The Review Of The Diffracton Wave Field About Fractured-vuggy Carbonate Reservoir

At present,the degree of oil and gas exploration is constantly deepening,and the future development direction is mainly based on unconventional oil and gas exploration and remaining oil exploration.In China,carbonate reservoirs are rich in oil and gas resources,and have made great achievements in blocks such as Sichuan basin and Tarim Basin.The carbonate reservoirs in China are mostly fractured vuggy reservoirs,which are characterized by deep burial and strong spatial heterogeneity.In seismic exploration,fractured-vuggy carbonate reservoirs are weakly reflected in seismic section.The weak reflection characteristic can be attributed to the diffraction imaging in the seismic wave field,and its energy is obviously weaker than the reflected wave.Therefore,it is very necessary to separate the diffraction wave and analyze the corresponding relationship between the response characteristics of the diffraction wave and the fractured-vuggy carbonate reservoir element.The purpose of this paper is to study how the diffraction wave represents the fracture cavity reservoir of carbonate rock.For that reason,the first step is summarizing the composition,reservoir space characteristics and reservoir types of carbonate rocks.As a kind of significant sedimentary rocks,various pores in carbonate reservoirs are oil and gas migration channels and reservoir spaces.During the formation of the pores,they are different in size,shape,characteristics and development degree because of the multiple diagenesis,and then influenced by the tectonic action.The result is the dissolving holes,karst caves and cracks of different scales,and the three are composed of carbonate reservoirs.There are great differences between different reservoirs in terms of size and spatial form.Then,the definition,dynamics and kinematics characteristics of diffraction wave are analyzed and compared with the reflection wave.The diffraction wave has great effect on the interfaces with large curvature,such as the edge of the fault,the point of the geological tip and the reservoir of the carbonate hole,but the energy is less than the reflected wave,and the information contained in the section is not fully utilized.The diffraction wave and the reflected wave are quite different in the common offset gather,so that separating the diffracted wave from the full wave field is feasible.In this study,the Tahe oilfield and Shun Bei oil and gas field in Tarim Basin are the target blocks.By collecting geological data and analyzing seismic and log data,the model of karst cave type and vertical fracture zone are designed.Then,the seismic wave propagation is simulated in the geological model,and the corresponding wave field records are obtained.In the wave field recording,the separation of diffracted waves was tested.And the method about separation of diffracted wave in prestack section was used.Then in the karst cave model,the structure,the scale and the filler are set the variables,and the faults model takes the fracture density and the broken length as the variable.The imaging characteristics in the diffraction wave section were analyzed,and the imaging characteristics of the diffraction wave on the karst cave and the faults model were summarized with the technology of attribute analysis.The imaging of fracture and cavity units on the section is larger than the actual scale,and the phase,frequency and amplitude attributes can identify the filling degree and scale better.