为了全面地描述裂缝介质的储层特征、流体性质和各向异性特征,提出了由宽方位叠前道集数据直接获取裂缝介质弹性参数和各向异性梯度参数的振幅随方位角变化(Amplitude Versus Azimuth,AVAZ)反演方法。首先推导了基于杨氏模量、泊松比和...为了全面地描述裂缝介质的储层特征、流体性质和各向异性特征,提出了由宽方位叠前道集数据直接获取裂缝介质弹性参数和各向异性梯度参数的振幅随方位角变化(Amplitude Versus Azimuth,AVAZ)反演方法。首先推导了基于杨氏模量、泊松比和各向异性梯度的各向异性AVO方程,通过与Ruger近似进行对比,分析了该方程的近似精度。然后利用实际测井资料和二维逆掩断层模型建立了不同方位角的合成叠前角度道集,对未加噪声和信噪比为3的宽方位叠前角度道集进行了AVAZ反演方法测试,结果表明,未加噪声和信噪比为3的合成宽方位叠前道集均能反演得到符合地震反演精度的杨氏模量(E),泊松比(σ)和各向异性梯度(Γ),噪声对杨氏模量的反演影响较小,不含噪声时泊松比和各向异性梯度的反演精度更高,与真实值吻合程度较高。展开更多
Fracture systems in nature are complicated. Normally vertical fractures develop in an isotropic background. However, the presence of horizontal fine layering or horizontal fractures in reservoirs makes the vertical fr...Fracture systems in nature are complicated. Normally vertical fractures develop in an isotropic background. However, the presence of horizontal fine layering or horizontal fractures in reservoirs makes the vertical fractures develop in a VTI（a transversely isotropic media with a vertical symmetry axis） background. In this case, reservoirs can be described better by using an orthorhombic medium instead of a traditional HTI（a transversely isotropic media with a horizontal symmetry axis） medium. In this paper, we focus on the fracture prediction study within an orthorhombic medium for oil-bearing reservoirs. Firstly, we simplify the reflection coefficient approximation in an orthorhombic medium. Secondly, the impact of horizontal fracturing on the reflection coefficient approximation is analyzed theoretically. Then based on that approximation, we compare and analyze the relative impact of vertical fracturing, horizontal fracturing and fluid indicative factor on traditional ellipse fitting results and the scaled B attributes. We find that scaled B attributes are more sensitive to vertical fractures, so scaled B attributes are proposed to predict vertical fractures. Finally, a test is developed to predict the fracture development intensity of an oil-bearing reservoir. The fracture development observed in cores is used to validate the study method. The findings of both theoretical analyses and practical application reveal that compared with traditional methods, this new approach has improved the prediction of fracture development intensity in oil-bearing reservoirs.展开更多
Seismic AVAZ inversion method based on an orthorhombic model can be used to invert anisotropy parameters of the Longmaxi shale gas reservoir in the Sichuan Basin..As traditional seismic inversion workfl ow does not su...Seismic AVAZ inversion method based on an orthorhombic model can be used to invert anisotropy parameters of the Longmaxi shale gas reservoir in the Sichuan Basin..As traditional seismic inversion workfl ow does not suffi ciently consider the infl uence of fracture orientation,we predict fracture orientation using the method based on the Fourier series to correct pre-stacked azimuth gathers to guarantee the accuracy of input data,and then conduct seismic AVAZ inversion based on the VTI constraints and Bayesian framework to predict anisotropy parameters of the shale gas reservoir in the study area.We further analyze the rock physical relation between anisotropy parameters and fracture compliance and mineral content for quantitative interpretation of seismic inversion results.Research results reveal that the inverted anisotropy parameters are related to P-and S-wave respectively,and thus can be used to distinguish the effect of fracture and fl uids by the joint interpretation.Meanwhile high values of anisotropy parameters correspond to high values of fracture compliance,so the anisotropy parameters can refl ect the development of fractures in reservoir.There is two sets of data from different sources,including the content of brittle mineral quartz obtained from well data and the anisotropy parameters inverted from seismic data,also show the positive correlation.This further indicates high content of brittle mineral makes fractures developing in shale reservoir and enhances seismic anisotropy of the shale reservoir.The inversion results demonstrate the characterization of fractures and brittleness for the Longmaxi shale gas reservoir in the Sichuan Basin.展开更多
