Study On The Solidifiable Plugging Materials For Drilling Under High Temperature

With the rapid development of modern society,the demand for fossil energy is higher and higher.As an important fossil energy,oil plays an important role in the social energy structure.In order to meet the needs of society and improve oil production,it is necessary to drill deep wells or ultra deep wells to exploit oil.The formation conditions of deep wells or ultra deep wells are complex.With high temperature gradient and pressure gradient,accidents such as drilling fluid loss and blowout often occur.Therefore,it is necessary to use plugging materials that can withstand high temperature and pressure to meet the needs of drilling,improving the efficiency of oil production.The conventional granular-bridging material is not ideal for plugging formation water in micro-fractures,while polymer gel plugging materials are difficult to withstand high temperature,so it is urgent to develop curable plugging materials capable of bearing over 5 MPa and tolerable temperature up to 120 ? to cope with drilling loss under high temperature at present.Epoxy resin can meet the requirements of high temperature and high pressure conditions,which has the three-dimensional network structure formed after curing and has excellent mechanical properties and high temperature resistance.However,the density of epoxy resin itself is low,which can not balance the formation pressure when the formation pressure is too high,which will cause formation water to penetrate into the drilling fluid along with the leakage channel,affecting the performance of the drilling fluid.Therefore,it is necessary to increase the equivalent density of the plugging agent to balance the formation pressure.Barite,as a common weighting agent,is a frequently-used weighting material in drilling engineering.However,the density difference between barite and epoxy resin is large.The introduction of flocs and short fibers to the system can reduce the settlement separation caused by the large difference of density between them.Polyethylene glycol200 is not only a good solvent for curing agent,but also a diluent for reducing the viscosity of epoxy resin.In this paper,bisphenol A and bisphenol F epoxy resins were selected,and ultra-fine dicyandiamide Q-500,4,4 '-diaminodiphenyl sulfone and SH-201 were prepared by ring-opening polymerization of epoxy resin to prepare a curable lost circulation agent suitable for 90 ? 140 ? and curing time of about 3 h.It can enter the lost circulation channel,which can meet the needs of high temperature and high pressure,and prevent the problem of sticking and blocking the borehole due to too fast curing.The compressive strength and temperature resistance of the prepared plugging agent were tested.The results show that the compressive strength of the plugging agent is more than 20 MPa,and the temperature resistance is above 150 ?,which behave good performance of high temperature and high pressure resistance.The results show that the fluidity of plugging agent is close to the fluidity of cement paste,and the settlement stability is excellnet;the mass loss rate of hydrochloric acid,sodium hydroxide and sodium chloride solution is less than 1%,which presents good chemical stability;the viscosity is stable under constant high shear rate and changes with temperature.The fracture surface morphology showed that the introduction of PEG-200 could change the fracture surface state and increase the toughness of the cured epoxy resin.