| The twenty-first Century is the century of ocean, the contries of the world have will focus on the development of offshore oil and gas resources to the ocean. OBC(Ocean Bottom Cable) is one of the important tools for offshore oil and gas resource exploration. For a long time, our country’s OBC navigation and positioning technology is completely dependent on imports, lack of our own system. In addition, due to the foreign core technology monopoly, the development of this technology in China is lagging behind, our OBC navigation and positioning operation and data processing is still in the level of using operation manual and the company can not carry out the operation under complicated ocean environment. So there is an urgent need for the development of our own OBC navigation and positioning technology in oil and gas exploration.This paper therefore aims at the research of navigation and positioning technology in OBC (Ocean Bottom Cable) seismic operation. It solves the technique problems of operation vessel’s real-time navigation and positioning, OBC cable deployment and control and cable positioning, which used for OBC seismic exploration. Research achievements established a whole navigation and positioning technology and methods for OBC seismic exploration. A OBC integrated navigation and positioning system was developed, and it meets the new demand of OBC seismic exploration under complex environment conditions, and it truly realized the core technology of OBC operation from’Made in China’.The main research work and contributions are as follows:The establishment of a whole complete navigation and positioning technology and method in OBC seismic exploration, it includes the system consitition and work principle of integrated navigation and positioning system, data processing methoed and the positioning accuracy evaluation work in the system.According to the environment complexity of OBC exploration, the attitude correction and reduction methods are put for seismic vessels’s navigation, the corrections change of different sizes of the operation vessels’domestication were analyzed, the experimental data shows the significant influence of wave factors. The sea condition was described by wave spectrum, and it study the rolling and pitch of the vessel by different significant wave height according to the spectrum analysis method, which determined the kalman filter navigation process noise matrix Qk-1and measurement noise covariance matrix Rk, and a different classification based kalman filter modeles are delivered for seismic vessel navigation and control, the decimeter level estimation accuracy of vessel location was realized, it provides a new way for vessel’s high precise navigation and positioning with no attitude sensors.Navigation and positioning data play an important role in the interpretation ofocean bottom seismic datas. But due to the difference of system equipment performance and sampling frequency and the existence of jump data and lack of navigation and positioning observations, it is difficult to obtain the accurate position of gun array at shooting time. A pre-process method based on Polynomial fitting was given to process the raw data, it meets the requirement of cross error detection and synchronization of the data. And interpolation of the observation at the shot time by this mathematic model was presented. A kalman filter-based model to get the individual gun body’s state vector was submitted for gun array navigation and positioning,1meter level positioning accuracy was realized. The strudy results show that it meets the high precision navigation and positioning requirement of marine geophysical exploration in complicated sea conditions.For the probem of OBC cable deployment operation, state and location which will have significant effect on seismic data can not be determined, by means of dynamic model, an ocean bottom cable motion equation under the steady state and an ocean bottom cable motion equation which take into account sea currents were presneted. Compared with the reference literature, the mathematical model established by this paper is more perfect and more consistent with the actual. Using these models, the analyzes of influence of cable shape under the different cable tension, density, resistance coefficient, cable laying speed and fluid density on the profile were presented. The simulation of the motion of the cable in seawater in deployment operation was carried out. The results of the study has important practical significance to the field operation.The paper submitted a systemic research for OBC calbe acoustic positioning method. The analysis showed that the existing Distance Intersection positioning method is complex in the field, and is strictly dependent sound velocity profile and positioning accuracy is low. So a new acoustic positioning method based on the additional depth-constraint was presentd, it can reduce the geometric dilution of precision and realizes the positioning accuracy of1meters. In the addition, take into account the stability of temporal and spatial sound profile, with the help of GPS differential positioning ideas, a new underwater distance differential positioning method which get submeter positioning accuracy was showed in the paper. Compared with the tranditional methoed, it is no need to get sound velocity profile in the field and it greatly simplifies the existing cable positioning operation, and it save operation time and cost. In order to get more accurate cable positioning and more operation efficiency, the researchment for the optimization design of the track of the positioning vessel and track point optimal method were presented. The parallel track line width and S shape line design optimization problem were discussed. It is believed that the parallel track width is1.72times the depth of the water has the minimum GDOP value, S shape track line is better than the parallel trajectory of GDOP, and the total length of the track less than parallel track, and it can improve the working efficiency. Referenced to the GDOP ideas in GPS positioning theory, aiming at the optimization problem of track point. The influence of the number of the track points and acoustic range were discussed, a screening principle of track points was presented which is that track points should be around the transponder symmetrically and evenly distributed, the incident angle of observation to the transponder is in the range of30DEG to60DEG, and the observation range p is in the range of1.155to2.0times the depth of the water. Experiments show that the principle of screening track make up for the lack of eliminating gross error and it improves the accuracy of acoustic positioning.The problems that the current navigation system can not meet the development of HSE(Heath Safety Enviroment) and high effeiciency field production and management are analyzed. A new integrated navigation system based on the multi-vessels distributed architecture was submitted and developed, it is not only includes the deployment navigation, the cable positioning and the synchronized seismic acquisition, but also it meet the requirement of filed operation management and HSE management.In order to check the validity of the data processing method and practicality and completeness of the navigation system, the application in domestic in Bohai Bay and Cameroon project were carried out. It showed that the system realized submetere navigation and positioning accuracy of the operation vessel, the cable positioning accuracy is submeter which is better than first break positioning method. And the cable deployment and control method delievered can give a simulation computation for cable deployment, and it will improve the accuracy of cable deployment in the field. And the new system developed improves the accuracy of synchronous acquisition to50ms and achieves a fleet internal data sharing and visualization to meet the needs of production and safety management in the field. |
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