Long horizontal section wells have become an increasingly important technology for the development of unconventional oil and gas resources. In the long horizontal section

severe cuttings bed accumulation with extensive distribution poses a high risk of cuttings-induced pipe sticking. To mitigate the risk

it is crucial to understand the mechanism by which cuttings beds generate resistance on the drill string and accurately quantify such resistance. The traditional linear contact friction model has limited applicability

as it relies on empirical friction coefficients

which does not meet the requirements for precise prediction. Therefore

based on the classical Coulomb friction theory while considering the surface contact relationship between drill string and cuttings bed

a new prediction model for cuttings bed friction has been developed. Sixty-six sets of experiments are conducted using a friction torque measuring device for the rotary drill string to validate the distributed force assumptions in the model and assess its prediction accuracy. The experimental and model prediction results indicate that the surface contact friction theory can explain the resistance exerted by the cuttings bed on the drill string motion. In contrast

the traditional linear contact friction model significantly underestimates the frictional resistance of the cuttings bed. The variation in cuttings bed friction can be divided into three stages

depending on the cuttings accumulation degree

and does not follow a simple linear or exponential trend. As the friction coefficient between cuttings bed and drill string increases

the frictional resistance of the cuttings bed also increases. When the top surface of cuttings bed is above the center of drill string

the cuttings bed density has an influence on the frictional resistance

and it increases as the density rises. The hypothesis of a sinusoidal distribution of normal pressure aligns more closely with the actual conditions. Compared with the experimental results

the average error rate of the predicted values from the final model is 7.56 %

which meets the engineering requirements. The findings indicate that the new cuttings bed friction model can provide valuable guidance for predicting and controlling the frictional resistance and torque of pipe string in drilling and completion operations.