Search

Due to the instability of extracting elastic parameters from conventional elastic impedance variation with incident angle (EVA) pre-stack inversion and the fact that single-trace inversion does not consider the correlation between seismic traces and the lateral continuity of inversion results. An anisotropic total variation multitrace inversion method based on the L P norm constraint is proposed on the basis of EVA inversion. In this paper, the L P norm is used as the regularization constraint, the longitudinal and transverse difference operators are introduced, and the alternating direction multiplier algorithm and the 2D Sylvester equation solver algorithm are used as inversion algorithms to achieve a multitrace inversion of the elastic parameters. The feasibility of the method proposed in this paper is verified by making full use of the advantages of both methods and conducting trial calculations on some blocks of the Marmousi2 model. The method was further validated by applying it to actual data from marine shales of the Longmaxi-Wufeng Formation in the southern Sichuan Basin. The inversion results were validated using a combination of brittleness indices and microseismic monitoring to confirm the feasibility of the method in this paper. •Proposed anisotropic total variation multitrace inversion method based on Lp norm. •Multitrace inversions enhance the lateral continuity of inversion results. •Different noise tests demonstrate the noise immunity of the inversion method. •Validation of the method with brittleness index and microseismic events. [ABSTRACT FROM AUTHOR]

Due to the instability of extracting elastic parameters from conventional elastic impedance variation with incident angle (EVA) pre-stack inversion and the fact that single-trace inversion does not consider the correlation between seismic traces and the lateral continuity of inversion results. An anisotropic total variation multitrace inversion method based on the L P norm constraint is proposed on the basis of EVA inversion. In this paper, the L P norm is used as the regularization constraint, the longitudinal and transverse difference operators are introduced, and the alternating direction multiplier algorithm and the 2D Sylvester equation solver algorithm are used as inversion algorithms to achieve a multitrace inversion of the elastic parameters. The feasibility of the method proposed in this paper is verified by making full use of the advantages of both methods and conducting trial calculations on some blocks of the Marmousi2 model. The method was further validated by applying it to actual data from marine shales of the Longmaxi-Wufeng Formation in the southern Sichuan Basin. The inversion results were validated using a combination of brittleness indices and microseismic monitoring to confirm the feasibility of the method in this paper. •Proposed anisotropic total variation multitrace inversion method based on Lp norm. •Multitrace inversions enhance the lateral continuity of inversion results. •Different noise tests demonstrate the noise immunity of the inversion method. •Validation of the method with brittleness index and microseismic events. [ABSTRACT FROM AUTHOR]

The lamellation fractures in marine shales are important to the accumulation and preservation of shale gas, whose characteristics and controlling factors are still unclear. This paper focus on the characteristics descriptions and controlling factor analyses based on core observations, thin sections, and scanning electron microscope (SEM) experiments. The marine shales of Paleozoic Wufeng Formation and Longmaxi Formation in the Fuling Area of Eastern Sichuan Basin are taken as an instance. The lamellation fractures are occurring along the direction of the lamellations, partially of them curved, bifurcated, and converged. The apertures of fractures typically range from 1 to 500 μm. Only a few (<1%) lamellation fractures are filled with quartz, calcite, pyrite, and bitumen. After a series of analyses, developments of lamellation fractures are controlled by total organic carbon (TOC), brittle minerals, laminae, and pyrite. (1) The organic matters control the formation and evolution of lamellation fractures by generating gas and resulting in overpressure. An increase in the TOC content of 1% can increase the lamellation fracture density by 0.26 cm-1. (2) Brittle minerals, especially authigenic quartz, is also an important controlling factor to the development of lamellation fractures. When BI increases by 10%, the lamellation fracture density increases by 19%. (3) Besides, siliceous and carbonate laminae in the shale are more suitable for lamellation fractures to develop. When the laminae density is smaller than 4 cm−1, it is easier to develop lamellation fractures with higher laminae density. However, too densely-distributed laminae will suppress the formation of lamellation fractures. (4) Higher pyrite content is good for the development of lamellation fractures. Lamellation fracture density will increase by 9%, with pyrite content increased by 1%. For the shale at the bottom of the Wufeng Formation - Longmaxi Formation, lamellation fractures develop extensively due to the high TOC and pyrite content, great brittleness, and moderate laminae density. The density of lamellation fractures decreases from the bottom to the top. • Quantitative characterize about development characteristics of the lamellation fractures. • The lamellation fractures is controlled by brittle mineral, TOC, laminae and pyrite. • TOC is the main one that affects the development of lamellation fractures. • Clarify vertical distribution characteristic of lamellation fractures in the Wufeng-longmaxi Fm. [ABSTRACT FROM AUTHOR]