Existing seismic prediction methods struggle to effectively discriminate between fluids in tight gas reservoirs,such as those in the Sulige gas field in the Ordos Basin,where porosity and permeability are extremely lo...Existing seismic prediction methods struggle to effectively discriminate between fluids in tight gas reservoirs,such as those in the Sulige gas field in the Ordos Basin,where porosity and permeability are extremely low and the relationship between gas and water is complicated.In this paper,we have proposed a comprehensive seismic fluid identification method that combines ray-path elastic impedance(REI)inversion with fluid substitution for tight reservoirs.This approach is grounded in geophysical theory,forward modeling,and real data applications.We used geophysics experiments in tight gas reservoirs to determine that Brie's model is better suited to calculate the elastic parameters of mixed fluids than the conventional Wood’s model.This yielded a more reasonable and accurate fluid substitution model for tight gas reservoirs.We developed a forward model and carried out inversion of REI.which reduced the non-uniqueness problem that has plagued elastic impedance inversion in the angle domain.Our well logging forward model in the ray-path domain with different fluid saturations based on a fluid substitution model proved that REI identifies fluids more accurately when the ray parameters are large.The distribution of gas saturation can be distinguished from the crossplot of REI(p=0.10)and porosity.The inverted ray-path elastic impedance profile was further used to predict the porosity and gas saturation profile.Our new method achieved good results in the application of 2D seismic data in the western Sulige gas field.展开更多
The three dimensional ray-path equation considering the effect of the horizontal gradient of the ionospheric electron density is obtained. By integrating in upgoing and downgoing stage, the point on the raypath can be...The three dimensional ray-path equation considering the effect of the horizontal gradient of the ionospheric electron density is obtained. By integrating in upgoing and downgoing stage, the point on the raypath can be determined and the propagation channel in HF radio telecommunication may be recknoed and predicted. Considering the effect of the electron density slope the ray-path is asymmetric about the reflecting point, and the wave is no longer in the great circle determined by the original wave vector. The group path and the phase path can also be solved.展开更多
A new seismic ray-tracing method is put forward based on parabolic travel-time interpolation(PTI) method, which is more accurate than the linear travel-time interpolation (LTI) method. Both PTI method and LTI method a...A new seismic ray-tracing method is put forward based on parabolic travel-time interpolation(PTI) method, which is more accurate than the linear travel-time interpolation (LTI) method. Both PTI method and LTI method are used to compute seismic travel-time and ray-path in a 2-D grid cell model. Firstly, some basic concepts are introduced. The calculations of travel-time and ray-path are carried out only at cell boundaries. So, the ray-path is always straight in the same cells with uniform velocity. Two steps are applied in PTI and LTI method, step 1 computes travel-time and step 2 traces ray-path. Then, the derivation of LTI formulas is described. Because of the presence of refraction wave in shot cell, the formula aiming at shot cell is also derived. Finally, PTI method is presented. The calculation of PTI method is more complex than that of LTI method, but the error is limited. The results of numerical model show that PTI method can trace ray-path more accurately and efficiently than LTI method does.展开更多
A new method based on Huygens' principle and Fermat's principle is presented to calculate seismic traveltime and ray-paths in this paper. The algorithm can be easily understood and programmed, and can be appli...A new method based on Huygens' principle and Fermat's principle is presented to calculate seismic traveltime and ray-paths in this paper. The algorithm can be easily understood and programmed, and can be applied to heteroge neous media in order to eliminate its disadvantage of slowness, we have improved the basic algorithm to speed its calculation to practical stage without the loss of its accuracy.展开更多
基金supported by the National Science and Technology Major Project(No.2016ZX05050 and 2017ZX05069)CNPC Major Technology Special Project(No.2016E-0503)
文摘Existing seismic prediction methods struggle to effectively discriminate between fluids in tight gas reservoirs,such as those in the Sulige gas field in the Ordos Basin,where porosity and permeability are extremely low and the relationship between gas and water is complicated.In this paper,we have proposed a comprehensive seismic fluid identification method that combines ray-path elastic impedance(REI)inversion with fluid substitution for tight reservoirs.This approach is grounded in geophysical theory,forward modeling,and real data applications.We used geophysics experiments in tight gas reservoirs to determine that Brie's model is better suited to calculate the elastic parameters of mixed fluids than the conventional Wood’s model.This yielded a more reasonable and accurate fluid substitution model for tight gas reservoirs.We developed a forward model and carried out inversion of REI.which reduced the non-uniqueness problem that has plagued elastic impedance inversion in the angle domain.Our well logging forward model in the ray-path domain with different fluid saturations based on a fluid substitution model proved that REI identifies fluids more accurately when the ray parameters are large.The distribution of gas saturation can be distinguished from the crossplot of REI(p=0.10)and porosity.The inverted ray-path elastic impedance profile was further used to predict the porosity and gas saturation profile.Our new method achieved good results in the application of 2D seismic data in the western Sulige gas field.
文摘The three dimensional ray-path equation considering the effect of the horizontal gradient of the ionospheric electron density is obtained. By integrating in upgoing and downgoing stage, the point on the raypath can be determined and the propagation channel in HF radio telecommunication may be recknoed and predicted. Considering the effect of the electron density slope the ray-path is asymmetric about the reflecting point, and the wave is no longer in the great circle determined by the original wave vector. The group path and the phase path can also be solved.
文摘A new seismic ray-tracing method is put forward based on parabolic travel-time interpolation(PTI) method, which is more accurate than the linear travel-time interpolation (LTI) method. Both PTI method and LTI method are used to compute seismic travel-time and ray-path in a 2-D grid cell model. Firstly, some basic concepts are introduced. The calculations of travel-time and ray-path are carried out only at cell boundaries. So, the ray-path is always straight in the same cells with uniform velocity. Two steps are applied in PTI and LTI method, step 1 computes travel-time and step 2 traces ray-path. Then, the derivation of LTI formulas is described. Because of the presence of refraction wave in shot cell, the formula aiming at shot cell is also derived. Finally, PTI method is presented. The calculation of PTI method is more complex than that of LTI method, but the error is limited. The results of numerical model show that PTI method can trace ray-path more accurately and efficiently than LTI method does.
文摘A new method based on Huygens' principle and Fermat's principle is presented to calculate seismic traveltime and ray-paths in this paper. The algorithm can be easily understood and programmed, and can be applied to heteroge neous media in order to eliminate its disadvantage of slowness, we have improved the basic algorithm to speed its calculation to practical stage without the loss of its accuracy.
