Study On Pipeline Cleaning Technology Of 24-3 Platform To 23-1 Platform In Xijiang Oilfield

The transmission medium of XJ24-3platform to XJ23-1platform subsea pipeline is oil-water mixed transferring.The wax content of crude oil is26.27mass percent. Due to the thickness of wax deposition in the pipeline is unknown, if wax deposition exists on the pipe wall, the pig will be affected by the shear resistance of wax deposition during moving in the pipeline, and the wax which has been cleared in front of the pig will increase the resistance of the pig. Once the too much cleared wax forms a wax plug, it will affect the safe moving of the Pig.Therefore, in order to ensure the safety of a crude oil pipeline pigging operation, it is critical to analyze the wax deposition situation along the pipeline and pigging operation process and to predict the pigging risk and to choose the appropriate pig and to formulate a perfect and scientific pigging program and an emergency response plan, which can take emergency measures in time when a fault occurs and can ensure the pigging process is scientific, safe and efficient. The paper launched a series of studies to solve the problems. The main work is as follows.(1) The pipe material, routing, transport medium, heat transfer coefficient, wall roughness, ambient temperature, pipe fittings, inspection records and other data have been sort out from design information, run data and historical inspection reports and other information of the pipeline, which can provide a reliable and basic data support for subsequent work of studying wax deposition conditions along the pipeline and analyzing the process of the pig moving and formulating pigging plan.(2) During the studying of the wax deposition situation along the pipeline, the paper firstly uses "activation method" to ensure the wax precipitation point of the oil, and judges that the pipeline has wax deposition tendency, then calculates the thickness of wax deposition along the pipeline. During calculating the thickness of wax deposition, considering the variety of wax deposition model, the paper selects "Huangqi Yu Model" to calculate the wax deposition rate along the pipeline. The theoretical calculation result shows that the wax deposition in the pipeline begins to appear at a distance of8km from the starting point, and with the distance from the starting point increased, the thickness of wax deposition is firstly increased, then it’s decreased from the distance of19km from the starting point.(3) During analyzing the process of the pig moving, the paper firstly chooses the pig suitable for the pipeline pigging operation from several pigs that the scene can provide under the circumstances of the pipeline. Since this pigging operation of the pipeline is in the way of using water to push the pig, and the fluid in front of the pig is solid liquid mixtures containing wax deposition, so the paper corrects the pigging model of crude oil based on the research production of domestic and overseas scholars and the result of studying the wax deposition conditions along the pipeline, and establishes the pigging model suitable for this pipeline situation, then carries out the pigging model to selected pigs at different rate flow of pushing fluid. And the variation regularity of the running speed of different pig and the pressure along the pipe at different rate flow of pushing fluid are obtained, which can provide a reliable data for subsequent work of formulating pigging plan.(4) In the process of pigging risk analysis, since the pigging operation of this pipeline will be carried out after shutdown, the oil temperature will be continuously decreased after shutdown. Once the temperature drops below freezing point(39℃), the crude oil begins to solidify, and the risk of pig blockage will be increased. In addition of analyzing the risk of pig blockage and high pressure, this paper also analyzes the risk of condensation of the crude oil during the pigging process. By analyzing the pigging risk of different pigs, the straight panel pig c is finally chosen.And the suggestions are that the rate flow of pushing fluid should be less than6000m3/d and the pigging operations should be completed in97.22hours after shutdown. Then the operation process of launching and receiving the pig and the emergency procedures are formulated, which can provide a theoretical analysis for the pipeline pigging operations, and farthest ensure the pigging operation is safe and efficient.