Research On The Real-time Prediction Of The Current Field Of The Gulf Of Beibu Served To The Marine Seismic Exploration Operation

The marine seismic exploration is the main method used in modern marine offshoreoil exploration, the offshore artificial epicentre device emits seismic wave continuously,after seismic wave is incident to the seabed stratam, it will produce a reflection orconverted wave signal when it encounter different geological interface, which will bereceived by the detector and then processed by computer. Then various data reflected theunderground geological structure and oil-gas reservoir by inversion will be getted, whichwill provide a reliable basis for offshore oil exploration. Therefore, to make sure theaccurate position of the detector is of great importance to inverse the position, reserve andstructure of the offshore petroleum resources correctly. And the most changeful current willmake the detector deviate from the original path, route and survey stations, theidentification and arrangement of the position of the detector will be affected, theninfluence the correctness of the various data reflected the underground geological structureand oil-gas reservoir. So the research intends to provide a real-time current numericalprediction model for the marine seismic exploration, to master the current field, work time,towing vessel direction, towing speed and the choice of the inversion coefficient of the seaarea of the seismic exploration and to obtain the best effect of the offshore seismicexploration.Using ECOMSED to build three-dimensional barotropic tidal current numericalmodel of the Gulf of Beibu including the Qiongzhou Strait and taking advantage of theQuikScat satellite wind field data and South China Sea forecast wind field data to calculatetide, tide-induced residual current and tidal current and residual current field forced byrepresentative wind field. The results fitting good with the tidal measured data of theWeizhou Island station guarantees the accuracy of the the simulation results. Through theverification of the tidal current, the rule of the simulation results are very close with that of the measured tidal data. The calculation of the most critical tidal residual current field is inagreement with the calculation results of Cao deming and Fang guohong(1990)basically,which have very good agreement with the results of the20coastal stations, so thisnumerical model can forecast tidal field accurately. Wind current mainly depends on thespatial and temporal resolution of the wind products and the former is most critical,therefore, this research embeds South China Sea forecast wind field data in the model,whose spatial resolution is6minutes.The average velocity of the tide-induced residual current field is1.84cm/s, thevelocity in the middle of the gulf is smaller, while the coast is larger. The wholetide-induced residual current field of the Gulf of Beibu is cyclonic with a smallanticyclonic eddy in the southwest. The direction of the residual current In the west ofHainan Island is northeast basically, and west in the Qiongzhou Strait, where speed islarger. Under the control of the tide, the direction is southwest and southeast during themiddle time of the falling tide and east in the Qiongzhou Strait while northeast andnorthwest during the middle time of the rising tide and west in the Qiongzhou Strait, wherethe miximum of the tide happens.Under the charge of the QuikScat wind field, the direction of the residual current ofthe whole area is southwest in winter, while the coastal current keeps northeast, theaverage speed of the residual current is7cm/s; in summer the direction is southwest in thenorth of the gulf and northwest in the south, the average velocity is4.8cm/s, smaller thanthat in winter. Their tidal current speeds are both larger than that of the tidal current fieldonly charged by the tide.Under the South China Sea forecast wind field, the distribution of the surface residualcurrent field is almost the same with the average distribution of the wind field. The averagevelocity of the residual current of the whole calculation area is2.6cm/s, the maximum is41.1cm/s, located in the east of the Qiongzhou Strait. The speed of the surface tidal currentfield is larger than the middle level and bottom level. The interval of the middle time of thefalling tide and rising tide is about9hours. Verified with measured data, the mean squareerror of velocity is13.4%and the direction is3.74°.This research preliminarily achieves using South China Sea forecast wind field to forecast current field, and has made a comparatively intelligent Human Computer Interface,which is convenient for users to use.