Hole cleaning is one of the key issues in extended reach drilling, the thickness of cutting bed monitor and control is the critical technique which urgent to solve. Based on solid-liquid flow mechanics, considering actions between the layers, slip between solid and liquid phase, and rotation of drill pipe, a three layer dynamic cutting transport model was developed, staggered mesh and Stability Enhancing Two Step method were adopted for the simulation. The influence factors of the thickness of cutting bed were analyzed, ECD with variable cutting bed can be accurately predicted, by compare the measured ECD with the theoretical value, the thickness of cutting bed can be monitored, and this technique has been successfully used in the oil field of South China Sea.

The research results show that high angle hold segment is the most difficult segment for cutting transport. The pump can not reach the minimum flow rate for keeping the hole cleaning. Low viscosity drilling fluid, high flow rate and drill pipe rotation should be adopted, and when the thickness of cutting bed exceeds 10%, flushing method must be used to remove the cuttings, the recommended flushing period is 150m. By this model, the dynamic process of cutting transport during drilling and flushing can be simulated. Giving a guideline to the design of hydraulic parameters, and offering an effective field method to monitor and control the hole cleaning in extended reach well.

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