Study On The Theory And Application Of Well Bore Pressure Control Of Complex Drilling Conditions

Along with the developing and innovating of drilling technology,the range of drilling work constantly developed towards all kinds of difficult and complex information. Drilling technology has became more and more complex,but the theoretical model of well control technology did not kept up with it.Those models we used is no longer suitable for complex well,such as deep well、ultra-deep well、extended reach well、MPD etc.Basing on mass conservation and momentum conservation,developing a model of pressure distribution along the hole,to describe the regulation of annulus pressure variation,is a more accurate method than in the past. A lot of Two-Phase flow model,basing on this theoretical system,play an important guiding role in complex well drilling.To improve the accuracy of pressure distribution in annulus,this paper develop a three-phase flow model basing on solid-liquid flow model and gas-liquid flow model. On this way,the developed model could be more close to the actual situation when it is been used to describe the pressure distribution of annulus.This paper also taken into consideration of some complex condition during drilling operation,and optimized the parameter. So that,most para-meters of this model can be collected from state,and few of them is in common use and can be obtained from experiment.As a result,this model not only is more precise,but also has high feasibility and field application promotion.The paper use FDM to solve the model, and use actual data in simulated calculation. The precision of simulated calculation results improved obviously comparing with the traditional model. This indicates that the model can accurately reflect the influence law of complex drill-ing conditions to the well bore pressure distribution. It is can be applied to the construe-tion calculation,and provide a reliable mathematical basis for the implementation of well control operation.