Research On Coupling Flowing Characteristics Of Wellbore-fracture Drilling In Carbonate Formation

There are some characteristics of fracture development and abnormal pressure in Deep marine carbonate reservoirs which can easily cause kinds of complex problems of lost,overflow and displacement inflecting exploration and development progress.This thesis's main study wellbore-fracture coupling flow characteristic have been finished through ways of experiement,simulation and theoretical model based flow Mechanism law in fracture and wellbore multiphase flow theory.Main achievements and understandings are as follows:(1)Wellbore-formation visible coupling flow experiment equipment has been manufactured base on 3-D Reconstruction and Visualization Construction of fracture through non-contact measurement system with data collecting and processing.(2)According to the experiment study on flow of two different condition of constant pressure and constant reservoir volume through Wellbore-formation visible coupling flow experiment equipment,the different phenomenons under two conditions are concluded,the relation with pressure of drilling fluid and formation under under different conditions is analyzed by experimental data which can show fluid flow law during gravity replacement of underground fracture.(3)Based on the experimental data and conclusions,the mechanism of gravity displacement is proposed and verified by simulation.The mechanism of gravity displacement of fluid in fracture under different working conditions is further revealed.(4)Based on the mechanism of gravity displacement under constant pressure,the mathematical model of fluid gravity displacement in fracture is established,and the influencing factors of fluid gravity displacement in fracture are analyzed.(5)Drilling rheological models under different temperature and pressure has been established after infected by oil.The well-bore gas-liquid two pahses flow model and well-bore liquid-liquid two phases flow under H-B model of drilling fluid has been established.(6)Wellbore-fracture coupling flow model has been established which can calculate Drilling fluid leakage and formation fluid overflow in gravity displacement through given pressure of wellhead and formation,and also can monitor the annulus pressure.