Research on the change law of annulus flow pressure loss under the condition of arc concave borehole in cementing

摘要

The exact calculation and control for cementing annulus flow pressure is very important, especially for formations with narrow density windows. It is easy to form belly shaped arc concave boreholes because of the uneven hole enlargement rate in the process of practical drilling. Research on the change law of annulus flow pressure loss in an arc concave borehole is helpful for controlling the annulus pressure profile accurately. The structure of flow pressure loss is analyzed through the establishment of a flow pressure loss equation in an arc concave borehole; the fluid flow control equation is established, the solving method is studied, the analysis software is developed, the flow pressure loss is calculated, the influence law of hole enlargement rate and fluid displacement on the flow pressure loss are analyzed, and the results are verified by numerical simulation software, Fluent. The results show that the flow pressure loss in arc concave borehole sections is less than that in normal boreholes within the scope of common hole enlargement rates. The offset between software calculation results and numerical simulation results are in the scope of engineering allowable error. The conclusions provide a powerful technical reference for analyzing cementing annulus pressure characteristics accurately.