Study On Low-temperature Inhibiting Of Silicate Seawater Drilling Fluid

Natural gas hydrate is a new type of clean energy,and it is a new hope to ensure energy security and curb environmental pollution in the future.However,more than 98% of the natural gas hydrate is stored in the seafloor formation,which causing many difficulties in the commercial exploitation of natural gas hydrates.The study of drilling fluids for gas hydrate formations is a key breakthrough.In view of the difficulties such as poor stability,low temperature,and natural gas hydration regeneration of natural gas hydrate formations,This paper is guided by the drilling requirements,based on theoretical and experimental investigations.Drilling fluid treatment agents have been optimized,and the basic rules of action of hydrate inhibitors have been found.A lowtemperature inhibiting silicate seawater drilling fluid that is highly inhibiting,small filtration loss,and can prevent the formation of natural gas hydrate within 15 hours at 4? and 20 MPa is developed.There are three aspects about the main work and results of this article:(1)The shale suppression of the drilling fluid system is improved to maintain the stability of the well wall.In this paper,the silicate drilling fluid is selected as the design direction.First,the shale expansion experiment is used as the basic method to determine the optimal silicate dosage range,and according to the action principle of various drilling fluid treatment agents,through experiments,The fluid loss control agent,flow pattern regulator and shale inhibitor that play a better role in the silicate drilling fluid system are optimized,and the best ratio is found.(2)Improve the ability of drilling fluid system to resist low temperature.In view of the low temperature environment of the seabed and according to the overall demand of drilling fluids,this paper uses KCl and NaCl as the low temperature resistant materials,takes the viscosity increase of drilling fluid at low temperature relative to normal temperature as the evaluation index,found the influence of KCl and NaCl on the performance of silicate drilling fluid.The results show that "10% KCl + 5% NaCl" can effectively reduce the effect of low temperature on silicate drilling fluid.(3)The performance of natural gas hydrate inhibitors was explored in detail.This paper uses tetrahydrofuran test to conduct a wide range of corative evaluations of hydrate inhibitors.Based on the test,a natural gas hydrate generation simulation instrument is designed and the better hydrates are found.The main influencing factors of the performance of inhibitors and the law of action are discussed.It is believed that the combination of kinetic inhibitor KI-G and thermodynamic inhibitor KCl and NaCl can achieve the best effect.Finally,the formulation of low-temperature inhibiting silicate seawater drilling fluid was formed,which provided references and suggestions for related research on drilling fluid used in natural gas hydrate formations.