MODELING HERSCHEL-BULKELY DRILLING FLUID FLOW IN A VARIABLE RADIAL FRACTURE

摘要

A mathematical model of Herschel Bulkely (H-B) drilling fluid flow into a deformable fracture has been established in this work. The finite difference and finite element methods were applied for solving this model. Influence of drilling operating parameters, fracture characteristics, fracture deformation, drilling fluid rheological properties, and mud solids deposition in fractures on the loss behaviors of drilling fluid into the fracture have been investigated by numerical simulation based on the model. It has been found that loss rate and total loss volume may aggravate with increasing drilling differential pressure and loss time. Fracture deformation has a significant impact upon loss rates and total loss volume. The initial aperture and length of fracture are broadened/propagated, correspondingly causing both loss rate and total loss volume increasing. It probed into the characteristics and behaviors of drilling fluids flow in a deformable fracture, carried out the simulation of drilling fluid loss in naturally fractured formations, which can be utilized to accurately describe the mud loss process. New type curves of mud loss obtained by modeling simulation can also be used to evaluate fracture characteristics, diagnose loss types and loss predictions, and also bent production operations by minimizing formation damage.