Simulation Of Liquid-solid Two-phase Flow In Rough Wall Fracture

Loss is a complex situation of drilling fluid flowing into the formation from the wellbore through the fracture.The occurrence of loss will not only prolong drilling cycle,cause reservoir damage and economic loss,but also induce complex accidents such as well collapse and blowout,which seriously restrict safe,rapid and efficient drilling and efficient development of oil and gas reservoirs.At present,the loss-proof technology in fracturing formation is mostly focused on the material and process,and the nature of loss needs to be deepened further.Therefore,from the perspective of fluid dynamics,simulation loss dynamics has become the current hot issues,understanding the essence of the loss will help to accurately plugging and loss-proof.Based on fractal theory and Monte Carlo theory,the method of generating rough crack is analyzed,the theoretical formula of generating two-dimensional rough crack is given,the program code of two-dimensional rough crack is written based on MATLAB,and the crack is exponentially deformed,the law of loss is analyzed.Based on the hydrodynamics,the drilling fluid is regarded as a Bingham fluid.The crack is regarded as a two-dimensional single crack with surface roughness,exponential deformation and inclination.The loss control equation of Bingham fluid in the two-dimensional rough fracture is deduced.And the loss control equation is solved by using the prediction-correction method.Finally,the drilling fluid loss simulation software is formed base on the result.Based on the established model,the law of drilling fluid loss in two-dimensional rough fractures was analyzed,and the influence of the roughness,inclination,pressure difference,fluid shear stress,plastic viscosity,particle diameter,particle concentration and sphericalness on the loss rate and the cumulative loss.The results show that the more slippery,the higher the loss rate and the cumulative loss,the smaller the effect of the fracture angle on the loss rate and the cumulative loss.The larger the fracture area is,the bigger the loss rate and the cumulative loss are.The loss rate and accumulative loss increase with the decrease of the fracture length;the bigger the fracture width is,the bigger the loss rate and the accumulated loss are;when the bottom hole pressure difference is larger,the loss rate and cumulative loss increase obviously;Fluid dynamic shear force has little influence on the loss rate and cumulative loss;The smaller the plastic viscosity,the greater the loss rate and cumulative loss.The larger the particle diameter is,the smaller the loss rate and cumulative loss.The larger the particle concentration is,the smaller the loss rate and the cumulative loss.The sphericalness of the particles has little effect on the loss rate and cumulative loss.