The Study Of Water Trapping Oil Pipeline Pigging Period In Halatang Area

The fluid which oil pipelines in halatang area of Tarim Oilfield transfer is oil with high moisture content,meanwhile the velocity of flow is pretty low.What’s more the area have complex topography and large local topographical height difference.It results that the water is easily traped in low-lying sections of pipeline,which could cause lots of problems.Firstly,pipe is occupied by trapped water so it takes more energy to transport oil.Secondly,trapped water can assist corrosion at inner surface of pipe.At last,it will be danger for downstream equipments if there were too much trapped water in pipeline that beyond the capacity of it when pigging.For these reasons periodically pigging to clear the trapped water is necessary,which leads to another problem that is difficult to develop the cycle.For which will lead to trapped water problem when it is too long or will increase the pigging expenditure when it is too short.To this situation,this paper build a method to seek the best period of pigging base on researching of stagnant water predicting in pipeline.The specific contents are as follows:(1)In order to obtain the settling volume of water drop in oil phase,a forecast model of settling water drop volume is built base on a lognormal distribution function which is established to represent the drop size distribution and verified by lots of experimental data from other researchers,a formula to calculate the settling speed of water drop in oil flow by using Navier Stokes equation,and an empirical equation of others’ experimental data.(2)The identification of flow regime which has significant impact on oil-water flow is a precondition for flow analysis.According to 15 series of experiment data researched by international and domestic academics 4 flow regime prediction models is screened.2 of them is selected to predict the flow pattern in horizon and inclined pipe respectly and the flow regimes of pipes in target area are examed.(3)Comparing with empirical data form many scholars,2 models which do the best among other oil-water flow models are chosen to predict the velocity and volume transport in horizon and inclined pipe respectly.Finally a quasi-steady state model for trapped water volume forecasting is built up based on the models set up above.And a trapped water prediction is done using this model to a typical pipeline with water problem in target area named tasanlian pipeline.The result is contrasted with the simulation results from OLGA software to maintain the validity of this model.(4)In accordance with water condition in pipeline,a pigging cycle making scheme is proposed considering both the economy of pipeline and the safety of downstream equipments,and the cycle of tasanlian pipeline is settled using this method.This study can not only provide a pigging cycle making scheme for pipelines in Tarim Oilfield which have water problem,but also bring up an idea for other pipelines that have same issue.