A Study On The Establishment Of High Precision3-D Space Velocity Field In The Complex Field Containing Special Rock

In the past for a long period, the earth physicists are often use a constant figure represent the speed to constructional drawing. But with the development of the exploration degree, this method also exposed many problems, such as, in the geological condition complex area use a constant figure often appear big structure error, high structure error to offset, low amplitude structure are often neglected, and sometimes even appear false structure, etc. By using the seismic velocity construct a three dimensional velocity field and use variable speed into structure maps can be a solution to these abuses.In the earth geophysical exploration, the speed of the calculating accurate or not directly affects all aspects of seismic exploration and final results, so accurate speed has been a core problem for the seismic exploration. Only by improving the real ability for underground medium speed, can determine the reflected depth of the strata, the dip angle and the position of the strata. Especially in geologic complex area for oil and gas exploration, like our country, under the influence of tectonic movement of different period, had developed various types of special fault, make its underground medium strong anisotropy, speed changes very much. So accurate calculating underground’s speed, and then according to the determination of the accurate speed set up high precision velocity field and get fine structure diagram is geophysical exploration’s one of the important research topics.The accurate speed has been one of the most important factor. Only by improving the real speed for underground medium, we can alter the times of the seismic horizon data into the depth of the strata, distinguish the lithology of the well field and outline the favorable target. In the complex structural area, the transverse and longitudinal velocity change dramatically, there is a low precision when mapping the subsurface structure by constant velocity, we can not identify the illusion which is the uplift in seismic profile for some high-speed rock. The similar defeat of exploration happened in the h71well field located on the steep zone of Honghorsut depression. Due to the circumstance, the paper formulate a set of procedure on the velocity research for the complex structural area where has the special rock.The application of velocity field recovery the real underground form, point out the beneficial direction for the development and reduce the risk of exploration.In this paper, review velocity field and variable speed mapping technology firstly, and analysis of the principle, speed change factors, speed for the detailed discussion, and then based on the theory of knowledge combined with the Honghorsut depression actual situation establish a three dimensional space velocity field, and finally analysis the established the velocity field and variable velocity into structure maps, realize the seismic data conversion from the time domain to the depth field, summed up a set of suitable for the research area in velocity and fine mapping method.According to the research in drilling data and logging data analysis, the study area’s underground develop some types of unstable igneous rock, the speed of the surrounding rock layer was significantly higher than the layer speed, which cause the vertical and horizontal speed changes greatly. In view of the studied geological situation, use the three dimensional space mapping technology and variable speed into the methods figure did a study, use speed spectrum establish velocity field and variable speed into structure maps, and made some achievements and new understanding in the basis of former.In this paper, review velocity field and variable speed mapping technology firstly, and analysis of the principle, speed change factors, speed for the detailed discussion, and then based on the theory of knowledge combined with Honghorsut actual situation establish a three dimensional space velocity field, and finally analysis the established the velocity field and variable velocity into structure maps, realize the seismic data conversion from the time domain to the depth field, summed up a set of suitable for Honghorsut research area in velocity and fine mapping method.Through to the Honghorsut regions’ velocity field research we fine that Honghorsut underground geology condition is very complex, some area have big faults, strata change greatly, lead to underground speed mutations obvious, suit to use the model chromatography method to establish the velocity field and do velocity analysis; By model chromatography method to establish the velocity field must ensure the accuracy of the horizon interpretation; the accurate analysis the Well point and select play a crucial role for velocity field. Using the high accuracy3-d space technology can bring the seismic interpretation results from time domain to high precision geology results maps; The adoption of the velocity spectrum construct the three dimensional space velocity field method is practical, convenience, and high precision, and can satisfy the current geophysical exploration of oil and gas of the seismic accuracy requirement of the speed, use3-d space variable speed mapping technology can achieve seismic data by the time domain depth of field real-time conversion, and has kept the original seismic data of time domain properties, facilitate research on seismic data processing of pre-stack again; old oil field structure research should from the traditional "way line operation" to the modern feedback practices, and constantly adding new development Wells data, and correct treatment, explain the results, especially the velocity change on the influence of the structure maps. If such ability constantly adjust plan, the oil field development would always keep in optimizing state. In old oil fields establish3-d space velocity can help find out the little fault block and small trap and reservoir distribution.