Research On Cuttings Migration Law Of Coiled Tube Sidetracking Curved Hole

There are a large number of scattered or unexplored oil reservoirs in the old block.Sidetracking has become an important means for the secondary development of old wells.Among them,coiled tubing sidetracking has fewer restrictions and higher benefits than other sidetracking methods.However,since the annulus space of coiled tube sidetracking is smaller than that of conventional wells,the optimization of drilling parameters is limited,and the effect of drilling fluid in sidetracking boreholes is not good.Under the same working conditions,small annulus boreholes are more likely to cause cuttings settlement.At present,there are few researches on cuttings migration in curved boreholes at home and abroad,and the cuttings migration law in short-radius curved well is unknown.It is necessary to carry out systematic research to understand and improve the cuttings migration law of sidetracking curved boreholes.In this paper,the problem of cuttings migration in the small-sized and large-curvature curved wellbore of coiled tube sidetracking is proposed,and a method of impulsive flow to promote cuttings migration in curved boreholes is proposed.Taking cuttings migration in curved wells as the research object,using numerical calculation methods,the influence of different influencing factors and fixed cuttings bed parameters on cuttings migration in conventional flow and pulse flow is analyzed.Finally,the pulse jet cuttings transport tool was designed and processed;In order to better understand the cuttings deposition state of curved boreholes under different conditions,theoretical analysis and BP neural network model methods are used to analyze and obtain the cuttings volume fraction prediction models of conventional flow and pulse flow.The main work and conclusion of the thesis as follows:(1)Combined with the coiled tube sidetracking parameters,a curved wellbore analysis model was established,and the reliability of the model was verified through the comparison of cuttings migration experiments and numerical calculation results;The effects of cuttings size,wellbore parameters,drilling fluid performance,coiled tubing bending and cuttings bed parameters in curved boreholes on the distribution of cuttings in the borehole and settlement effect are studied.Conventional flow is not effective in removing the cuttings.(2)The effect of different flow waveforms on cuttings migration in sidetracking curved boreholes was comparatively studied by numerical simulation methods,and the trend of cuttings migration in curved boreholes under different pulse flow parameters was analyzed.Finally,while the existence of a fixed cuttings bed in the borehole,the effect of fixed cuttings bed parameters on pulsed cuttings migration is summarized and studied.It is found that the pulse flow has better cleaning ability for a certain amount of cuttings bed.(3)Combining the existing calculation model and analysis results,a dimensional analysis method is used to establish a calculation model for the cuttings volume fraction of wellbore with impulse parameters.In addition,based on the existing calculation results,the BP neural network method is used to obtain a pulsed cuttings volume fraction prediction model suitable for curved boreholes,and the prediction results of the pulsed cuttings calculation model and the BP neural network model are compared.The accuracy of the prediction model was verified and the cuttings prediction model was optimized.Carried out the study of cuttings migration in the curved borehole of coiled tube sidetracking,it provides a reference for the problem of cuttings migration in curved boreholes.