The Study Of Prestack Time Migration Imaging Factors

With the ripid development of oil and gas exploration, seismic exploration targets become more and more complex, and stack-based poststack time migration no longer meet the imaging needs. Prestack migration technology, which velocity analysis and stack are done on the common imaging point gathers, no longer subject to the impact of diffraction wave and incorrect position of the reflection wave, which avoid the diffusion phenomenon of CMP gathers, therefore, the image quality and precision has been significantly increased and has become a powerful tool for accurate imaging of complex construct. In order to further understand the migration algorithm theory, the relationship between various factors and imaging, this paper carried out the following areas:1.Three kinds of prestack time migration(Kirchhoff integral method, the frequency-wavenumber domain method and finite difference method) principle were briefly introduced and reviewed, and their application scope and merits were compared, which provided a reference for the choice of methods for the migration and application.2.Prestack time migration imaging factors were systematically studied in this paper. Respectively, the acquisition of factors, static correction, signal to noise ratio, resolution, energy, speed and migration parameters were analyzed and evidenced. This paper pointed out the sensitivity of the data body, the dependence of the velocity field and the limitations of the migration parameters for the prestack time migration. And for the mode of action of various factors and characteristics a specific solution were given.3.Quality control methods were studied in this paper. Quality control of imaging software PstmQc1.0 was developed, which make up some functions defects in the processing system. By selecting the evaluation factor, seting evaluation criteria, this paper established a comprehensive evaluation mechanisms to prestack data and outcome quality, and provided a basic judge for the data quality of each step in the procession. 4.According to a Eastern three-dimensional block prestack time migration processing instance, the validity of research were verified. The results show that using this processing and monitoring technology the migration profile have a high signal to noise ratio , obvious reflected wave group characteristics, clear breakpoint position, accurate diffraction wave homing, high purpose layer resolution, which better reflect the structure morphology and stratigraphic structure, and meet the needs of the interpretation and inversion. Thus, imaging factors analysis,quality control methods and this three-dimensional prestack time migration processing flow have obvious application value.Prestack time migration processing is an application technology of combination of theory and experience. Each stage will have an impact on migration imaging. Therefore, studying the influence factors for the imaging, monitoring methods and evaluation tools, for improving the drilling success rate and reduce exploration risk, is of great practical significance and practical value.