Dynamic Attitude Simulation Of Marine Seismic Towed Cable

In the face of the increasing demand of human on the petroleum and natural gas along with the global economic growth, developing marine oil and gas resources survey seems more and more important to our country. The marine oil and gas resources survey system is a complicated system which is technology intensive and involves knowledge in different disciplines, in which marine seismic towed cable is one of the key equipment. Current towed cables are mostly three thousand to eight thousand meters long. During the practical process of survey, the stability and validity of signals ask for a certain requirement to the control of towed cable both in depth and horizon, which is not easy for the underwater towed cable in several kilometers long. The crux of solving this problem is to find a way to forecast the attitude of towed cable accurately and master the dynamic characteristics of towed cable.The study object of this thesis is the marine seismic towed cable system. Based on the results of previous researchers, the three- dimensional dynamic model of towed cable was established under certain assumptions; effective algorithm (i.e. box method in space discretization scheme, generalized-a algorithm in temporal discretization scheme) were used to achieve the numerical results. By using the computer simulation technology, the cable attitude and tension distribution in the stable condition and the depth and tension variation of cable in dynamic conditions were studied. In addition, this thesis also makes efforts on the towed cable active control.This thesis analyzed the short-comings of box method in temporal discretization scheme and verified the superiority of using generalized-a algorithm to solve the three-dimensional cable model by case study. Through computer simulation, conclusions of depth and tension variation regularity and characteristics of towed cable in steady straight course, circular manoeuver, speed change of straight run and heaving motion were given, which provide effective basis for cable control studies. According to the dynamics characteristics, ideas about towed cable active control in depth and horizontal direction were put forward and effective horizontal control strategy was designed in this thesis.The methods using to solve the towed cable model and conclusions of simulation in this thesis have certain reference value to marine seismic towed cable study.