Analysis on hydraulic adaptability and pressure drop factors of low-pressure pipe network in coal-bed methane field

Abstract

Because the coal-bed methane field is influenced by factors such as low pressure, slow velocity, terrain, and condensed water, which lead to the fact that the design is different from gathering design of conventional gas field, how to make full use of wellhead pressure and maximize the wellhead pressure ability is an important link of surface engineering optimization. Therefore, we need to analyze the factors which influence the pressure drop of the gas-gathering pipe network to improve the efficiency of the coal-bed methane field surface gathering. We first contrasted the two hydraulic analysis software (PIPEPHASE and TGNET) for the analysis of coal seam gas field adaptability. By comparing the simulation results with the actual data, we found that the PIPEPHASE software is better to analyze the hydraulic situation of pipe network in the coal-bed methane field. Then, using PIPEPHASE for network simulation and contrasting the 9 state equations and 26 kinds of pressure drop formula calculation results, SRK state equation and BBM pressure drop formula are recommended. We analyze the inlet temperature, pressure, and other nine factors affecting gas extraction pipeline pressure drop according to the practical experience and put forward the suggestions as follows: (1) in order to reduce the pressure drop and increase the ability of pipeline, burying pipeline under the permafrost and improving the inlet pressure are suggested; (2) The higher the inlet pressure, the more obvious the pipeline efficiency influences the pipeline pressure drop, so the inlet pressure and pipeline efficiency should be reasonably controlled in order to reduce the pressure drop; (3) The higher the pipeline pressure, the greater the wall roughness influences the pipeline pressure drop, also the greater the pressure can damage, so we should try to use small wall roughness materials.