Seismic amplitude variation with azimuths has been proved to be an important tool in characterizing fracture distribution and orientation of hydrocarbon reservoir. However, questions remain about the feasibility and robustness of seismic characterization for fracture system, especially on the horizontal or vertical resolution and orientation of fractures. This study focus on a pragmatic and robust method in the estimation of fracture orientation assuming a single set of aligned fractures. Young's modulus in the direction of fracture orientation is known to be bigger than that in the perpendicular direction of fracture orientation, which helps to solve the problem of the ambiguity in fracture orientation estimation by using the variation of AVO (Amplitude variation with offsets) gradients with azimuths. The relationship between Young's modulus and fracture density and orientation from the point of rock physics is analyzed and Young's modulus changes regularly with the variation of incident angles and azimuths and the changing track of Young's modulus varying with azimuth is a cosine curve when the incident angle is fixed. With the increase of fracture density, the amplitude of variation of Young's modulus increases. Furthermore, the method of Young's modulus variation with azimuth to predict the fracture orientation is proposed. It contains two steps, Young's modulus inversion for different azimuths of pre-stack seismic data and the ellipse fitting of the Young's moduli in different azimuths with least-square algorithm. Finally, the synthetic and real data examples demonstrated the advantage and robustness of proposed method in fracture orientation estimation. Compared to the conventional methods with AVO gradients, the direction of long axis of the fitting ellipse of the Young's modulus in different azimuths indicates the fracture orientation without ambiguity.
Presentation Date: Tuesday, September 26, 2017
Start Time: 3:55 PM
Location: Exhibit Hall C, E-P Station 1
Presentation Type: EPOSTER
