...Electromagnetic logging while drilling(LWD)is one of the key technologies of the geosteering and formation evaluation for high-angle and horizontal wells.In this paper,we solve the dipole source-generated magnetic/electric fields in 2D formations efficiently by the 2.5D finite diff erence method.Particularly,by leveraging the field’s rapid attenuation in spectral domain,we propose truncated Gauss–Hermite quadrature,which is several tens of times faster than traditional inverse fast Fourier transform.By applying the algorithm to the LWD modeling under complex formations,e.g.,folds,fault and sandstone pinch-outs,we analyze the feasibility of the dimension reduction from 2D to 1D.For the formations with smooth lateral changes,like folds,the simplified 1D model’s results agree well with the true responses,which indicate that the 1D simplification with sliding window is feasible.However,for the formation structures with drastic rock properties changes and sharp boundaries,for instance,faults and sandstone pinch-outs,the simplified 1D model will lead to large errors and,therefore,2.5D algorithms should be applied to ensure the accuracy.展开更多
Tool waves, also named collar waves, propagating along the drill collars in acoustic logging while drilling （ALWD）, strongly interfere with the needed P- and S-waves of a penetrated formation, which is a key issue i...Tool waves, also named collar waves, propagating along the drill collars in acoustic logging while drilling （ALWD）, strongly interfere with the needed P- and S-waves of a penetrated formation, which is a key issue in picking up formation P- and S-wave velocities. Previous studies on physical insulation for the collar waves designed on the collar between the source and the receiver sections did not bring to a satisfactory solution. In this paper, we investigate the propagation features of collar waves in different models. It is confirmed that there exists an indirect collar wave in the synthetic full waves due to the coupling between the drill collar and the borehole, even there is a perfect isolator between the source and the receiver. The direct collar waves propagating all along the tool and the indirect ones produced by echoes from the borehole wall are summarized as the generalized collar waves. Further analyses show that the indirect collar waves could be relatively strong in the full wave data. This is why the collar waves cannot be eliminated with satisfactory effect in many cases by designing the physical isolators carved on the tool.展开更多
基金Supported by the National Natural Science Foundation of China(41474100,41574118)
文摘For real-time inversion and fast reconstruction of formation true resistivity, the forward modeling of electromagnetic wave logging while drilling is usually based on the transversely isotropic formation model with vertical symmetry axis(VTI medium), but it only considers the horizontal and vertical resistivity. It has certain limitation during practical application. This paper presents a forward calculation method of electromagnetic wave logging while drilling in transversely isotropic(TTI) strata with inclined symmetry axis based on the Dyadic Green’s function. Anisotropic angle and azimuth are used to characterize TTI formation. The proposed algorithm is verified by numerical examples, the half-space electromagnetic wave reflection and transmission characteristics with different media are analyzed, and the necessity to use the new algorithm is pointed out. Numerical simulation also shows that there exist a critical borehole dip and critical anisotropic angle in TTI formation. Electromagnetic wave logging while drilling responses follows opposite rule before and after these two critical angles. Besides, the 'horns' at the interface are not only related to well deviation, resistivity contrast, but also related to anisotropic angle and anisotropic azimuth.
基金the National Natural Science Foundation of China (41674131,41574118,41974146,41904109)the Fundamental Research Funds for the Central Universities (17CX06041,17CX06044)the China National Science and Technology Major Project (2016ZX05007-004,2017ZX05072-002)
文摘Electromagnetic logging while drilling(LWD)is one of the key technologies of the geosteering and formation evaluation for high-angle and horizontal wells.In this paper,we solve the dipole source-generated magnetic/electric fields in 2D formations efficiently by the 2.5D finite diff erence method.Particularly,by leveraging the field’s rapid attenuation in spectral domain,we propose truncated Gauss–Hermite quadrature,which is several tens of times faster than traditional inverse fast Fourier transform.By applying the algorithm to the LWD modeling under complex formations,e.g.,folds,fault and sandstone pinch-outs,we analyze the feasibility of the dimension reduction from 2D to 1D.For the formations with smooth lateral changes,like folds,the simplified 1D model’s results agree well with the true responses,which indicate that the 1D simplification with sliding window is feasible.However,for the formation structures with drastic rock properties changes and sharp boundaries,for instance,faults and sandstone pinch-outs,the simplified 1D model will lead to large errors and,therefore,2.5D algorithms should be applied to ensure the accuracy.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11134011 and 11374322)the Foresight Research Project,Institute of Acoustics,Chinese Academy of Sciences
文摘Tool waves, also named collar waves, propagating along the drill collars in acoustic logging while drilling （ALWD）, strongly interfere with the needed P- and S-waves of a penetrated formation, which is a key issue in picking up formation P- and S-wave velocities. Previous studies on physical insulation for the collar waves designed on the collar between the source and the receiver sections did not bring to a satisfactory solution. In this paper, we investigate the propagation features of collar waves in different models. It is confirmed that there exists an indirect collar wave in the synthetic full waves due to the coupling between the drill collar and the borehole, even there is a perfect isolator between the source and the receiver. The direct collar waves propagating all along the tool and the indirect ones produced by echoes from the borehole wall are summarized as the generalized collar waves. Further analyses show that the indirect collar waves could be relatively strong in the full wave data. This is why the collar waves cannot be eliminated with satisfactory effect in many cases by designing the physical isolators carved on the tool.
基金supported by the Forward-looking Fundamental Major Science and Technology Project of"14th Five-Year Plan"of China National Petroleum Corporation,"Research on Horizontal Well Logging Processing Technology" (Grant No.2021DJ4001)the PetroChina Innovation Foundation (Grant No.2020D-5007-0304)the Fundamental Research Funds for the Central Universities (Grant Nos.21CX06005A and 22CX01001A-2).
