The Study Of Wax Deposition Experiment And Prediction Model Of Bohai Oilfield

Currently,experts and scholars from various nations have not yet come to an agreement on the principle of wax deposition.Existing models predicting the deposition profile have general limitations and are not applicable to wax deposition production wells in the Bohai Oilfield.Some of them do not show a comprehensive consideration of the deposition principle.For the field process,the choose of wax removal and control process would depend on the on-site experience.Therefore,research on the law and contributory factors of wax deposition,and models to be built for prognosis of the deposition profile and the effectiveness evaluation of the wax removal and control would play a certain guiding role in the removal and control from the wax deposition and the reasonable exploitation of oil wells.Based on the experimental and theoretical studies,this paper,considering the real production situation in the Bohai Oilfield,gives a model for wax deposition offshore oil wells to compute the fluid temperature and pressure along the wellbore.Solutions to these models tell values of fluid temperature and pressure at different depths.And another model built by analyzed the mechanism of wax deposition for predicting the deposition profile shows the accumulative deposition under various production conditions and indicates influential factors on wax deposition.This paper also conducts a study on the principle of the process on the wax removal and control,and merits,demerits as well as applications of these measures.According to their practical applications to the oilfield,a series of standards and indicators are established to evaluate various processes of the wax removal and control,and a new software is also designed to forecast the dynamic deposition profile and evaluate the measures as well.According to the research findings,wax concentration in the crude oil sample from Bohai Oilfield reach 21.42%,crude wax precipitation point is 38.7?,which should be classified into high wax content oil.The distribution of the fluid temperature and pressure is influenced by the deposition of wax.With the increase of the thickness of the wax layer,the fluid temperature will increase and the fluid pressure will decrease.The calculation results of temperature and pressure distribution model showed a considerably small error compared to the field test results,the calculation error of temperature is 8.97% and that of pressure is 4.92%.The wax deposition profiles calculated by the prediction models are consistent with the cognitions of field production,that the wax depositing rate first increase and then decrease from the bottom to the wellhead.With the expansion of the producing time,the thickness of the deposited wax layer will increase.The variation of production rate,fluid flow velocity and production GOR are the main influence factors for the distribution of wax deposition;conduct wax removal and control evaluation of process measures for 8 wells,quantized evaluation results are consistent with the qualitative understanding of field engineers.The research achievement offers important guidance to the Bohai Oilfield production.