New method of predicting surge pressure apply to horizontal well based on casson flow*

摘要

In order to predict the surge pressure caused in the horizontal well drilling process, a new simple and applicable method has been established. It is based on the general theory of hydrostatic drilling fluid mechanics, and specifically described the flowing physical model towards surge pressure in horizontal well annulus, taking the effect of string eccentricity on the flowing law of drilling fluid into consideration. According to the constitutive equation of casson-mode under one-dimensional steady flow and the equations of annular flow rate under different drill string working conditions, this paper introduced the flow rate computation models of axial laminar flow in eccentric annulus apply to horizontal well, of which the numerical model was calculated by the program called Mathematica, ultimately, a new model for surge pressure prediction towards each interval in horizontal well was put forward. Application examples indicated that it can solve questions easily and precisely, which presents important meaning of guidance to the safety control while horizontal well drilling.