Parameter Optimization Of Drilling Fluid Containing Particles And Study On Rock Breaking Mechanism

The content of this article is divided into two main parts, numerical simulation of flow field of the particle-containing drilling fluid jet bottom hole and failure process with pre-crack rock.Flow field analysis of particle-containing drilling fluid jet is divided into jet performance analysis and incident parameter analysis. This article using the ANSYS Workbench14.0to establish the bottom hole flow model and the discrete phase method for the numerical simulation of the flow field. First, by observing the changes of particle trajectory, velocity vector and pressure distribution parameters, this article analyses the natural jet zone, the impact zone, the back zone, the eddy zone and the overflow zone respectively; second, by studying the discharged particles in flow field and the distribution of pressure and flow field of bottom hole, this article analyses and sums up the impact of the effect on particle drilling by the four basic parameters which are the diameter of small ball, the volume fraction of small ball, pump pressure and confining pressure; last, this article makes the appropriate changes of flow fluid model, analyses the impact of jet performance by drill speed by researching the parameters of flow field pressure, velocity and particle trajectory of the bottom hole, and optimize goal drilling parameters.This article using the ABAQUS nonlinear finite-element software for numerical simulation of failure process with pre-crack rock. Through simulating destruction change of XFEM crack over time, this article finds that the main failure of the rock model under compression load is that crack is crazing along the vertical direction; through the contrast of the maximum principal stress of the rock at different times, undermine the conclusion that30°pre-crack most likely becomes invalid under axial loads, and the time stress grows soon in the30°and45°crack area before and after the crack damage, but0°cracks stress grows faster before failure and slows down after the destruction of stress until smooth; the conclusion of90°cracks is just the opposite to that of other models. Eventually this article learns more about the destruction of the pre-crack rock through finite-element analysis of crack propagation.