The Geophysical Response Characteristics Of Reef And Reservoir Prediction

The reef reservoir possesses unique pore space, with a generally high porosity and permeability, it is an excellent reservoir of carbonate rock, blessed with a great potential for hydrocarbon. The reef hydrocarbon reservoir, however, ranks among one of the subtle reservoirs that are difficult to explore.The reef possesses typical characteristics of geophysical response. The seismic reflection structure of the reef is unique in the external,internal,above and the adjacent rock; it often displays abnormality at the curves of GR,dipmeter,imaging logging, and so on. To spot these typical characteristics is a major means to identify reef.With the reef hydrocarbon reservoir in the Upper Permian Changxing formations in the SYB area in Northeast Sichuan Province as the major subject of research, this thesis, based on the full understanding of the geographical background in the work area, comprehensively analyses the development scope of the reef in the Upper Permian Changxing formations over the target level in the work area by means of seismic identification. Considering the status quo of the work area - not sufficient wells and being underdeveloped, the author fully utilizes the unique characteristics of geophysical response of the reef so as to identify the abnormal scope of the reef over the three-dimensional seismic profiling one by one. On the basis of accurate level calibration of the target level, the technology of seismic waveform classification of nervous network, the technology of seismic attribute analysis and the technology of impedance inversion are utilized to conduct accurate studies over the distribution scope of the reef and discuss the profitable hydrocarbon-bearing area. With the technology of seismic waveform classification of nervous network, the relationship between the seismic facies and sedimentary facies of the Upper Permian Changxing formations in the work area is established, and the boundary of reef facies at the platform margin is clearly defined. Beginning with the analysis of the seismic attribute which has been accurately defined geologically, the author selects the four attributes - coherence cube, root mean square, main amplitude and main phase as the geological explanation of the development area of the reef. The predicted boundary of the reef is clear and the attribute of the main frequency can be used as reference for the prediction of the content of hydrocarbon in the reef. The result of the spare pulse impedance inversion and the distribution of seismic facies at the target level in the work area basically conform to the analysis results of the seismic attribute, which makes the prediction of the development area of the reef more reliable.In this paper, the above mentioned methods are utilized to reliably predict the development area of the reef in the Upper Permian Changxing formations in the SYB area in Northeast Sichuan Province,suggest favorable hydrocarbon-bearing area and provide foundational data for the arrangement of prospect and development.