| Wangji-Xinzhuang area, located in the Wangji-Xinzhuang nose structure zone, which is in the central and eastern part of the northern slopes of the Biyang Depression, has a good tectonic setting, and is a favorable directional zone of hydrocarbon migration. The area mainly consists of a series of NE-trending faults and a small amount of NW-trending faults. Configuration of intersection faults and tectonic setting lead to the formation of a series of fault blocks and faulted noses, providing trap conditions for accumulation of oil and gas. The sandstone body of Houzhuang delta in the northeast area and of Wangji delta in the northwest area is distribute widely in this area. So the area is favorable for the formation of oil and gas accumulation.Currently, a great discovery has been made in this area that proven oil reserves here is nearly 40 million tons, which mainly distribute in upper member of Eh3. While small proportion of reservoir has been found in underpart member of Eh3, which mainly distribute in western area of Wangji, and none of the geologic reserve in underpart member of Eh3 was found in eastern Wangji and Xinzhuang area. Comprehensive analysis results indicate that reservoir forming condition in upper member of Eh3 is similar to that in underpart member of Eh3. In some wells have been displayed different level evidences of oil and gas in underpart member of Eh3, with a few wells obtaining commercial oil. Underpart member of Eh3 is regarded as the favorable place for hydrocarbon migration and accumulation. The underpart member of Eh3 distribute widely, which was still preserved well after large-scale erosions in upper member of Eh3.However, the current seismic data in Wangji-Xinzhuang region is only able to meet the needs of the shallow seismic exploration and it is difficult to meet the needs of future exploration because of the poor seismic data quality. Due to technological constraints at that time, and in the previous seismic three-dimensional exploration, the upper member of the Eh3 being the exploration target, the existing seismic data from the formation below the member H3 III Sand shows the worse continuity of seismic reflection, low SNR, and poor quality reflection. The imaging of small fault blocks is unclear with low lateral resolution and vertical resolution. Horizon tracking and interpretation of small faults is going with a certain degree of ambiguity and multi-resolution. It is difficult to describe exactly and accurately about the structure of underpart member of Eh3.Therefore, for Wangji-Xinzhuang region, there is a deployment of new acquisition task. Be aimed at the problems such as weak earthquake reflection, low SNR and low-resolution of underpart member of Eh3 in Biyang depression, it is necessary to strive to make technological breakthrough to increase the SNR, continuity and Comparison of accuracy of the seismic data in underpart member of Eh3 in Biyang depression, so as to increase the imaging precision of small fault blocks and beating out the fracture feature of the structure of the small fault blocks.This topic launched a feasibility studies about technical design in acquisition area, we analyzed the main technology and construction difficulty in the survey areas, and systematically analyzed the previous information according to geological tasks and technical requirements. In the base of Reconnaissance of the work area, data collection and analysis of the original three-dimensional data, we proposed feasibility studies and geometry design. Based on fine structure analysis, fault isolation and recognition of translocation system, the pre-stack migration is applied to the high-precision 3D seismic data in this area. Preserving shallow unconformable surface as possible, we increased the SNR of the seismic data and imaging precision of the complex fault, to provide accurate information for structural and lithology interpretation.The main contribution and conclusion are as follows:(1)High precession staggering grid high-order finite-difference algorithm was used in this research. Seismic wave propagation of complex fault belt in Biyang Depression was simulated with two-way wave equation. Then, seismic illumination analysis of multilevel tectonic system of Wangji fault nose structure was complicated, and the geometry system was designed and optimized. The bin size with optimum resolution, the best acquisition position, the maximum and minimum offsets, the arrangement length, and the arrangement rolling are all determined. Thus, it is possible to show the energy distribution in the underground medium, analyze the wave propagating pattern and stratum energy responds, and optimally observe the geological target in complex fault belt, in order to obtain the wave field information as complete and abundant as possible. In the effective range of target strata, this acquisition observation system was similar to high-density with wide-azimuth acquisition in terms of distribution of the offset and the azimuth. Therefore, it is possible to illuminate the underground medium omnidirectionally. In another word, it is favorable to not only the tracing of the shallow layers, but also the imagination of complex fault. Thus, signal to noise ratio of the seismic data was increased, and the tectonic interpretation and lithological exploration can be carried out.(2)After comprehensive judgment based on illumination analysis, the first scheme is commended.24L8S136R204F observation system is used in the south area, and 24L8S144R108F observation system is used in the north area. The signal to noise ratios of target strata below-220m could be accepted, density of the resources were small, the cost was relatively low, the concentration ratio were high, and it was convenient to operate. According to the offset distribution in the first scheme, both the near offset and the far offset were uniformly covered, and the offsets within 200m were almost full-covered. The near offset uniformly coverage was beneficial to the imagination of ultra-shallow layers and unconformities.(3)In the complex fault belt of Biyang, tomographic static correction is more effective than refraction static correction and elevation static correction. The bending and discontinuous events became more natural and fluent, and the signal to noise ratio were increased. After tomographic static correction the shallow events details were abundant, and the frequency were improved. Thus, the effect of in-phase stacking was achieved.(4)The forward operator and conjugate inverse was introduced in this paper. Pre-stack depth migration with shot domain wave equation continuation was completed. This algorithm is stable, and is available for complex velocity field, and the calculation precision is high. The methods were studied, to improve the imaging precision and calculating efficiency of the pre-stack depth migration with shot domain wave equation continuation. Signal fidelity of the migration results were relatively high, seismic reflection characters were obvious, and wave group characteristics of the main layer sections were clear. The geological phenomenon was abundant, and this made the strata tracing simple. The section imagination of small faults was clear, the breakpoint was determined, and the migration was reasonable. In the end, imagination of the fault system was improved obviously, the structural configuration was improved, the events were natural, and both the signal to noise ratio and the continuation were increased.(5)Chopping functions were processed and optimized on floating datum, and high-density acquisition data were used effectively. The effective reflection information of shallow layers was maintained, and the shallow unconformities were clear.(6)The resolution of the results was improved effectively. The frequency band were relatively wide, and the effective reflection frequencies were 5～100Hz. Dominant frequencies of the upper second and third member of Hetaoyuan formation (500ms and the above of the section) reached 45～50Hz. Dominant frequencies of the lower third member of Hetaoyuan formation (700ms～1700ms of the section) reached 30～40Hz. Imagination of the basement was accurate, and the morphology was clear, which were available to do research on regional tectonics, sedimentary evolution, and stress analysis.The innovative points of this paper are as follows:(1)The forward operator and conjugate inverse was introduced in this paper. Pre-stack depth migration with shot domain wave equation continuation was completed. This algorithm is stable, and is available for complex velocity field, and the calculation precision is high. The methods were studied, to improve the imaging precision and calculating efficiency of the pre-stack depth migration with shot domain wave equation continuation. Signal fidelity of the migration results were relatively high, seismic reflection characters were obvious, and wave group characteristics of the main layer sections were clear. The geological phenomenon was abundant, and this made the strata tracing simple. The section imagination of small faults was clear, the breakpoint was determined, and the migration was reasonable. In the end, imagination of the fault system was improved obviously, the structural configuration was improved, the events were natural, and both the signal to noise ratio and the continuation were increased.It is the first time that the wave equation modeling and seismic illumination method applied in the geometry design, the result is very well. The technology meets the requirement of high density, wide azimuth, equal offset and fold number in acquisition parameters. It makes the equal and all azimuth observation of the geological target become reality.
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