Horizontal Well Cuttings Study Migration Law

Horizontal well technology has become an important means of modern thin layer of oil and gas reservoirs exploration and development, however, higher friction and torque due to poor hole cleaning could cause borehole problems which restricts extending capacity. So in-depth understandings of horizontal section cuttings transport mechanism and dynamic transport model have important practical significance for designing drilling parameters rationally and optimizing drilling parameters and ensuring safe drilling.Actual condition of borehole is a complex media of liquid-solid coupled flow unable to realize visualization in the progress of horizontal well drilling, which causes unclear understanding of liquid-solid flow mechanism and imperfect mathematical description. So, the paper carries out relevant researches using the method of combining theoretical analysis, visual experimental simulation in the ground and CFD simulation.The main contents are as follows:(1) The paper establishes the flow field of horizontal eccentric annulus and conducts some sensitivity analysis of the relevant factors under two conditions of non-rotating drill pipe and drill pipe rotation, then analysis the flow field regularity of the annulus, combining with CFD numerical simulation of flow field in annular.(2) Based on the force acting on the cuttings, the paper establishes the motion equations of single cuttings and simulates trajectory of cuttings with CFD. As a result, the paper researches the internal mechanism of different solid-liquid two-phase flow pattern and different forms of cuttings migration which lay a theoretical foundation for analyzing the conditions of forming cuttings bed.(3) The paper proposes a calculation method for predicting the height of cuttings bed and critical velocity of drilling fluid then performs sensitivity analyzes which could affect the height of cuttings bed which could provide theoretical support for developing programs of hole cleaning.(4) Based on visual cuttings transport experiment, the paper verifies the distribution and migration regularity of cuttings. As a result, the result of critical velocity obtained from experiment is smaller than the result calculated by mathematical model, and the relative tolerance are10.4%and13.1%respectively under two conditions of non-rotating drill pipe and drill pipe rotation which could illustrate the theoretical calculation model in the text can meet the accuracy requirements.Based on the theoretical and experimental study discussed above, the paper forms flow field analysis methods and mathematical description of horizontal annular, besides the theory and regularity about cuttings migration in eccentric horizontal annulus. Moreover, it verifies the formation of liquid-solid coupling flow theory and mathematical description. Finally, it forms a set of measures to improve the level of hole cleaning by the regularity and understanding obtained above.The research can effectively guide the measures of horizontal hole cleaning as well as the design of flow parameters of horizontal wells, so it has a positive significance for ensuring the safety and extending the horizontal wellbore effectively in the progress of horizontal well drilling.