The Study Of Seismic Detection And Fluid Identification In Reef And Bank Reservoir In Northeast Sichuan

Biological reef and bank reservoirs are highly respected by geophysicists for their much more trap, better storage, well hydrocarbon, high production and so on. From the simples definition, structure, classification, developmental mechanism, sedimentary context and depositional environment of the carbonate rock to the reservoir characterization, seismic reflective feature, log response, reservoir identification and prediction, all of which are the important content in study of the oil and gas exploration. In china, Sichuan Basin is a large-scale oil and gas superimposed basin, in which the sedimentary covers are fully developed. Permian Changxing Formation and lower Triassic Feixianguan Formation is marine sediments in the northeast of Sichuan basin, in which the rocks are mainly carbonate rocks.In this paper, based on fully collect and research of the seismic, geology, logging, drilling, etc of SYB area in the northeast of Sichuan, we calibrate the formation and make the t0 and time thickness map, and we divide the seismic facies, form this we determine that the tableland edge of the reef and bank are the main area of the reservoir.In this paper, the seismic detection and fluid identification of the reef and bank reservoirs in SYB area is the main study. Reef and bank reservoirs in this region are hidden reservoirs of oil and gas, which is difficult to forecast, the success rate of drilling is low, seismic detection and fluid identification methods are in a period of development. In this study, we begin with the definition and basic characteristics of reef and bank, of them we give a detailed description that include the concept of reef and bank, classification, and the difference between the reef and bank. We make a deep study in the characteristics of the seismic response to the reef and bank reservoir, sum up the seismic reflection character of the reef in external, internal, at the top, bottom and border. Compared with the reef, the characteristics of the seismic response of the bank are not particularly evident, but we study carefully on it here. We make a analysis of the method that identify reef and bank from the seismic response in two-dimensional and three-dimensional. We illustrate the principles and examples of seismic facies, and give a number of typical profile that are also conductive to identify the character of the reef and bank.We illustrate the location of work area, the history of tectonic development, formation characteristics, sedimentary facies and depositional pattern in details, and the seismic data, geological, drilling, logging of this work area are analyzed. Based on this, the reef and bank reservoirs are studied over the seismic detection and fluid identification.When the reservoir is filled with oil and gas, the seismic wave velocity, formation density, porosity, acoustic impedance and etc. will change. In low-frequency, the reservoir will appear in the bottom the video with low-frequency. The velocity of vertical and horizontal wave will change in different situation, and the P-wave velocity decreases significantly, the S-wave velocity changes little. The seismic wave attenuation of the energy will change too, which is also studied in paper. In this study, the methods used of seismic detection and fluid identification include more than 10 types detection methods of seismic attributes of amplitude-type, phase-type, frequency-type, type of absorption attenuation, morphology-type etc. acoustic impedance inversion, velocity inversion, AVO inversion method, low-frequency shad analysis, porosity forecasting technique, reservoir thickness of forecasting method, comprehensive analysis of multi-attribute parameters and seismic numerical simulation of biological reef and bank, and finally we analyze their effectiveness. Methods are in favor of border demarcation of reef and bank reservoir include: root-mean-square amplitude attribute, phase attribute, frequency attribute, main parameters attribute, correlation dimension, morphological type of properties, wave impedance inversion, velocity inversion; methods that are conductive to fluid identification include: wave impedance inversion, velocity inversion, AVO inversion method, low-frequency shade method, frequency attenuation gradient properties, multi-attribute analysis method, and the porosity forecasting method and reservoir thickness forecasting technique are efficiently in indicating the development degree of reservoir. Numerical simulation of seismic method can be used to eliminate the multiple solutions in predicting reef and bank reservoir. The study of more wells in conjunction comparative analysis section can be used to reduce the error that only single-well attribute is used to predict reservoir is filled with oil and gas or not, and it is useful to analyze the environment of the whole area, for the division of seismic facies, for lithology contrast and the reservoir demarcation.All over the words, this study is helpful for experience accumulation of seismic detection and fluid identification in reef and bank reservoir with same seismic and geological condition, and it is the base to forecast reef and bank reservoir precisely.