文摘为了全面地描述裂缝介质的储层特征、流体性质和各向异性特征,提出了由宽方位叠前道集数据直接获取裂缝介质弹性参数和各向异性梯度参数的振幅随方位角变化(Amplitude Versus Azimuth,AVAZ)反演方法。首先推导了基于杨氏模量、泊松比和各向异性梯度的各向异性AVO方程,通过与Ruger近似进行对比,分析了该方程的近似精度。然后利用实际测井资料和二维逆掩断层模型建立了不同方位角的合成叠前角度道集,对未加噪声和信噪比为3的宽方位叠前角度道集进行了AVAZ反演方法测试,结果表明,未加噪声和信噪比为3的合成宽方位叠前道集均能反演得到符合地震反演精度的杨氏模量(E),泊松比(σ)和各向异性梯度(Γ),噪声对杨氏模量的反演影响较小,不含噪声时泊松比和各向异性梯度的反演精度更高,与真实值吻合程度较高。
基金financially supported by 973 Program (No. 2014CB239104)NSFC and Sinopec Joint Key Project (U1663207)National Key Science and Technology Project (2017ZX05049002)
文摘Fracture systems in nature are complicated. Normally vertical fractures develop in an isotropic background. However, the presence of horizontal fine layering or horizontal fractures in reservoirs makes the vertical fractures develop in a VTI（a transversely isotropic media with a vertical symmetry axis） background. In this case, reservoirs can be described better by using an orthorhombic medium instead of a traditional HTI（a transversely isotropic media with a horizontal symmetry axis） medium. In this paper, we focus on the fracture prediction study within an orthorhombic medium for oil-bearing reservoirs. Firstly, we simplify the reflection coefficient approximation in an orthorhombic medium. Secondly, the impact of horizontal fracturing on the reflection coefficient approximation is analyzed theoretically. Then based on that approximation, we compare and analyze the relative impact of vertical fracturing, horizontal fracturing and fluid indicative factor on traditional ellipse fitting results and the scaled B attributes. We find that scaled B attributes are more sensitive to vertical fractures, so scaled B attributes are proposed to predict vertical fractures. Finally, a test is developed to predict the fracture development intensity of an oil-bearing reservoir. The fracture development observed in cores is used to validate the study method. The findings of both theoretical analyses and practical application reveal that compared with traditional methods, this new approach has improved the prediction of fracture development intensity in oil-bearing reservoirs.
基金supported by the National Key S&T Special Project of China(No.2017ZX05049-002)the NSFC and Sino PEC Joint Key Project(No.U1663207)the National Natural Science Foundation of China(No.41430322)
文摘Seismic AVAZ inversion method based on an orthorhombic model can be used to invert anisotropy parameters of the Longmaxi shale gas reservoir in the Sichuan Basin..As traditional seismic inversion workfl ow does not suffi ciently consider the infl uence of fracture orientation,we predict fracture orientation using the method based on the Fourier series to correct pre-stacked azimuth gathers to guarantee the accuracy of input data,and then conduct seismic AVAZ inversion based on the VTI constraints and Bayesian framework to predict anisotropy parameters of the shale gas reservoir in the study area.We further analyze the rock physical relation between anisotropy parameters and fracture compliance and mineral content for quantitative interpretation of seismic inversion results.Research results reveal that the inverted anisotropy parameters are related to P-and S-wave respectively,and thus can be used to distinguish the effect of fracture and fl uids by the joint interpretation.Meanwhile high values of anisotropy parameters correspond to high values of fracture compliance,so the anisotropy parameters can refl ect the development of fractures in reservoir.There is two sets of data from different sources,including the content of brittle mineral quartz obtained from well data and the anisotropy parameters inverted from seismic data,also show the positive correlation.This further indicates high content of brittle mineral makes fractures developing in shale reservoir and enhances seismic anisotropy of the shale reservoir.The inversion results demonstrate the characterization of fractures and brittleness for the Longmaxi shale gas reservoir in the Sichuan Basin.
