Dynamics simulation and laws of drilling fluid loss in fractured formations

Well loss is one of the common complex downhole conditions during the drilling in fractured formations. On the basis of fluid dynamics theory, the control equation of fluid loss in 2D rough fractures has been established to basically understand the occurrence mechanism of fluid loss. During the deduction of such equation, drilling fluid is modeled as Bingham fluid and the fracture is described as 2D single fracture with rough surface, index deformation and dip angle. Finite element method is used to solve the fluid loss control equation; based on the created model, the loss laws of drilling fluid in a two-dimension rough fracture has been analyzed. Research results indicate that the smoother the fracture is, the greater the loss rate and the cumulative loss will be; the fracture dip has less impact on loss rate while affects the cumulative loss; the greater the fracture area is, the greater the loss rate and cumulative loss will be; the smaller the fracture length is, the greater the loss rate and cumulative loss will be; the greater the fracture width is, the greater the loss rate and cumulative loss will be; the fluid loss rate and cumulative loss have increased significantly as the downhole pressure difference increases; fluid dynamic shearing stress has less impact on loss rate, but has certain impacts on cumulative loss; the smaller the plastic viscosity is, the greater the loss rate and cumulative loss will be. © 2017, Editorial Office of ACTA PETROLEI SINICA. All right reserved.