Liquid-solid Flow Mechanism In The Fracture Of Carbonate Rock During Well Drilling

Carbonate reservoirs,which are widely distributed,have good physical properties,large reserves and high output,and are easy to form large oil and gas fields,are very important oil and gas resources in the world.The law of liquid-solid two phase flow in carbonate fracture has important guiding significance for fractured leakage,formation overflow,bridge blocking effect in fractured strata,and drilling pressure control in fractured formations.However,there is still a lack of mechanism explanation and theoretical research in petroleum engineering,which leads to the lack of theoretical foundation for engineering problems in drilling in fractured formations.In this paper,the three-dimensional shape of the real carbonate fracture space is reconstructed,and the seepage and numerical simulation of rough fracture surface are carried out based on the drilling conditions.The basic research on the liquid solid two phase flow mechanism and the downhole fracture deformation law in rough fracture is carried out.This study provides a theoretical basis and research ideas for the pressure control,drilling fluid leakage and leakage blocking of fractured formations in drilling process.The specific work and results are as follows:(1)Taking carbonate rock of Shuanghui area in Wangcang,Guangyuan as an example,the fracture of carbonate rock is collected and scanned.Then the fractal dimension of the fracture surface is analyzed.By using the digital fracture,the fissure space flow model and the underground fracture deformation model are established.(2)The fissure space flow model is made into a transparent resin fractured plate.This fractured plate can be used to produce an experimental device to simulate the flow of true carbonate fractures.In this paper,the effects of the size of the particles and the space form of the fractures on the liquid solid two phase flow in the fracture are investigated experimentally.(3)In the aspect of simulation,the structure grid is divided into the fracture flow space model established above,and the simulation method is Euler-Lagrange method.By comparing the simulation results with the experimental results,the causes of the experimental phenomena are analyzed,and the mechanism of liquid solid two phase flow in carbonate rock fractures is revealed.(4)Based on the fracture space flow model and the fracture deformation model,combined with the measured rock mechanics parameters and the underground drilling conditions,the fluid solid coupling deformation model of carbonate fracture is established,and the spatial deformation of fractures caused by fluid on the fracture body acting force is preliminarily studied.Through the above research,this paper provides a theoretical basis and research train of thought for engineering problems such as pressure control,leakage and plugging in fractured formations during drilling.