Research On Wax Deposition Model Of Deep-water, High-viscosity And High-pour-point Crude Oil Pipeline

With the increasing demand for oil and gas resources,the exploitation of onshore oil fields has been gradually depleted.The exploitation range of offshore oil fields has also gradually developed from inshore to deep water areas.As a successor to petroleum,deep water,as a result of low temperatures and high pressures in the seabed,limited space for working platforms,difficulties in repairing facilities and high operating costs,has made the oil-gas gathering and transportation environments worse than the coastal waters and has greatly impacted the economic benefits of oilfield development.In response to this question,the term flow assurances was proposed.Among them,multi-phase flow,waxing,hydrate formation control in deep-water and related flow safety technologies all need to be discussed in detail so as to realize the safe and economic development of deep-water oil.In this paper,the problem of waxing in deepwater crude oil pipeline is taken as an entry point,and the waxing problem is modeled and analyzed from the aspects of thermodynamics and kinetics,in order to improve the prediction accuracy of waxing point and waxing rate for deepwater pipeline waxing.Oilfield site operations provide a reference.The main model studies conducted include:(1)For the heavy fraction splitting model,based on the improved six-parameter model,the optimization was further carried out.Using the method of "trial and difference method"for reference,Matlab software was used to compile "Optimum iterative algorithm software for deep sea waxy crude oil heavy fraction splitting node".This simplifies the calculation steps and makes the prediction process more convenient while taking into account the accuracy of the prediction.(2)As the thermodynamic model studies the high-pressure and low-temperature environment of offshore oil,the thermodynamic formula was reconstructed using the Clapeyron equation to reduce the prediction error,and a calculation program was written to quickly obtain the prediction results.(3)As for the dynamic model,the model parameters are adjusted based on the Huang Qiyu model.By observing the data of Congo crude oil in the literature,it is found that there is an approximate linear relationship between the shear stress of the pipe wall and the flow velocity of the pipe flow,so that the shear stress of the pipe wall in the original function is directly replaced by the flow velocity of the pipe flow,and the undetermined parameters are obtained by the non-linear regression analysis.In this paper,the results obtained from the above three groups of models are compared and evaluated with the field or laboratory test data in the literature.Among them,the prediction accuracy of the heavy fraction splitting model and the thermodynamic model are significantly improved compared with the previous models;while the dynamic model has a significant improvement over the Huang Qiyu model,but is 0.7%higher than Gai’ model on AARE.However,The replacement of shear stress with the flow rate of the pipe stream can simplify the process of obtaining the parameters of the offshore oilfield and save the installation cost of complicated equipment.