Research On Drilling Fluid Leakage Prevention Technology For Enhanced Wellbore

In recent years,with the development of dense low-permeability unconventional shale oil and gas fields as a new focus area,micron-sized pore throats have gradually attracted attention.Shale micro-fracture development will make the drilling fluid filtrate into the formation of micro-nano pore throat under thaction of chemical potential or osmotic pressure,the positive pressure differential hydraulic tip is easy to form induced cracks,and then the leakage of the well.In view of shale formation leakage,mature technology and countermeasures have not yet been formed in drilling engineering.Therefore,drilling fluid technology is used to strengthen the purpose of the wellbore to avoid the formation of induced cracks,so as to achieve the leakage prevention effect.research focus.This paper aims at the development characteristics of nano-pores and micro-fissures in weak formations,based on repair defects,preventing "hydraulic splitting",analyzing the characteristics of lost strata,and conducting simulation experiments of drilling fluids in enhanced wellbores.The nanometer-micron drilling fluid materials were selected and the factors affecting the dispersion stability of nanomaterials and the methods of control were explored.The optimal dispersion conditions of nanomaterials were obtained through experimental research.It was concluded through experiments that nano-silica emulsion TSD-H15M was added with 2%anionic surfactant TDL-ND2,and the dispersion was observed microscopically with a laser particle size analyzer to obtain a median diameter of 79nm,and added in the drilling fluid to maintain good nanometer size,is an ideal nano-filler material.Based on the experimental principle of core fracture,the preparation of self-made YLCS-1 core fracturing device and low permeability artificial core was studied and improved.Set up a set of sealed safety,which can accurately reflect the internal micro-crack and micro-pore pressure changes,simulate the change of pore structure within the core,and meet the on-site inspection standards,which is conducive to the observation of the plugging situation from the macroscopic to the microscopic view of a reinforced wellbore Drilling fluid pressure capacity simulation evaluation method.Based on the artificial core,the microstructure of the artificial core was simulated by means of nitrogen adsorption and mercury-immersed SEM.The experimental study was conducted on the formation seal pressure of different nano-water drilling fluids.The experimental results show that nanomaterials have little effect on the performance of drilling fluid,but have a significant impact onthe bearing capacity of the rock and can increase the pressure capacity of the rock by 3 MPa.Nano-materials with emulsified asphalt and polyester micro-particles can further increase the core bearing pressure and core strength.