The High Precision 3D Seismic Prospecting Techniques In Tuha QL Oilfield

Tuha QL oilfield entered a highly water-bearing production stage, with the production decreasing rapidly and the conflict between reserve and production becoming increasingly acute. On the one hand, the poor 3D seismic leads to incorrect understanding of the distributions of the structures and faults, failing to meet the needs of fine reservoir description. The structure maps used in exploitation are still drafted based on the drilling data, which result in that we do not clearly know the distribution of structure and fault, and the reservoir distribution between wells inside the oilfield, then lead to difficult to predict and adjust the exploitation. On the other hand, it is difficult to increase reserve and productivity in a sustainable manner in the vicinity of the oilfield, unable to compensate for the rapid decrease of oil productivity in this depleted oilfield. Based on above discussion, it is very significant of doing the high precision 3D seismic data acquisition in this area, then making the distribution of small faults and oil-bearing sand-body clear, and providing the high quality seismic data for detailed oil reservoir characterization. However, there are several problems for conducting high accuracy 3D seismic data acquisition in QL Oilfield as follows:(1) Loose surface structure in thick gravel covered area, with weak shooting and receiving signal, and serious seismic attenuation;(2) Many alluvial fans intercrossed together, which leads the tremendous transverse change for surface velocity and thickness. Accordingly, the static correction is a problem for exploration precision;(3) In this area, the data obtained from conventional 3D seismic acquisition can not meet the requirement for further oilfield research because of the following characters: intense structure distortion, complex fault system, and laminated reservoir;(4) Industry interference from many oil facilities inside severely affects the data quality.Regarding so complex surface and subsurface conditions, many new techniques are applied to the 3D seismic operation to increase the data quality: optimizing the 3D geometry, multi-vibrator shooting technique, Broad Band sweep method, flip-flop sweeping technique, splitting Vibroseis sweeps to different VPs, high precision near-surface survey and statics, and setting up Model based noise analysis and suppression. Moreover, through the successive high-resolution data processing and comprehensive research,QL oilfield reservoir character had been gotten to know, exactly the dynamic structure, relationship between oil and water, oil and gas. the 3D framework of the Oilfield were re-built, so that the reliable and high-quality basic information was provided for the second development.