Multi-wave Seismic Exploration Technology And Its Application In Reservoir Description

The oil&gas resources in our country are shortage and the new prospecting for large-scale oil&gas fields had not been achieved under the endeavor of several repeated exploration. The recovery rate for oil&gas was lower at the developing oil&gas fields in the whole country. The average standard recovery rate in our country was up to 33. 2%, the lower in eastern regions was up to 28. 7%. The improving recovery rate and making it to rise 1 to 5 percent will be equal to find several new large-scale oil&gas fields. Therefore the research of recovery rate technique is sufficiently significance and is one of the importance research directors in developing oil&gas fields.How to improved recovery rate for oil&gas is a systems engineering and involves in the whole knowledge for reservoirs, reservoir characterization and oil extraction technique. Reservoir characterization technique involves in correct imaging, lithology, physical property and the oil&gas predicting technique for reservoirs. The structure imaging has been achieved using seismic exploration, especially the application of 3D P-wave data and seismic attribution takes effects in reservoir characterization and in search of residual oil.P-wave surveys built based on acoustic wave equation, however, encountered a lot of phenomena and questions appearing along with gradually understanding seismic data, which people cannot explain by using P-wave exploration. The elasticity and anisotropy of media were emerging from exploration practice. The explanations with P-wave seismic data appeared and the display of P-wave data on oil&gas reservoirs existed uncertainly. Consequently multi-wave exploration has been developed.In this paper I simply described how to set up elastic wave equation, solution of wave question, sorting anisotropy, expression for elastic tensor, relations between elastic parameter and anisotropic parameter as well as velocity character in anisotropic media.From investigating the character of multi-wave kinematics and dynamics, we can discover the multi-wave exploration feature. One kind of new multi-wave seismic energy' s distribution in anisotropic media, which went beyond zoeppritz equation, had been introduced in the thesis. For anisotropic media, the PS-wave reflection coefficient can be non-zero when P-wave occurred vertically as long as elastic parameters C₃₄ and/or C₃₅ are non-zero elements.The attenuation mechanism and attenuation character for multi-wave also were described. The presence of gas in fracture increased S-wave attenuation. The presence of water in fracture S-wave attenuation nearly equals to P-wave attenuation. The presence of gas in sandstones increased P-wave attenuation. In oil and water saturated sandstones, S-wave attenuation is higher or nearly equals to P-wave attenuation. On the basis of these principles, we can distinguish gas from water- and oil-saturated rock.The resolution for P-wave and PS-wave is a focus in the early multi-waveexploration, so we compared .the resolution on the theory basis and presented the variation rule of the resolution versus depth for both P-wave and PS-wave. The resolution for both-wave depends on depth.Multi-wave data imaging technique was one of the key techniques in multi-wave exploration. The exact position and structure for reservoirs were surveyed by using the correct processing methods and the reliable basic data were provided for subsequent lithology data processing. Some important PS-wave data processing methods had been introduced in my research work due to the particularity in PS-wave in order to improve imaging quality of multi-wave data, such as suppressed noise, static' s solution for PS-wave data, common converted point gather and anisotropic normal moveout correct methods.The key problem is how can determine the angle between the filed coordinate system and the natural coordinate system when the orientation and strength of fracture in formations are estimated. Under the hypothesis condition of orthogonal polarization of fast and low S-wave, I represented a method to detect the orientation of fracture, that is to say, an expression of angle between the orientation of survey line and the orientation of fracture. The method was demonstrated successfully with synthetic and real data.Ray tracing is one of key techniques in inversion method. I developed a new ray tracing method, which innovated the three-point-disturbing in rectangle cell adapting complex velocity fields, finding the minimum ray-paths and avoiding the shadow zone of ray tracing. This new way called the three-point-Fermat ray-tracing technique. The computed speed of the new ray-tracing method was over 2 times faster than the three-point-disturbing. It also prevented the trouble from choosing quantity of disturbing and was so practicable that I tried for the state patent in early this year.P- and S-wave attenuation and their attenuation ratio had been regarded as the effective means to discriminate the component of fluids. The pioneer research had been made on P- and PS-wave attenuation and their attenuation ratio in this paper. These parameters were applied in discriminating the component of fluids using real multi-wave data.In this paper, with research achievement of multi-wave seismic exploration I mainly analyzed the potential in oil and gas exploitation from-three aspect of structure survey, seismic attribution and fracture parameters. The feasibility had been discussed in detecting reservoirs, searching oil and gas distribution and improving oil recovery with multi-wave seismic exploration in the old oil fields in Chinese central and eastern regions and finally some significant conclusions had been delivered.