Layout optimization of gathering systems in CBM fields considering three dimensional terrains and obstacles

With the progressive development of CBM fields, the complexity of pipeline networks is increasing dramatically. The design of pipeline network should take environmental factors and reliability into account, since pipeline direction and site selection may be influenced by the terrain reflief and obstacles. In this paper, the optimization of CBM pipeline network was discussed under the conditions of three dimensional terrain with obstacles, depending on the features of "multipoint connection, flexible gathering" and "multiple branches" technologies, and the reliablity of the optimized pipeline network was calculated. Terrains were simulated by means of cubic B spline curve interpolation and obstacle function superposition. The dendritic and radial network connection modes were discussed with the economy of pipeline networks as the objective function and the related gathering conditions as the constraints. Then, four pipeline network layout modes which were established by crossing the two connection modes were compared for their economic feasibility. The reliability of pipeline network was solved after being converted into the reliability of tree network. It is shown that the optimized obstacleavoiding path in three dimensional terrain can shorten the distance, and also reduce the relief of the path, which is essentially different from the obstacle-avoiding path in two dimensional plane that could only increase the distance. The dendritic connection mode is the best in economic feasibility, the radial connection mode is the best in reliablity, and the "radial+dendritic" mode is the best when the ratio of total cost to reliability is taken as an evaluation indicator. Compared with the original modes, the optimized "dendritic+dendritic" mode and "radial+dendritic" mode both are 30% less in construction cost and "dendritic+dendritic" mode is about 29% longer than "radial+dendritic" mode in total pipeline length, verifying the rationality and advantage of the model.