Dynamic cuttings transport law for shallow ultra-deep extended-reach wells in Bohai Sea
In order to further develop oil and gas resources in Bohai Sea,the shallow ultra-deep extended-reach wells in Bohai Oilfield were planned to be implemented,so as to increase the oil drainage area and enhance the output of a single well.However,during the drilling process of large-sized wellbore sections with high inclination in extended-reach wells,it is difficult to clean the wellbore and easy to form the cuttings bed because of the low return velocity of drilling fluid and weak cuttings transport effect,which seriously restricts drilling efficiency and threatens drilling safety.To improve the wellbore cleaning effect,the influence of buoyancy of drilling fluid in the inclined section was introduced,and the calculation method of cuttings mass exchange effect was improved by combining the cuttings diffusion equation.Then,a two-layer dynamic model for cuttings transport in extended-reach wells was established,which could accurately simulate the dynamic transport of cuttings throughout the entire section of extended-reach wells.The case study shows that under the alternating action of drilling and circulation operations,the cuttings bed in extended-reach wells will form a wavy distribution,effectively reducing the excessive accumulation of cuttings in the wellbore.According to the wellbore cleaning effect of Well X in each section,the drilling parameters are optimized.Meanwhile,control measures for the cuttings bed are proposed,including cycle interval and cycle time,providing a theoretical basis for the smooth implementation of shallow ultra-deep extended-reach wells in Bohai Sea.
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